WO2003018546A2 - Tricyclic pyridin-2-one analogues as ligands for gaba-a receptors - Google Patents

Abstract

A class of selectively substituted fused tricyclic compounds based on a substituted pyridinone moiety are potent and functionally selective ligands for the α2/α3 subunit of the human GABA-A receptor and are thereby effective in the treatment of anxiety.

Description

TRICYCLIC PYRIDIN-2-ONE ANALOGUES AS LIGANDS FOR

GABA-A RECEPTORS

The present invention relates to a class of fused tricyclic compounds based on a substituted pyridone ring, and to their use in therapy. More particularly, this invention is concerned with tricyclic pyridin-2-one analogues which are ligands for GABAA receptors and are therefore useful in the therapy of deleterious mental states.

Receptors for the major inhibitory neurotransmitter, gamma- aminobutyric acid (GABA), are divided into two main classes: (1) GABAA receptors, which are members of the ligand-gated ion channel superfamily; and (2) GABAB receptors, which may be members of the G-protein linked receptor superfamily. Since the first cDNAs encoding individual GABAA receptor subunits were cloned the number of known members of the mammalian family has grown to include at least six α subunits, four β subunits, three γ subunits, one δ subunit, one ε subunit and two p subunits.

Although knowledge of the diversity of the GABAA receptor gene family represents a huge step forward in our understanding of this ligand- gated ion channel, insight into the extent of subtype diversity is still at an early stage. However, the results of various studies (summarised, for example, in WO98/50384) indicate that GABAA receptor agonists which interact more favourably with the oc2 and/or ct3 subunit than with l will be effective in the treatment of anxiety with a reduced propensity to cause sedation. Also, agents which are antagonists or inverse agonists at αl might be employed to reverse sedation or hypnosis caused by αl agonists. The compounds of the present invention, being selective ligands for GABAA receptors, are therefore of use in the treatment and or prevention of a variety of disorders of the central nervous system. Such disorders include anxiety disorders, such as panic disorder with or without agoraphobia, agoraphobia without history of panic disorder, animal and other phobias including social phobias, obsessive-compulsive disorder, stress disorders including post-traumatic and acute stress disorder, and generalized or substance-induced anxiety disorder; neuroses; convulsions; migraine; depressive or bipolar disorders, for example single-episode or recurrent major depressive disorder, dysthymic disorder, bipolar I and bipolar II manic disorders, and cyclothymic disorder; psychotic disorders including schizophrenia; neurodegeneration arising from cerebral ischemia; attention deficit hyperactivity disorder; speech disorders, including stuttering; and disorders of circadian rhythm, e.g. in subjects suffering from the effects of jet lag or shift work.

Further disorders for which selective ligands for GABAA receptors may be of benefit include pain and nociception; emesis, including acute, delayed and anticipatory emesis, in particular emesis induced by chemotherapy or radiation, as well as motion sickness, and post-operative nausea and vomiting; eating disorders, including anorexia nervosa and bulimia nervosa; premenstrual syndrome; muscle spasm or spasticity, e.g. in paraplegic patients; hearing disorders, including tinnitus and age- related hearing impairment; urinary incontinence; and the effects of substance abuse and dependency, including alcohol withdrawal. Selective ligands for GABAA receptors may also be effective as pre-medication prior to anaesthesia or minor procedures such as endoscopy, including gastric endoscopy.

In addition, the compounds in accordance with the present invention may be useful as radioligands in assays for detecting compounds capable of binding to the human GABAA receptor.

EP-A-0183994 relates to bi- and tricyclic pyridone derivatives which are stated to have muscle relaxant, sedative-hypnotic, anxiolytic and/or anticonvulsant activity. WO 98/50384 describes a class of tricyclic pyridin- 2-one analogues, substituted at the 3-position of the pyridone ring by an ester or thiazole moiety, which are stated to be selective ligands for GABAA receptors beneficial in the treatment and/or prevention of neurological disorders, including anxiety and convulsions. There is, however, no disclosure nor any suggestion in EP-A-0183994 or WO 98/50384 of compounds in which the 6-position of the pyridin-2-one moiety is directly linked to a five-membered nitrogen-containing heteroaromatic ring.

The present invention provides a class of tricyclic pyridin-2-one analogues which possess desirable binding properties at various GABAA receptor subtypes. The compounds in accordance with the present invention have good affinity as ligands for the α2 and/or α3 subunit of the human GABAA receptor. The compounds of this invention may interact more favourably with the α2 and/or α3 subunit than with the αl subunit. Desirably, the compounds of the invention will exhibit functional selectivity in terms of a selective efficacy for the α2 and/or α3 subunit relative to the αl subunit. The compounds of the present invention are GABAA receptor subtype ligands having a binding affinity (Ki) for the α2 and/or α3 subunit, as measured in the assay described hereinbelow, of 100 nM or less, typically of 50 nM or less, and ideally of 10 nM or less. The compounds in accordance with this invention may possess at least a 2-fold, suitably at least a 5-fold, and advantageously at least a 10-fold, selective affinity for the α2 and/or α3 subunit relative to the αl subunit. However, compounds which are not selective in terms of their binding affinity for the α2 and/or α3 subunit relative to the αl subunit are also encompassed within the scope of the present invention; such compounds will desirably exhibit functional selectivity in terms of a selective efficacy for the α2 and/or α3 subunit relative to the αl subunit.

The present invention provides a compound of formula I, or a salt or iV-oxide thereof:

(I)

wherein

E represents -(CH2)n-; n is 1, 2 or 3;

Q represents the residue of an imidazole or triazole ring; R¹ and R² independently represent hydrogen, hydrocarbon, a heterocyclic group, halogen, cyano, trifiuoromethyl, nitro, -OR , -OCOR^a, -OS0₂R^a, -SR^a, -SOR^a, -S0₂R^a, -S0₂NR^aR^b, -NR^aR^b, -NR^aCOR , -NR^aC0₂R^b, -COR^a, -C0₂R^a or -CONR^aR^b;

R³ represents hydrogen or Ci-β alkyl; and

R and R^b independently represent hydrogen, hydrocarbon or a heterocyclic group.

For use in medicine, the salts of the compounds of formula I will be pharmaceutically acceptable salts. Other salts may, however, be useful in the preparation of the compounds according to the invention or of their pharmaceutically acceptable salts. Suitable pharmaceutically acceptable salts of the compounds of this invention include acid addition salts which may, for example, be formed by mixing a solution of the compound according to the invention with a solution of a pharmaceutically acceptable acid such as hydrochloric acid, sulphuric acid, methanesulphonic acid, fumaric acid, maleic acid, succinic acid, acetic acid, benzoic acid, oxalic acid, citric acid, tartaric acid, carbonic acid or phosphoric acid. Furthermore, where the compounds of the invention carry an acidic moiety, suitable pharmaceutically acceptable salts thereof may include alkali metal salts, e.g. sodium or potassium salts; alkaline earth metal salts, e.g. calcium or magnesium salts; and salts formed with suitable organic ligands, e.g. quaternary ammonium salts.

The term "hydrocarbon" as used herein includes straight-chained, branched and cyclic groups containing up to 18 carbon atoms, suitably up to 15 carbon atoms, and conveniently up to 12 carbon atoms. Suitable hydrocarbon groups include Ci-β alkyl, C2-6 alkenyl, C2-6 alkynyl, C3-7 cycloalkyl, C3-7 cycloalkyl(Cι-6)alkyl, indanyl, aryl, aryl(Cι-6)alkyl, aryl(C₂-6)alkenyl and aryl(C2-6)alkynyl.

The expression "a heterocyclic group" as used herein includes cyclic groups containing up to 18 carbon atoms and at least one heteroatom preferably selected from oxygen, nitrogen and sulphur. The heterocyclic group suitably contains up to 15 carbon atoms and conveniently up to 12 carbon atoms, and is preferably linked through carbon. Examples of suitable heterocyclic groups include C3-7 heterocycloalkyl, C3-7 heterocycloalkyl(Cι-6)alkyl, heteroaryl and heteroaryl(Cι-6)alkyl groups.

Suitable alkyl groups include straight-chained and branched alkyl groups containing from 1 to 6 carbon atoms. Typical examples include methyl and ethyl groups, and straight-chained or branched propyl, butyl and pentyl groups. Particular alkyl groups are methyl, ethyl, n.-propyl, isopropyl, isobutyl, tert-h tyl and 2,2-dimethylpropyl. Derived expressions such as "Ci-β alkoxy", "C1-6 alkylamino" and "Ci-β alkylsulphonyl" are to be construed accordingly.

Suitable alkenyl groups include straight-chained and branched alkenyl groups containing from 2 to 6 carbon atoms. Typical examples include vinyl, allyl and dimethylailyl groups.

Suitable alkynyl groups include straight-chained and branched alkynyl groups containing from 2 to 6 carbon atoms. Typical examples include ethynyl and propargyl groups.

Suitable cycloalkyl groups include groups containing from 3 to 7 carbon atoms. Particular cycloalkyl groups include cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl. Typical examples of C3-7 cycloalkyl(Cι-6)alkyl groups include cyclopropylmethyl, cyclohexylmethyl and cyclohexylethyl.

Particular indanyl groups include indan-1-yl and indan-2-yl.

Particular aryl groups include phenyl and naphthyl, especially phenyl.

Particular aryl(Cι-6)alkyl groups include benzyl, phenylethyl, phenylpropyl and naphthylmethyl, especially benzyl or phenylethyl.

A particular aryl(C_2-6)alkenyl group is phenylethenyl.

A particular aryl(C₂-6)alkynyl group is phenylethynyl. Suitable heterocycloalkyl groups include azetidinyl, pyrrolidinyl, piperidinyl, piperazinyl and morpholinyl groups.

A particular C3-7 heterocycloalkyl(Cι-6)aιkyl group is pyr r olidinylethyl .

Suitable heteroaryl groups include pyridinyl, quinolinyl, isoquinolinyl, pyridazinyl, pyrimidinyl, pyrazinyl, pyranyl, furyl, benzofuryl, dibenzofuryl, thienyl, benzthienyl, pyrrolyl, indolyl, pyrazolyl, indazolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, imidazolyl, benzimidazolyl, oxadiazolyl, thiadiazolyl, triazolyl and tetrazolyl groups.

The expression "heteroaryl(Cι-6)alkyl" as used herein includes furylmethyl, furylethyl, thienylmethyl, thienylethyl, oxazolylmethyl, oxazolylethyl, thiazolylmethyl, thiazolylethyl, imidazolylmethyl, imidazolylethyl, oxadiazolylmethyl, oxadiazolylethyl, thiadiazolylmethyl, thiadiazolylethyl, triazolylmethyl, triazolylethyl, tetrazolylmethyl, tetrazolylethyl, pyridinylmethyl, pyridinylethyl, pyrimidinylmethyl, pyrazinylmethyl, quinolinylmethyl and isoquinolinylmethyl.

The hydrocarbon and heterocyclic groups may in turn be optionally substituted by one or more groups selected from Ci-β alkyl, C3-7 cycloalkyl, adamantyl, phenyl, benzyl, halogen, C1-6 haloalkyl, Ci-β hydroxyalkyl, Ci-β aminoalkyl, trifluoromethyl, hydroxy, Ci-β alkoxy, aryloxy, keto, Cι-3 alkylenedioxy, nitro, cyano, carboxy, C2-6 alkoxycarbonyl, C_2-6 alkoxycarbonyl(Cι-6)alkyl, C₂-β alkylcarbonyloxy, arylcarbonyloxy, aminocarbonyloxy, formyl, C_2-β alkylcarbonyl, arylcarbonyl, Cι-6 alkylthio, Ci-β alkylsulphinyl, Ci-β alkylsulphonyl, arylsulphonyl, -NR^VR^W, -NR^vCOR^w, -NR^vC0₂R^w, -NR^vS0₂R^w, -CH₂NR^vS0₂R^w, -NHCONR^vR^w, -CONRvRw, -S0₂NR^vR^w and -CH₂S0₂NR^vR^w, in which R^v and R independently represent hydrogen, Ci-β alkyl, aryl or aryl(Cι-6)alkyl.

The term "halogen" as used herein includes fluorine, chlorine, bromine and iodine, especially fluorine or chlorine.

Where the compounds according to the invention have at least one asymmetric centre, they may accordingly exist as enantiomers. Where the compounds according to the invention possess two or more asymmetric centres, they may additionally exist as diastereoisomers. It is to be understood that all such isomers and mixtures thereof in any proportion are encompassed within the scope of the present invention.

Specific embodiments of the compounds according to the invention include the compounds of formula IA, IB, IC and ID, and salts and N- oxides thereof:

R°

wherein E, R¹, R² and R³ are as defined above.

Preferably, n represents 2 or 3, especially 3.

Suitably, R¹ represents aryl or heteroaryl, either of which groups may be optionally substituted.

Illustrative values of R¹ include phenyl, furyl, thienyl, thiazolyl and thiadiazolyl, any of which groups may be optionally substituted.

Suitably, R¹ is unsubstituted or monosubstituted. Examples of typical substituents on R¹ include Ci-β alkyl, C3-7 cycloalkyl and halogen. Examples of specific substituents on R¹ include methyl, cyclopropyl and chloro. Particular values of R¹ include phenyl, furyl, thienyl, thiazolyl

(especially thiazol-2-yl), methylthiazolyl (especially 4-methylthiazol-2-yl or 2-methylthiazol-4-yl), cyclopropylthiazolyl (especially 4-cyclopropylthiazol- 2-yl), chlorothiazolyl (especially 4-chlorothiazol-2-yl) and methylthiadiazolyl (especially 3-methyl-[l,2,4]thiadiazol-5-yl). Suitably, R² represents hydrocarbon, a heterocyclic group, halogen, -

OR^a, -NR^aR^b or -C0₂R^a, in which R^a and R^b are as defined above. Typically, R² represents aryl or heteroaryl, either of which groups may be optionally substituted; or halogen, -OR^a, NR^aR^b or -C0₂R^a, in which R^a and R^b are as defined above.

Suitable values of R^a include Cι-6 alkyl, C3-7 cycloalkyl, aryl(Cι-6)alkyl, C3-7 heterocycloalkyl(Cι-δ)alkyl and heteroaryl(Cι-6)alkyl, any of which groups may be optionally substituted.

Illustrative values of R^a include methyl, cyclobutyl, benzyl, phenylethyl, pyrrolidinylethyl, imidazolylmethyl, triazolylmethyl and pyridinylmethyl, any of which groups may be optionally substituted. Suitably, R^a is unsubstituted or monosubstituted. Examples of typical substituents on R^a include Ci-β alkyl and aryl(Cι-6)alkyl, especially methyl or benzyl.

Specific values of R^a include methyl, cyclobutyl, benzyl, phenylethyl, pyrrolidinylethyl, methylimidazolylmethyl, benzyltriazolylmethyl and pyridinylmethyl.

Typical values of R^b include hydrogen and Ci-β alkyl, especially hydrogen or methyl.

Where R² represents aryl or heteroaryl, the requisite group may be unsubstituted, or substituted by one or more substituents. Typically, R² may be unsubstituted, or substituted by one or more substituents. More particularly, R² may be unsubstituted or monosubstituted. Examples of typical substituents on the group R² include Ci-β alkyl, phenyl, benzyl, halogen, Ci-β hydroxyalkyl, trifluoromethyl, Cι-6 alkoxy, C1-3 alkylenedioxy, cyano, formyl, C_2-6 alkylcarbonyl, -NR^VR^W and -NR^vCOR^w, in which R^v and R^w are as defined above.

Suitably, R^v is hydrogen.

Typical values of R^w include hydrogen and Ci-β alkyl, especially hydrogen or methyl.

Examples of specific substituents on R² include methyl, phenyl, benzyl, fluoro, chloro, hydroxymethyl, trifluoromethyl, methoxy, methylenedioxy, cyano, formyl, acetyl, amino and acetylamino. Representative values of R² are typified by phenyl, pyridin l or thienyl, any of which groups may be optionally substituted; or halogen, -OR^a, -NR^aR^b or -C0 R^a, in which R^a and R^b are as defined above.

Individual values of R² include phenyl, methylphenyl, biphenylyl, difluorophenyl, (chloro)(fluoro)phenyl, chlorophenyl, dichlorophenyl, hydroxymeth l-phenyl, trifluoromethyl-phenyl, methoxyphenyl, methylenedioxyphenyl, cyanophenyl, formylphenyl, acetylphenyl, aminophenyl, acetylamino-phenyl, pyridinyl, thienyl, iodo, ethoxy, cyclobutyloxy, benzyloxy, pyrrolidinyl-ethoxy, methylimidazolyl-methoxy, benzyltriazolyl-methoxy, benzylamino, iV-benzyl-iV-methylamino, phenylethylamino, pyridinylmethylamino and methoxycarbonyl.

Particular values of R³ include hydrogen and methyl.

In a preferred embodiment, R³ is hydrogen.

In another embodiment, R³ is methyl.

A particular sub-class of compounds according to the invention is represented by the compounds of formula II, and pharmaceutically acceptable salts and iV-oxides thereof:

(ID

wherein

X represents oxygen or sulphur;

Y and Z independently represent CH or nitrogen;

R¹¹ represents hydrogen, Ci-β alkyl, C3-7 cycloalkyl or halogen; and

Q, R² and R³ are as defined above.

In a preferred embodiment, X is sulphur. In another embodiment, X is oxygen. In one embodiment, Y is CH. In another embodiment, Y is nitrogen. In one embodiment, Z is nitrogen. In another embodiment, Z is CH. In one embodiment, X is oxygen or sulphur, and Y and Z are both

CH. In another embodiment, X is sulphur, Y is CH and Z is nitrogen.

In a further embodiment, X is sulphur, and Y and Z are both nitrogen.

Suitable values of R¹¹ include hydrogen, methyl, cyclopropyl and chloro. In a favoured embodiment, R¹¹ is methyl. Specific compounds within the scope of the present invention include those compounds tabulated in the accompanying Examples; and salts and iV-oxides thereof.

Also provided by the present invention is a method for the treatment and/or prevention of anxiety which comprises administering to a patient in need of such treatment an effective amount of a compound of formula I as defined above or a pharmaceutically acceptable salt thereof.

Further provided by the present invention is a method for the treatment and/or prevention of convulsions (e.g. in a patient suffering from epilepsy or a related disorder) which comprises administering to a patient in need of such treatment an effective amount of a compound of formula I as defined above or a pharmaceutically acceptable salt thereof.

The binding affinity (Ki) of the compounds according to the present invention for the α3 subunit of the human GABAA receptor is conveniently as measured in the assay described hereinbelow. The α3 subunit binding affinity (K of the compounds of the invention is ideally 10 nM or less, preferably 2 nM or less, and more preferably 1 nM or less.

The compounds according to the present invention will ideally elicit at least a 40%, preferably at least a 50%, and more preferably at least a 60%, potentiation of the GABA EC₂o response in stably transfected recombinant cell lines expressing the o3 subunit of the human GABA_A receptor. Moreover, the compounds of the invention will ideally elicit at most a 30%, preferably at most a 20%, and more preferably at most a 10%, potentiation of the GABA EC₂o response in stably transfected recombinant cell lines expressing the αl subunit of the human GABAA receptor.

The potentiation of the GABA EC₂o response in stably transfected cell lines expressing the α3 and αl subunits of the human GABAA receptor can conveniently be measured by procedures analogous to the protocol described in Wafford et al., Mol. Pharmacol., 1996, 50, 670-678. The procedure will suitably be carried out utilising cultures of stably transfected eukaryotic cells, typically of stably transfected mouse Ltk- fibroblast cells.

The compounds according to the present invention exhibit anxiolytic activity, as may be demonstrated by a positive response in the elevated plus maze and conditioned suppression of drinking tests (cf. Dawson et al., Psychopharmacology, 1995, 121, 109-117). Moreover, the compounds of the invention are substantially non-sedating, as may be confirmed by an appropriate result obtained from the response sensitivity (chain-pulling) test (cf. Bayley et al., J. Psychopharmacol., 1996, 10, 206-213).

The compounds according to the present invention may also exhibit anticonvulsant activity. This can be demonstrated by the ability to block pentylenetetrazole-induced seizures in rats and mice, following a protocol analogous to that described by Bristow et al. in J. Pharmacol. Exp. Ther., 1996, 279, 492-501.

In order to elicit their behavioural effects, the compounds of the invention will ideally be brain-penetrant; in other words, these compounds will be capable of crossing the so-called "blood-brain barrier". Preferably, the compounds of the invention will be capable of exerting their beneficial therapeutic action following administration by the oral route.

The invention also provides pharmaceutical compositions comprising one or more compounds of this invention in association with a pharmaceutically acceptable carrier. Preferably these compositions are in unit dosage forms such as tablets, pills, capsules, powders, granules, sterile parenteral solutions or suspensions, metered aerosol or liquid sprays, drops, ampoules, auto-injector devices or suppositories; for oral, parenteral, intranasal, sublingual or rectal administration, or for administration by inhalation or insufflation. For preparing solid compositions such as tablets, the principal active ingredient is mixed with a pharmaceutical carrier, e.g. conventional tableting ingredients such as corn starch, lactose, sucrose, sorbitol, talc, stearic acid, magnesium stearate, dicalcium phosphate or gums, and other pharmaceutical diluents, e.g. water, to form a solid prefor ulation composition containing a homogeneous mixture of a compound of the present invention, or a pharmaceutically acceptable salt thereof. When referring to these preformulation compositions as homogeneous, it is meant that the active ingredient is dispersed evenly throughout the composition so that the composition may be readily subdivided into equally effective unit dosage forms such as tablets, pills and capsules. This solid preformulation composition is then subdivided into unit dosage forms of the type described above containing from 0.1 to about 500 mg of the active ingredient of the present invention. Typical unit dosage forms contain from 1 to 100 mg, for example 1, 2, 5, 10, 25, 50 or 100 mg, of the active ingredient. The tablets or pills of the novel composition can be coated or otherwise compounded to provide a dosage form affording the advantage of prolonged action. For example, the tablet or pill can comprise an inner dosage and an outer dosage component, the latter being in the form of an envelope over the former. The two components can be separated by an enteric layer which serves to resist disintegration in the stomach and permits the inner component to pass intact into the duodenum or to be delayed in release. A variety of materials can be used for such enteric layers or coatings, such materials including a number of polymeric acids and mixtures of polymeric acids with such materials as shellac, cetyl alcohol and cellulose acetate. The liquid forms in which the novel compositions of the present invention may be incorporated for administration orally or by injection include aqueous solutions, suitably flavoured syrups, aqueous or oil suspensions, and flavoured emulsions with edible oils such as cottonseed oil, sesame oil, coconut oil or peanut oil, as well as elixirs and similar pharmaceutical vehicles. Suitable dispersing or suspending agents for aqueous suspensions include synthetic and natural gums such as tragacanth, acacia, alginate, dextran, sodium carboxymethylcellulose, methylcellulose, polyvinyl-pyrrolidone or gelatin.

In the treatment of anxiety, a suitable dosage level is about 0.01 to 250 mg/kg per day, preferably about 0.05 to 100 mg kg per day, and especially about 0.05 to 5 mg/kg per day. The compounds may be administered on a regimen of 1 to 4 times per day.

The compounds in accordance with the present invention may be prepared by a process which comprises cyclising a compound of formula III:

(HI)

wherein E, Q, R¹, R² and R³ are as defined above, and L¹ represents a readily displaceable group. The readily displaceable group L¹ is suitably hydroxy, in which case the cyclisation is conveniently carried out by treating the compound of formula III with triphenylphosphine in the presence of diethyl azodicarboxylate (DEAD), typically in an inert solvent such as tetrahydrofuran or dichloromethane. In an alternative procedure, the compounds in accordance with the present invention may be prepared by cyclising a compound of^" formula IV:

(IV)

wherein E, Q, R¹, R² and R³ are as defined above and L² represents a readily displaceable group.

The readily displaceable group L² is suitably a halogen atom, e.g. chloro, in which case the cyclisation of compound rV is conveniently effected by treatment with a base such as sodium hydride, typically in a solvent such as iV,.N-dimethylformamide or acetonitrile.

Where L² represents chloro, the requisite compound of formula TV may be prepared from the corresponding compound of formula IV wherein L² represents hydroxy by treatment with thionyl chloride.

The intermediates of formula III may be prepared by reacting a compound of formula V with a compound of formula VI:

(V) (VI)

wherein E, Q, R¹, R², R³ and L¹ are as defined above.

The reaction between compounds V and VI is conveniently effected by treatment with a base, e.g. sodium hydride, typically in the presence of sodium methoxide, suitably in a solvent such as iV^iV-dimethylformamide. Similarly, the intermediates of formula TV may be prepared by reacting a compound of formula VII with a compound of formula VIII:

(VII) (VIII)

wherein E, Q, R¹, R², R³ and L² are as defined above.

The reaction between compounds VII and VIII is conveniently effected by treatment with a base such as sodium hydride, typically in a solvent such as iV,iV-dimethylformamide. The intermediates of formula V and VII may be prepared by reacting iV^iV-dimethylformamide dimethyl acetal with, respectively, the corresponding compound of formula IX or X:

(IX) (X)

wherein E, Q, R², R³ and L¹ are as defined above.

The intermediates of formula IX may be prepared by reacting a compound of formula XI with a compound of formula XII:

wherein E, Q, R², R³ and L¹ are as defined above.

The reaction between compounds XI and XII is conveniently effected by treatment with a base such as w-butyllithium, typically in tetrahydrofuran at -78°C.

Where they are not commercially available, the intermediates of formula VI, VIII, X, XI and XII may be prepared by methods analogous to those described in the accompanying Examples, or by standard methods well known from the art.

It will be understood that any compound of formula I initially obtained from any of the above processes may, where appropriate, subsequently be elaborated into a further compound of formula I by techniques known from the art. For example, a compound of formula I initially obtained wherein R² represents benzyloxy may be converted into the corresponding compound of formula I wherein R² represents aryl, aryl(C₂-6)alkenyl or aryl(C_2-6)alkynyl by a stepwise process which comprises debenzylation using boron tribromide in dichloromethane; treatment of the resulting hydroxy compound with trifluoromethanesulphonic anhydride in the presence of pyridine or lutidine to afford the corresponding triflate derivative; and reaction of the latter compound with the appropriate aryl or aryl(C2-β)alkenyl boronic acid in the presence of tetrakis(triphenylphosphine)palladium(0) and potassium phosphate or sodium carbonate, or with the appropriate aryl(C_2- β)alkyne in the presence of bis(triphenylphosphine)palladium(II) chloride, triethylamine and iV,iV-dimethylformamide, to obtain the desired product of formula I. Moreover, a compound of formula I initially obtained wherein R² represents benzyloxy may be converted into the corresponding compound of formula I wherein R² represents heteroaryl(Cι-6)alkyl by debenzylation as described above followed by treatment of the resulting hydroxy compound with an alkylating agent, for example a heteroaryl(Cι-6)alkyl halide such as 3-picolyl chloride, typically in the presence of sodium hydride in a solvent such as iV,iV-dimethylformamide. A compound of formula I wherein R² represents benzyloxy may be converted into the corresponding compound of formula I wherein R² represents -OR^a by debenzylation as described above followed by treatment of the resulting hydroxy compound with an alcohol of formula R^a-OH, typically in the presence of triphenylphosphine and DEAD. A compound of formula I wherein R² is nitro may be reduced by catalytic hydrogenation to afford the corresponding compound of formula I wherein R² is amino, and this compound may in turn be alkylated by treatment with the appropriate aldehyde in the presence of a reducing agent such as sodium cyanoborohydride. A compound of formula I wherein R² represents -NHR^b may also be alkylated by treatment with the appropriate aldehyde in the presence of a reducing agent such as sodium cyanoborohydride. Additionally, a compound of formula I wherein R² is amino may be converted into the corresponding compound wherein R² is iodo by diazotisation in the presence of sodium nitrite followed by treatment with potassium iodide. The resulting iodo derivative may then be converted into the corresponding compound wherein R² is aryl by treatment with the appropriate aryl boronic acid and a transition metal catalyst such as tetrakis(triphenyl)phosphine(0), typically in the presence of potassium phosphate; or it may be converted into the corresponding alkyl ester derivative, i.e. a compound of formula I wherein R² represents alkoxycarbonyl, e.g. methoxycarbonyl, by treatment with carbon monoxide and the appropriate alkanol, e.g. methanol, in the presence of diisopropylethylamine (Hunig's base), l,3-bis(diphenylphosphino)propane (DPPP) and palladium(II) acetate. A compound of formula I wherein R³ represents hydrogen may be converted into the corresponding compound wherein R³ represents Ci-β alkyl by treatment with the appropriate alkyl halide, e.g. methyl iodide, typically in the presence of a base such as n- butyllithium. Where the above-described processes for the preparation of the compounds according to the invention give rise to mixtures of stereoisomers, these isomers may be separated by conventional techniques such as preparative chromatography. The novel compounds may be prepared in racemic form, or individual enantiomers may be prepared either by enantiospecific or enantioselective synthesis or by resolution. The novel compounds may, for example, be resolved into their component enantiomers by standard techniques such as preparative HPLC, or the formation of diastereomeric pairs by salt formation with an optically active acid, such as (-)-di-p-toluoyl-d-tartaric acid and/or (+)-di-p-toluoyl-l-tartaric acid, followed by fractional crystallization and regeneration of the free base. The novel compounds may also be resolved by formation of diastereomeric esters or amides, followed by chromatographic separation and removal of the chiral auxiliary.

During any of the above synthetic sequences it may be necessary and/or desirable to protect sensitive or reactive groups on any of the molecules concerned. This may be achieved by means of conventional protecting groups, such as those described in Protective Groups in Organic Chemistry, ed. J.F.W. McOmie, Plenum Press, 1973; and T.W. Greene & P.G.M. Wuts, Protective Groups in Organic Synthesis, John Wiley & Sons, 1991. The protecting groups may be removed at a convenient subsequent stage using methods known from the art.

The following Examples illustrate the preparation of compounds according to the invention.

The compounds in accordance with this invention potently inhibit the binding of [³H]-flumazenil to the benzodiazepine binding site of human GABAA receptors containing the α2 or α3 subunit stably expressed in Ltk- cells.

Reagents • Phosphate buffered saline (PBS).

• Assay buffer: 10 mM KH2PO4, 100 mM KC1, pH 7.4 at room temperature. <» [³H]-Flumazenil (18 nM for αlβ3γ2 cells; 18 nM for α2β3γ2 cells; 10 nM for α3β3γ2 cells) in assay buffer.

• Flunitrazepam 100 μM in assay buffer. • Cells resuspended in assay buffer (1 tray to 10 ml).

Harvesting Cells

Supernatant is removed from cells. PBS (approximately 20 ml) is added. The cells are scraped and placed in a 50 ml centrifuge tube. The procedure is repeated with a further 10 ml of PBS to ensure that most of the cells are removed. The cells are pelleted by centrifuging for 20 min at 3000 rpm in a benchtop centrifuge, and then frozen if desired. The pellets are resuspended in 10 ml of buffer per tray (25 cm x 25 cm) of cells.

Assay

Can be carried out in deep 96-well plates or in tubes. Each tube contains:

• 300 μl of assay buffer.

• 50 μl of [³H]-flumazenil (final concentration for αlβ3γ2: 1.8 nM; for α2β3γ2: 1.8 nM; for α3β3γ2: 1.0 nM).

• 50 μl of buffer or solvent carrier (e.g. 10% DMSO) if compounds are dissolved in 10% DMSO (total); test compound or flunitrazepam (to determine non-specific binding), 10 μM final concentration.

• 100 μl of cells. Assays are incubated for 1 hour at 40°C, then filtered using either a

Tomtec or Brandel cell harvester onto GF/B filters followed by 3 x 3 ml washes with ice cold assay buffer. Filters are dried and counted by liquid scintillation counting. Expected values for total binding are 3000-4000 dpm for total counts and less than 200 dpm for non-specific binding if using liquid scintillation counting, or 1500-2000 dpm for total counts and less than 200 dpm for non-specific binding if counting with meltilex solid scintillant. Binding parameters are determined by non-linear least squares regression analysis, from which the inhibition constant Ki can be calculated for each test compound.

The compounds of the accompanying Examples were tested in the above assay, and all were found to possess a Ki value for displacement of [³H]-flumazenil from the α2 and/or α3 subunit of the human GABA_A receptor of 100 nM or less.

INTERMEDIATE 1

(4-Chlorothiazol-2-yl)acetic acid ethyl ester

a) 2.4-Dichlorothiazole

A mixture of thiazolidine-2,4-dione (25.0 g, 0.21 mmol), pyridine (16.1 g, 0.20 mol) and phosphorus oxychloride (227 g, 1.48 mol) were heated under reflux for 18 h. The phosphorus oxychloride was removed by distillation and the residue poured onto ice/water (600 ml). The aqueous phase was extracted with ethyl acetate (4 x 200 ml). The combined organics were washed with IN sodium hydroxide and brine, dried (Na S0₄), filtered and evaporated to give the title-product as a light brown solid, ⁱH NMR (CDC1₃) δ 7.01 (1H, s).

b) 2-(4-Chlorothiazol-2-yl)malonic acid diethyl ester

Sodium hydride (60% dispersion in oil, 5.19 g, 0.13 mol) was added portionwise over 20 min to a 0°C solution of diethyl malonate (20.8 g, 0.13 mol) in tetrahydrofuran (250 ml). The mixture was allowed to warm to room temperature over 45 min, 2,4-dichlorothiazole was added and the mixture heated under reflux for 18 h. The solvent was evaporated and the residue made acidic by addition of IN citric acid solution. The aqueous phase was extracted 3 times with diethyl ether. The combined organic layers were washed with brine, dried (MgS0₄), filtered and pre-adsorbed onto silica gel. The product was purified by chromatography on silica gel, eluting with isohexane/ethyl acetate, to give the title-product as a pale yellow oil, Η NMR (CDC1₃) δ 1.28 (6H, t, J 7 Hz), 4.24 (4H, q, J 7 Hz), 5.14 (1H, s), 7.17 (1H, s).

c) (4-Chlorothiazol-2-yl)acetic acid ethyl ester

A mixture of the preceding ester (17.9 g, 65 mmol), sodium chloride (7.6 g, 129 mmol) and water (2.3 g, 129 mmol) in dimethylsulfoxide (90 ml) was heated at reflux for 1.5 h. After cooling to room temperature, the reaction was quenched by the addition of water then extracted with diethyl ether. The organic layer was washed with brine (150 ml), dried (MgS0₄), filtered and evaporated to give a brown oil. Purification by silica gel chromatography, eluting with isohexane/ethyl acetate, gave the title- product as an orange oil, Η NMR (CDCI3) δ 1.29 (3H, t, J 7 Hz), 4.03 (2H, s), 4.22 (2H, q, J 7 Hz), 7.08 (1H, s).

INTERMEDIATE 2

(4-Cyclopropylthiazol-2-yl)acetic acid ethyl ester A cooled (-10°C) solution of cyclopropyl methyl ketone (10.3 g, 122 mmol) in ethanol (150 ml) was treated with bromine (22.5 g, 141 mmol) added dropwise over 10 min. The resulting orange solution was stirred to ambient temperature over 2 h giving a colourless solution. This was treated with a solution of thiocarbamoylacetic acid ethyl ester [prepared according to the procedure of Gauthier et al. in Phosphorus, Sulfur,

Silicon, Relat. Elem., 1994, 95 & 96 (1-4), pp. 325-6] (18 g, 122 mmol) in ethanol (75 ml) and this mixture heated at 60°C for 3 h. The reaction was cooled to ambient temperature then evaporated. The resulting residue was suspended in water (250 ml) then made basic by the cautious addition of solid sodium hydrogencarbonate. The aqueous was extracted twice with ether, the combined organics were washed with brine, dried (Na₂S0₄), filtered and pre-adsorbed onto silica gel. Purification by dry flash chromatography on silica gel, eluting with isohexane/ether, gave the title- compound as a pale yellow liquid which crystallised on standing, ¹H NMR (CDCls) δ 0.80-0.95 (4H, m), 1.27 (3H, t, J 7 Hz), 1.99-2.08 (1H, m), 4.00 (2H, s), 4.22 (2H, q, J 7 Hz), 6.79 (1H, s).

EXAMPLE 1

10-(2.4-Dichlorophenyl)-8-(4-methylthiazol-2-yl)-5.6-dihvdro-4H-2.3a,6a- triaza-benzo \e] azulen-7-one

a) iy^"-(3-Hydroxypropyl)-2-(4-methylthiazol-2-yl)acetamide

To a solution of (4-methylthiazol-2-yl)acetic acid ethyl ester (2.5 g, 14.8 mmol) in methanol (5 ml) was added 3-aminopropanol (1.8 ml, 24 mmol). The solution was stirred overnight at room temperature. The solvent was evaporated and the residue partitioned between water and dichloromethane. The aqueous layer was extracted seven times with dichloromethane (the first two extractions were discarded as they contained mainly impurities). The combined organics were dried (Na Sθ4) and the solvent evaporated to give the title-αZco/toZ as a beige solid, *H NMR (CDCI3) δ 1.65-1.75 (2H, m), 2.44 (3H, s), 3.62 (2H, t, J 5.5 Hz), 3.42-3.49 (2H, m), 3.91 (2H, s), 6.83 (1H, s), 7.40 (1H, br s).

b) l-( lH-Imidazol-4-yl)-2-nitroethanone To a suspension of imidazole-4-carboxylic acid (10 g, 89 mmol) in dry iV,iv^"-dimethylformamide (150 ml) under nitrogen was added dropwise N,N'- carbonyldiimidazole (18 g, 111 mmol). The mixture was stirred for 2.5 h at 70°C then cooled down to room temperature before adding nitromethane (29 ml, 535 mmol). The solution was further cooled down to 0°C and sodium hydride (11 g, 275 mmol) was added slowly. The pink mixture was heated at 60°C for 8 h and then stirred at room temperature overnight. The mixture was cooled down to 0°C and 10% aqueous citric acid was added carefully. The solid was filtered, washed with water then ether and dried (P₂0₅) to give the title-imidazole, VB. NMR (d₆-DMSO) δ 6.15 (2H, s), 7.91 (1H, s), 7.95 (1H, s), 13.05 (1H, br s).

c) l-(3-Hydroxypropyl)-3-(4-methylthiazol-2-yl)-5-nitro-6-(l-trityl-lH- imidazol-4-yl)- lH-pyridin-2-one

To a suspension of the preceding imidazole (1.05 g, 6.77 mmol) in acetonitrile (10 ml) was added iV,iV-dimethylformamide dimethyl acetal (5 ml, 40.6 mmol). The mixture was stirred for 2 h at room temperature and for 30 min at 40°C. The volatiles were evaporated and the residue dissolved in A^AT-dimethylformamide (10 ml). Trityl chloride (2 g, 7.55 mmol) was added followed by sodium hydride (300 mg, 7.5 mmol) and the mixture stirred for 45 min at room temperature. The alcohol from step a) (1 g, 4.7 mmol) was added followed by methanol (0.58 ml, 14.8 mmol) and sodium hydride (600 mg, 15 mmol). The red mixture was stirred for 2 h at room temperature then water was added and the mixture extracted 3 times with ethyl acetate. The combined organics were washed with brine, dried (Na₂S0₄) and the solvent evaporated. The residue was purified by column chromatography on silica gel, using dichloromethane/methanol as eluent, to give the title-product as a yellow foam, Η NMR (CDCls) δ 1.90-2.00 (2Η, m), 2.53 (3H, s), 3.51-3.58 (2H, m), 4.29 (2H, t, J 6.5 Hz), 6.98 (1H, s), 7.07 (1H, s), 7.12-7.20 (6H, m), 7.31-7.40 (10H, m), 7.72 (1H, s), 9.09 (1H, s). d) 8-(4-Methylthiazol-2-yl)-10-nitro-5,6-dihvdro-4H-2.3a.6a-triaza- benzo \e\ azulen-7-one

To a solution of the foregoing alcohol (1.8 g, 2.98 mmol) in dichloromethane (5 ml) was added thionyl chloride (3 ml). The solution was stirred for 2 h at room temperature, evaporated and azeotroped with toluene. The residue was dissolved in formic acid (15 ml) and the solution stirred for 6 days at room temperature. Ether was added and the organic layer was extracted 4 times with water. The combined aqueous extracts were basified with sodium hydroxide and extracted twice with dichloromethane. The combined organics were dried (Na₂Sθ4), evaporated and purified by column chromatography on silica gel, using dichloromethane/methanol as eluent, to give a mixture of chloro and cyclised material (480 mg). The mixture was dissolved in acetonitrile (10 ml) and sodium hydride (10 mg, 2.54 mmol) was added. The reaction mixture was stirred at 40°C for 1.5 h then cooled down to 0°C and quenched with water. The aqueous was extracted with dichloromethane and the combined organics dried (Na₂S04) and evaporated. The residue was dissolved in dichloromethane and the solid filtered off. The dichloromethane was evaporated and the residue triturated with methanol to give the title-compound as an orange solid, Η NMR (dβ-DMSO) δ 2.20- 2.30 (2Η, m), 2.47 (3H, s), 2.25-2.35 (2H, lump), 7.46 (IH, s), 7.61 (IH, s),

8.04 (IH, s), 8.93 (IH, s).

e) 10-Amino-8-(4-methylthiazol-2-yl)-5,6-dihydro-4H-2,3a.6a-triaza- benzo Tel azulen-7-one

The foregoing nitro compound (130 mg, 0.38 mmol) was hydrogenated using palladium on carbon (30 mg) under an atmospheric pressure of hydrogen for 4 h. The catalyst was removed and the solvent evaporated to give the Hue-product, Η NMR (dβ-DMSO) δ 2.11-2.23 (2Η, m), 2.43 (3H, s), 4.09 (4H, br lump), 4.74 (2H, br lump), 7.28 (IH, d, J 2.5 Hz), 7.44 (IH, d, J

2.5 Hz), 7.89 (IH, s), 8.37 (IH, s); MS, CI⁺ m/z = 314 for (M+H)+. f) 10-Iodo-8-(4-methylthiazol-2-yl)-5.6-dihvdro-4H-2,3a.6a-triaza- benzo \e] azulen-7-one

To a solution of the preceding amine (40 mg, 0.127 mmol) in a 1/1 mixture of concentrated hydrochloric acid and water (2 ml) at 0°C was added cold sodium nitrite (13 mg, 0.188 mmol) in water (1 ml). After 30 min at 0°C the yellow diazonium solution was added slowly to a solution of potassium iodide (150 mg, 0.9 mmol) in water (1 ml) at 0°C. After 10 min the reaction was diluted with water and basified with 4N aqueous sodium hydroxide. The aqueous was extracted twice with dichloromethane and the combined organics were dried (Na₂S04) and the solvent evaporated. The residue was purified by column chromatography on silica gel, using dichloromethane/methanol as eluent, to give the title-product, Η NMR (dβ- DMSO) δ 2.10-2.22 (2H, ), 2.43 (3H, s), 3.05 (IH, br lump), 3.86 (IH, br lump), 4.45 (IH, br lump), 5.00 (IH, br lump), 7.34 (IH, d, J 2.5 Hz), 7.62 (IH, s), 7.91 (IH, s), 8.74 (IH, s). MS, CI⁺ mlz = 425 for (M+H)⁺.

g) 10-(2.4-Dichlorophenyl)-8-(4-methylthiazol-2-yl)-5.6-dihvdro-4H-2.3a.6a- triazabenzo fβl azulen-7-one To a solution of the preceding iodide (50 mg, 0.118 mmol) in N,N- dimethylformamide (5 ml) was added 2,4-dichlorophenylboronic acid (50 mg, 0.236 mmol) followed by potassium phosphate (23 mg, 0.118 mmol). The mixture was deoxygenated for 45 min before adding tetrakis(triphenylphosphine)palladium(0) (100 mg, 0.08 mmol). The mixture was heated at reflux for 3 h and cooled down to room temperature before adding a solution of 10% aqueous sodium carbonate. The mixture was extracted twice with ethyl acetate and the combined organics were washed 3 times with water, dried (Na₂S04) and evaporated. The residue was purified by ion exchange column chromatography using SCX cartridges eluting with 10% ammonia in methanol to give the title-compound, *H NMR (dβ-DMSO) δ 2.27-2.37 (2H, m), 2.42 (3H, s), 4.07 (2H, br lump), 4.42 (2H, br lump), 6.42 (IH, s), 7.37 (IH, s), 7.52 (IH, br lump), 7.27 (IH, s), 7.87 (IH, s), 8.31 (IH, s). MS, CI+ m/z = 443 and 445 for (M+H)+.

Examples 2 to 21 were prepared following the procedure described for Example 1 using the appropriate boronic acid in step g).

Examples 22 to 31 were prepared following the procedure described for Example 1 using the appropriate ester in step a) and phenylboronic acid in step g).

EXAMPLE 32

10-Benzylamino-8-(4-methylthiazol-2-yl)-5.6-dihydro-4H-2,3a,6a-triaza- benzo \e\ azulen-7-one To a solution of the amine from Example 1 step e) (30 mg, 0.09 mmol) in methanol (7 ml) was added benzaldehyde (0.01 ml, 0.09 mmol) followed by acetic acid (0.05 ml). The solution was stirred for 15 min at room temperature before adding sodium cyanoborohydride (7 mg, 0.11 mmol). The reaction was stirred overnight at room temperature, quenched with water and evaporated. The residue was partitioned between 10% aqueous potassium carbonate and dichloromethane, the aqueous was separated and re-extracted with dichloromethane and the combined organics dried (Na₂S0₄) and evaporated. The residue was purified by column chromatography on silica gel, using dichloromethane/methanol as eluent, to give the title-compound, Η NMR (dβ-DMSO) δ 2.11-2.22 (2H, m), 2.41 (3H, s), 4.00 (4H, br lump), 4.39 (2H, d, J 6 Hz), 5.16 (IH, t, J 6 Hz), 7.15-7.33 (5H, m), 7.49 (IH, s), 7.94 (IH, s), 8.27 (IH, s). MS, CI+ m/z = 404 for (M+H)+. EXAMPLE 33

10-(i\ -Benzyl-A -methylamino)-8-(4-methylthiazol-2-yl)-5.6-dihvdro-4H- 2.3a,6a-triazabenzo \e\ azulen-7-one To a solution of the preceding amine (20 mg, 0.05 mmol) in methanol

(7 ml) was added formaldehyde (0.015 ml, 0.05 mmol) followed by acetic acid (0.04 ml). The solution was stirred for 15 min at room temperature before adding sodium cyanoborohydride (4 mg, 0.6 mmol). The reaction was stirred overnight at room temperature, quenched with water and evaporated. The residue was partitioned between 10% aqueous potassium carbonate and dichloromethane and the aqueous was separated and re- extracted with dichloromethane. The combined organic layers were dried (Na₂S0₄) and evaporated. The residue was purified by column chromatography on silica gel, using dichloromethane/methanol as eluent, to give the title-compound, *H NMR (CDC1₃) δ 2.12-2.25 (2H, m), 2.57 (3H, d, J 2.5 Hz), 2.84 (3H, s), 3.40 (4H, br lump), 3.90 (2H, s), 6.85 (2H, dd, 2 and 7 Hz), 7.00-7.14 (4H, m), 7.49 (IH, d, J 2 Hz), 7.51 (IH, s), 8.83 (IH, s). MS, CI⁺ m/z = 418 for (M+H)⁺.

Examples 34 to 36 were prepared following the procedure described for Example 32 using the appropriate aldehyde.

EXAMPLE 37

8-(4-Methylthiazol-2-v -7-oxo-5.6-dihvdro-4H.7H-2.3a.6a-triaza- benzofelazulene-10-carboxylic acid methyl ester

To a deoxygenated solution of the product from Example 1 step f) (290 mg, 0.68 mmol) in a 1/1 mixture of iV,iV-dimethylformamide and methanol

(30 ml) was added diisopropylethylamine (0.35 ml, 2.04 mmol) followed by l,3-bis(diphenylphosphino)propane (41 mg, 0.1 mmol) and palladium(II) acetate (22.4 mg, 0.1 mmol). After further deoxygenation, the mixture was cooled down to 0°C before bubbling carbon monoxide through for 15 min. The reaction was then heated to 75°C and stirred under a slow stream of carbon monoxide for 4 h. The reaction mixture was cooled down to room temperature and quenched with water. The aqueous was extracted twice with ethyl acetate and the combined organics dried (Na₂S0 ) and evaporated. The residue was purified by column chromatography on silica gel, using dichloromethane/methanol as eluent, to give the title-methyl ester, NMR (CDCls) δ 2.33-2.45 (2H, ), 2.54 (3H, d, J 2.5 Hz), 3.80 (3H, s), 4.15 (4H, br lump), 7.06 (IH, d, J 2 Hz), 7.54 (IH, d, J 2 Hz), 7.66 (IH, s), 8.97 (IH, s), MS, CI+ m/z = 357 for (M+H)⁺.

EXAMPLE 38

10-(4-Methoxyphenyl)-3-methyl-8-(4-methylthiazol-2-yl)-5.6-dihvdro-4H- 2.3a.6a-triazabenzo[elazulen-7-one

To the product of Example 2 (21 mg, 0.05 mmol) in tetrahydrofuran at -78°C under nitrogen was added n-butyllithium (0.04 ml of a 1.6M solution in hexanes) and the resulting mixture was stirred at -78°C for 35 min before adding a solution of methyl iodide in tetrahydrofuran (0.1 ml of a solution made from 0.2 ml of methyl iodide in 5 ml of tetrahydrofuran, 0.064 mmol). The mixture was stirred overnight at room temperature and then partitioned between water and ethyl acetate. The organic layer was separated, dried (MgSθ4) and evaporated. Preparative ΗPLC afforded the title-product, NMR (dβ-DMSO) δ 2.20-2.31 (2Η, m), 2.36 (3H, s), 2.41 (3H, s), 3.77 (3H, s), 4.13 (2H, br lump), 6.34 (IH, s), 6.91 (2H, dd, J 2 and 7 Hz), 7.15 (2H, dd, 2 and 7 Hz), 7.31 (IH, d, J 2 Hz), 8.34 (IH, s). MS, CI+ m/z = 419 for (M+H)+. EXAMPLE 39

10-Benzyloxy-8-(4-methylthiazol-2-yl)-5.6-dihydro-4H-1.3a.6a- triazabenzo [el azulen-7-one

a) l-r3-(fer^-Butyldiniethylsilanyloxy)propyl1--LH-imidazole

To imidazole (15.0 g, 0.22 mol) in dry dichloromethane (200 ml) was added 3-bromopropanol (10 ml), and the mixture stirred at 22°C for 3 h. To the resulting mixture was then added terέ-butyldimethylsilyl chloride (16.58 g), and the mixture stirred for a further 18 h. The solvent was evaporated and the residue re-dissolved in dry iv^N-dimethylformamide (100 ml). Anhydrous sodium carbonate (50 g) was added, and the mixture was heated at 100°C for 18 h. On cooling, the mixture was partitioned between dichloromethane and water. The organic layer was washed with water, dried (Na₂Sθ4), and evaporated. The residue was chromatographed on silica gel, eluting with 6% methanol in dichloromethane, to afford the title- product as a colourless oil, MS, CI+ m/z = 241 for (M+Η)⁺.

b) 2-Benzyloxy-l-{l-f3-(fer^-butyldimethylsilanyloxy)propyll-lH-imidazol- 2-yljethanone

To the foregoing imidazole (6.0 g, 25 mmol) in dry tetrahydrofuran (100 ml), under nitrogen at -78°C, was added n-butyllithium (17.5 ml, 1.6 M). After stirring for 0.5 h at -78°C, 2-benzyloxy-iV-methoxy-iV- methylacetamide (5.58 g) was added via syringe. After stirring for 1 h at -78°C and at room temperature for 1 h, the mixture was quenched by addition of aqueous citric acid. The pH of the mixture was then adjusted to pH 10 by addition of aqueous sodium hydroxide, and the product extracted with ethyl acetate. The organic extract was evaporated and the residue chromatographed on silica gel, eluting with dichloromethane, to afford the title-product as a colourless oil, MS, CI+ m/z = 389 for (M+H)+. c) 5-Benzyloxy-6- [l-(3-hydroxypropyl)-lH-imidazol-2-yll -3-(4-methylthiazol- 2-yl)-lH-pyridin-2-one

To the previous ethanone (3.22 g) was added A iV-dimethylformamide dimethyl acetal (40 ml), and potassium terέ-butoxide (0.02 g). The resulting solution was heated at reflux for 22 h. The solvent was evaporated, and the residue azeotroped with toluene to afford a yellow oil. Dry N,N- dimethylformamide (20 ml) and (4-methylthiazol-2-yl)acetamide (1.295 g) were added, followed by sodium methoxide (0.8 ml of a 0.5 M solution in methanol). To the resulting mixture, stirred under nitrogen at 0°C, was added sodium hydride (0.692 g of a 60% dispersion in oil). The resulting mixture was stirred at room temperature for 4 days, then quenched by addition of aqueous NH4CI. The mixture was partitioned between water and dichloromethane. The organic layer was separated, evaporated, and the residue chromatographed on silica gel, eluting with 7% methanol in dichloromethane, to afford the title-product as a yellow solid, MS, CI+ m/z = 423 for (M+H)⁺.

d) 10-Benzyloxy-8-(4-methylthiazol-2-yl)-5.6-dihydro-4H-l,3a,6a- triazabenzo [el azulen-7-one To the previous pyridinone (1.775 g) in dry dichloromethane (50 ml) was added triphenylphosphine (1.216 g), followed by diethyl azodicarboxylate (0.78 ml), dropwise, with stirring. The mixture was then stirred at room temperature for 16 h. The solvent was evaporated in vacuo and the residue chromatographed on silica gel, eluting with 5% methanol in dichloromethane. The product was recrystallised from warm ethyl acetate on dilution with diethyl ether, *H NMR (CDCI3) δ 2.27 (2H, m), 2.56 (3H, s), 3.63 (2H, broad s), 5.15 (2H, broad s), 6.99 (IH, s), 7.06 (IH, s), 7.14-7.29 (6H, m), 8.72 (IH, s); MS, CI+ m/z = 405 for (M+H)⁺. EXAMPLE 40

10-Benzyloxy-8-(4-methylthiazol-2-yl)-5.6-dihydro-4H-1.3.3a.6a- tetraazabenzo [el azulen-7-one

a) l-[3-(ter^-Butyldimethylsilanyloxy)propyll-lH^'-[1.2,41triazole

To [1,2,4] -triazole (7.53 g, 0.109 mol) in dry iV,iV-dimethylformamide (100 ml) under nitrogen at 4°C was added, with stirring, portionwise, sodium hydride (4.40 g of a 60% dispersion in oil). After stirring for 0.25 h, 3-bromopropanol (10 ml) was added dropwise. The mixture was stirred at room temperature for 1 h, recooled to 4°C, and then ferέ-butyldimethylsilyl chloride (16.59 g) and dry triethylamine (17 ml) added. The cooling bath was removed and the mixture stirred for 5 h at room temperature. The mixture was partitioned between dichloromethane and water and the organic layer was separated, washed with water, dried (Na₂S04), and evaporated. The residue was used without further purification, ^XΗ NMR (CDC1₃) δ 0.02 (6H, s), 0.86 (9H, s), 2.02 (2H, m), 3.52 (2H, t, J 6.5 Hz), 4.26 (2H, t, J 7 Hz), 7.89 (IH, s), 8.01 (IH, s).

b) 2-Benzyloxy-l-{2- [3-(fer£-butyldimethylsilanyloxy)propyH -2H-

[l,2,4]triazol-3-yl)ethanone

The foregoing triazole was reacted according to the procedure described in Example 39 step b). The product was chromatographed on silica gel, eluting with 2.5% methanol in dichloromethane, to afford the title-product as an oil, *H NMR (CDCI3) δ 0.01 (6H, s), 0.86 (9H, s), 2.03 (2H, m), 3.64 (2H, t, J 6 Hz), 4.66 (4H, m), 4.88 (2H, s), 7.28-7.36 (5H, m), 7.86

(IH, s). MS, CI⁺ m/z = 390 for (M+H)+. c) 5-Benzyloxy-6-[2-(3-hvdroxypropyl)-2H-fl.2.41triazol-3-yll-3-(4- methylthiazol-2-yl)-lH-pyridin-2-one

To the previous ethanone (6.60 g) was added iV^",iV-dimethylformamide dimethyl acetal (40 ml), and the resulting solution aged at room temperature for 18 h. The solvent was then evaporated and the residue azeotroped with toluene to afford a yellow oil. Dry iV,iV-dimethylformamide (40 ml) and (4-methylthiazol-2-yl)acetamide (2.64 g) were added, followed by sodium methoxide (0.8 ml of 0.5 M solution in methanol). To the resulting mixture, stirred under nitrogen at 0°C, was added sodium hydride (1.4 g of a 60% dispersion in oil). The resulting mixture was stirred at room temperature for 18 h, then quenched by addition of aqueous hydrochloric acid to pH 1, and the mixture allowed to stand for 0.5 h. The mixture was diluted with water, the pH adjusted to pH 8 by addition of 4N aqueous sodium hydroxide and the mixture extracted with 10% methanol in dichloromethane. The organic layer was separated, evaporated, and the residue chromatographed on silica gel, elutig with 5% to 10% methanol in dichloromethane, to afford the title-product, which was recrystallised from hot toluene, MS, CI+ m/z = 424 for (M+H)+.

d) 10-Benzyloxy-8-(4-methylthiazol-2-yl)-5.6-dihvdro-4H-1.3.3a.6a- tetraazabenzo [e] azulen-7-one

To the foregoing pyridinone (2.06 g) in dry tetrahydrofuran (60 ml) was added triphenylphosphine (1.40 g), followed by diethyl azodicarboxylate (0.90 ml), dropwise with stirring, at 15°C. The mixture was then stirred at room temperature for 8 h, the solvent evaporated and the residue chromatographed on silica gel, eluting with 5% methanol in dichloromethane. The product was recrystallised from warm ethyl acetate on dilution with isohexane, Η NMR (dβ-DMSO) δ 2.28-2.34 (2Η, m), 2.47 (3H, d, J 1 Hz), 3.99 (2H, s), 4.28 (2H, t, J 7 Hz), 5.18 (2H, s), 7.26-7.43 (6H, m), 8.24 (IH, s), 8.57 (IH, s); ¹³C NMR (100 MHz, dβ-DMSO) 17.46, 28.76, 43.28, 45.06, 74.64, 118.52, 124.28, 127.23, 128.36, 128.38, 128.60, 129.37, 136.87, 140.71, 145.60, 151.38, 152.67, 157.28, 158.89; MS, CI+ m/z = 406 for (M+H)+.

EXAMPLE 41

8-(4-Methylthiazol-2-yl)-10-phenyl-5.6-dihvdro-4H-1.3.3a.6a- tetraazabenzo [e] azulen-7-one

a) 10-Hydroxy-8-(4-methylthiazol-2-yl)-5.6-dihydro-4H-1.3.3a.6a-tetraaza- benzo [el azulen-7-one

To the product of Example 40 (0.95 g, 2.34 mmol) in dry dichloromethane (5 ml), cooled at 4°C under nitrogen, was added with stirring a 1.0 M solution of boron tribromide in dichloromethane (10 ml). The cooling bath was removed and the mixture stirred at room temperature for 1.5 h. The mixture was then cooled to 4°C and quenched by dropwise addition of methanol (5 ml). The reaction was then diluted with diethyl ether (100 ml), and water (100 ml). The organic phase was separated, washed with water, and the combined aqueous phases concentrated at reduced pressure to a volume of 50 ml. 4N Sodium hydroxide (6 ml) was added and the pH then adjusted to pH 4 by addition of acetic acid (1 ml). The product was extracted with n-butanol and the combined extracts were evaporated. The residue was chromatographed on silica gel, eluting with 5% methanol in dichloromethane, to give the title-product.

b) Trifluoromethanesulfonic acid 8-(4-methylthiazol-2-yl)-7-oxo-5.6- dihvdro-4H.7H-l,3,3a,6a-tetraazabenzo[e1azulen-10-yl ester To the preceding alcohol (0.127 g, 0.313 mmol) in dry dichloromethane (8 ml) was added 2,6-lutidine (0.06 ml). The mixture was cooled to -78°C under nitrogen and trifluoromethanesulfonic anhydride (0.110 ml) was added with stirring. After 1 h at -78°C, the cooling bath was removed and the mixture stirred at room temperature for 1 h. The mixture was then partitioned between dichloromethane and water. The organic layer was separated, washed with brine, evaporated, and the residue chromatographed on silica gel, eluting with 5% methanol in dichloromethane, to afford the title-compound, MS, CI+ m/z =448 for (M+H)+.

c) 8-(4-Methylthiazol-2-yl)-10-phenyl-5.6-dihvdro-4H-1.3.3a.6a- tetraazabenzo [e] azulen-7-one

To the preceding ester (0.041 g) and phenylboronic acid (0.198 g) in dry iV,iV^"-dimethylformamide (18 ml) was added potassium phosphate (0.278 g) and tetrakis(triphenylphosphine)palladium(0). The mixture was deoxygenated under nitrogen and then heated at 100°C for 18 h. The mixture was then partitioned between ethyl acetate and water. The organic layer was separated, washed with water, evaporated, and the residue chromatographed on silica gel, eluting with 3.5% methanol in dichloromethane, to afford the title-compound, Η NMR (CDCla) δ 2.40 (2H, m), 2.47 (3H, s), 4.04 (2H, br s), 4.38 (2H, m), 6.99-7.04 (3H, m), 7.15-7.18 (3H, m), 7.68 (IH, s), 9.03 (IH, broad s). MS, CI+ m/z = 376 for (M+H)⁺.

EXAMPLE 42

10-Benzyloxy-8-(4-methylthiazol-2-yl)-5.6-dihvdro-4H-1.2.3a.6a-tetraaza- benzo \e\ azulen-7-one

Prepared using the procedure described for Example 39 steps b) to d) using 4-[3-( er£-butyldimethylsilanyloxy)propyl]-4H-[l,2,4]triazole instead of l-[3-( er£-butyldimethylsilanyloxy)propyl]-lH-irrndazole.

EXAMPLE 43

10-Cvclobutoxy-8-(4-methylthiazol-2-yl)-5.6-dihvdro-4H-1.2.3a.6a- tetraazabenzo [e] azulen-7-one a) 10-Hydroxy-8-(4-methylthiazol-2-yl)-5.6-dihydro-4H-l,2,3a.6a-tetraaza- benzo fβl azulen-7-one

The title-compound was obtained following the procedure described for Example 41 step a) using the product of Example 42 instead of the product from Example 40.

b) 10-Cvclobutoxy-8-(4-methylthiazol-2-yl)-5.6-dihvdro-4H-1.2.3a.6a- tetraazabenzo \e\ azulen-7-one To the foregoing alcohol (0.283 g) and triphenylphosphine (1.068 g) in dry dichloromethane (4 ml) was added cyclobutanol (0.30 ml), followed by diethyl azodicarboxylate (0.670 g), dropwise with stirring. The mixture was stirred for 18 h at room temperature, then the solvent was evaporated at reduced pressure and the residue subjected to chromatography on silica gel, eluting with 5% methanol in dichloromethane. The product was crystallised from warm dichloromethane, diethyl ether and isohexane by boiling, to afford the title-compound as a yellow solid, Η NMR (CDCls) δ 0.35 (2H, m), 0.56 (2H, m), 1.27 (IH, m), 2.41 (2H, m), 2.55 (3H, s), 4.05-4.30 (6H, m), 7.10 (IH, m), 8.30 (IH, s), 8.63 (IH, s). MS, CI+ m/z = 370 for (M+H)+.

Examples 44 to 47 were prepared following the procedure described for Example 43 using the appropriate alcohol in step b).

EXAMPLE 48

8-(4-Methylthiazol-2-v -10-phenyl-5.6-dihvdro-4H-l,2,3a,6a-tetraaza- benzo \e\ azulen-7-one a) Trifluoromethanesulfonic acid 8-(4-methylthiazol-2-yl)-7-oxo-5.6- dihydro-4H,7H-l,2.3a,6a-tetraazabenzo [elazulen-10-yl ester

The title-com-_jpoz ct^" was obtained following the procedure described for Example 41 step b) using the product of Example 43 step a).

b) 8-(4-Methylthiazol-2-yl)-10-phenyl-5.6-dihvdro-4H-1.2.3a.6a-tetraaza- benzo [e] azulen-7-one

To a solution of the previous triflate (22 mg, 0.05 mmol) in N,N- dimethylformamide (2 ml) was added phenylboronic acid (15 mg, 0.07 mmol) followed by potassium phosphate (12 mg, 0.06 mmol). The mixture was deoxygenated with nitrogen for 45 min before adding tetrakis(triphenylphosphine)palladium(0) (25 mg, 0.02 mmol). The mixture was heated overnight at 100°C and evaporated. The residue was purified by ion exchange chromatography using SCX cartridges eluting with 10% ammonia in methanol to give the title-compound, which was further purified by mass lynx to yield the trifluoroacetic acid salt, *Η NMR (dβ- DMSO) δ 2.25-2.33 (2H, m), 2.44 (3H, d, J 2.5 Hz), 4.00 (2H, br lump), 4.40 (2H, br lump), 7.18-7.22 (2H, m), 7.29-7.37 (3H, m), 7.42 (IH, s), 8.47 (IH, s), 8.72 (IH, s); MS, CI+ m/z = 376 for (M+H)⁺.

Examples 49 to 52 were prepared following the procedure described for Example 48 using the appropriate boronic acid in step b).

Example 16

Example 17

Example 18

Example 19

Example 20

Example 21

Example 22

Example 23

Example 24

Example 25

Example 26

Example 27

Example 28

Example 29

Example 30

Example 31

Example 32

Example 33

Example 34

Example 35

Example 36

Example 37

Example 38

Example 39

Example 40

Example 41

Example 42

Example 43

Example 44

Example 45

Example 46

Example 47

Example 48

Example 49

Example 50

Example 51

Example 52

Claims

CLAIMS;

1. A compound of formula (I), or a salt or N-oxide thereof:

(I)

wherein

E represents -(CH₂)_n-; n is 1, 2 or 3; Q represents the residue of an imidazole or triazole ring;

R¹ and R² independently represent hydrogen, hydrocarbon, a heterocyclic group, halogen, cyano, trifluoromethyl, nitro, -OR^a, -OCOR^a, -OS0₂R^a, -SR^a, -SOR^a, -S0₂R^a, -S0₂NR^aR^b, -NR^aR^b, -NR^aCOR^b, -NR^aC0₂R^b, -COR^a, -C0₂R^a or -CONR^aR^b; R³ represents hydrogen or Cι-β alkyl; and

R^a and R^b independently represent hydrogen, hydrocarbon or a heterocyclic group; the hydrocarbon and heterocyclic groups represented by R¹, R², R³, R^a and R^b being optionally substituted by one or more groups selected from Ci-β alkyl, C3-7 cycloalkyl, adamantyl, phenyl, benzyl, halogen, Ci-β haloalkyl, Cι-β hydroxyalkyl, Cι-β aminoalkyl, trifluoromethyl, hydroxy, Ci-β alkoxy, aryloxy, keto, Cι-3 alkylenedioxy, nitro, cyano, carboxy, C₂-β alkoxycarbonyl, C₂-β alkoxycarbonyl(Cι-β)alkyl, C_2-β alkylcarbonyloxy, arylcarbonyloxy, aminocarbonyloxy, formyl, C₂-β alkylcarbonyl, arylcarbonyl, Ci-β alkylthio, Cι-β alkylsulphinyl, Ci-β alkylsulphonyl, arylsulphonyl, -NR^VR^W, -NR^vCOR^w, -NR^vC0₂R^w, -NR^vS0₂Rw, - -CH₂NR^vS0₂R^w, -NHCONR^vR^w, -CONR^vR^w, -S0₂NR^vR^w and -CH₂S0₂NR^vR^w, in which R^v and R^w independently represent hydrogen, Ci-β alkyl, aryl or aryl(Cι-6)alkyl.

2. A compound according to claim 1 of formula (IA), (IB), (IC) or

(ID), or a salt or N-oxide thereof:

n°

wherein E, R¹, R² and R³ are as defined in claim 1.

3. A compound according to claim 1 of formula (II), or a salt or N-oxide thereof:

(II)

wherein X represents oxygen or sulphur;

Y and Z independently represent CH or nitrogen;

R¹¹ represents hydrogen, Ci-β alkyl, C3-7 cycloalkyl or halogen; and

Q, R² and R³ are as defined in claim 1.

4. A compound according to claim 3 wherein Y and Z are both

CH.

5. A compound according to claim 3 wherein X is sulphur, Z is nitrogen and Y is CH or nitrogen.

6. A pharmaceutical composition comprising a compound according to any of claims 1-5 in association with a pharmaceutically acceptable carrier.

7. A compound according to any of claims 1-5 for use in therapy.

8. The use a compound according to any of claims 1-5 in the manufacture of a medicament for treatment or prevention of anxiety.

9. The use of a compound according to any of claims 1-5 in the manufacture of a medicament for treatment or prevention of convulsions.

10. A method for the treatment or prevention of anxiety which comprises administering to a patient in need of such treatment an effective amount of a compound according to any of claims 1-5.

11. A method for the treatment or prevention of convulsions which comprises administering to a patient in need of such treatment an effective amount of a compound according to any of claims 1-5.

12. A process for the preparation of a compound of formula (I) as defined in claim 1 which comprises cyclising a compound of formula (III):

(Ill)

wherein E, Q, R¹, R² and R³ are as defined in claim 1, and L¹ represents a readily displaceable group.

13. A process for the preparation of a compound of formula (I) as defined in claim 1 which comprises cyclising a compound of formula (TV):

⁽IV⁾ wherein E, Q, R¹, R² and R³ are as defined in claim 1 and L² represents a readily displaceable group.