GB2136799A

GB2136799A - Quinoline derivatives

Info

Publication number: GB2136799A
Application number: GB08401333A
Authority: GB
Inventors: Roger Crossley; Kenneth Heatherington
Original assignee: John Wyeth and Brother Ltd
Current assignee: John Wyeth and Brother Ltd
Priority date: 1983-01-19
Filing date: 1984-01-18
Publication date: 1984-09-26
Also published as: GB8401333D0; GB2136799B

Abstract

A process for preparing dihydro compounds of formula I, by rearranging compounds of formula II, e.g. in the presence of acids or noble metal catalysts, is described. The compounds II may be prepared from intermediates of formula III. <IMAGE> In these formulae R<1>, R<2>, R<3>, R<4>, R<5>, R<6> and R<7> are the same or different and represent hydrogen, or alkyl, cycloalkyl, aralkyl, or aryl radicals any of which radicals may be substituted, or R<1> and R<2> taken together or R<2> and R<3> taken together, form a 5, 6 or 7 membered ring which may be saturated or unsaturated and substituted or unsubstituted, R<4> and R<5> may also represent alkoxy, or cycloalkoxy, n is 1, 2 or 3 and, if more than one R<4> radical is present the R<4> radicals may be the same or different and R<6> and R<7> represent hydrogen, alkyl, cycloalkyl, or aralkyl radicals. Most of the compounds I, II and III are novel and are claimed. They are intermediates for anti-ulcer agents.

Description

SPECIFICATION Quinoline derivatives The invention relates to quinoline derivatives and especially to 5,6-dihydroquinolines and related compounds, to novel processes for preparing them and to novel compounds obtained by such processes.

In one aspect the invention provides a process for preparing dihydro compounds of formula I

and acid addition salts thereof, wherein R', R2, R3, R4, R5, R6 and R7 are the same or different and represent hydrogen, or alkyl, cycloalkyl, aralkyl, or aryl radicals any of which radicals may be substituted, or R1 and R2 taken together or R2 and R3 taken together, form a 5, 6 or 7 membered ring which may be saturated or unsaturated and substituted or unsubstituted, R4 and R5 may also represent alkoxy, or cycloalkoxy, n is 1,2 or 3 and, if more than one R4 radical is present the R4 radicals may be the same or different and R6 and R7 represent hydrogen, alkyl, cycloalkyl, or araikyl radicals, which process comprises re-arranging a compound of formula II

wherein R1, R2, R3, R4, R5, R6, R7 and n are as defined above.

The re-arrangement of compound II to compound I may be carried out under acidic or basic conditions.

Examples of acid catalysts which may be used are organic acids such as carboxylic acids e.g. lower alkylcarboxylic acids such as acetic acid, inorganic acids such as phosphoric acid, or polyphosphoric acid, Lewis acids e.g. boron trifluoride, zinc chloride or acid anhydrides e.g. acetic anhydride. Alternatively a noble metal catalyst, e.g. a Pt or Pd catalyst may be used, optionally in the presence of a weak base such as sodium acetate or a heterogeneous or homogeneous catalyst, e.g. PdC12(PhCN)2, PhCl[(C6H5)3P]3Ru3(CO)12 or lrCl(CO)[(C6H5)3P]2.

Preferably the rearrangement is carried out in the presence of acetic acid, a noble metal catalyst in the presence of a base, or a Lewis acid.

The above mentioned acids may be used to prepare acid addition salts of compounds of formula I and other compounds of the invention.

When any of R1, R2, R3, R4, R5, Re or R7 is an alkyl radical it is preferred that this is a lower alkyl radical of 1 to 6 carbon atoms which may have a straight or branched chain e.g. methyl, ethyl, n-and iso-propyl and n-, s- and t-butyl. When R4 or R5 is an alkoxy radical it is preferred that the radical is lower alkoxy in which the alkyl portion has 1 to 6 carbon atoms and is as defined above, for an alkyl radical.

When any of R1, R2, R3, R4, Re, R6 or R7 is a cycloalkyl radical such radicals having from 4 to 6 carbon atoms are preferred i.e. cyclobutyl, cyclopentyl or cyclohexyl. If R4 or R5 istcycloalkoxy the cycloalkyl portion of this group may be as just described for a cycloalkyl group.

An aralkyl group may be an arylalkyl group in which the alkyl portion is as described herein for an alkyl group. Preferred aralkyl groups are those having from 7-12 carbon atoms.

When any of R1, R2, R3, R4 or Rye is an aryl group it is preferably phenyl or substituted phenyl (substituted by e.g. alkyl, alkoxy or trifluoromethyl). The aryl portion of an aralkyl group may be substituted as described for a phenyl group.

The invention includes novel compounds of formula I and their acid addition salts wherein R1, R2, R3, R4, Re, Re, R7 and n are as defined above, with the proviso that R6 and R7 are not both hydrogen when R1, R2, R3, R4 and R5 are all hydrogen.

Preferred compounds are those of formula IA

or an acid addition salt thereof, wherein R1 is lower alkyl and R6 and R7 are selected from hydrogen and lower alkyl. A particular example is 3,8-dimethyl-5,6-dihydroquinoline or an acid addition salt thereof.

Some starting materials of formula II are also novel and these are included in the invention. They are compounds of formula II and their acid addition salts wherein R1, R2, R3, R4, Re, Re, R7 and n are as defined above in connection with formula I with the provisos that (1 ) when R1, R2, R3, R4 and R5 are all hydrogen, R6 and R7 are not both hydrogen and (2) when R1 and R3 are both phenyl and when R1 is methyl and R4 is methyl then Re and R7 are not both methyl.

A preferred sub group of these compounds are those of formula IIA

or an acid addition salt thereof wherein R1 is lower alkyl and R6 and R7 are selected from hydrogen and lower alkyl. Examples are 5,6,7,8-tetrahydro-3-methyl-8-(2-propylidene) quinoline, 5,6,7,8-tetrahydro-3-methyl-8 (methylene) quinoline, and their acid addition salts.

The starting materials of formula II may be prepared by dehydration of the corresponding compounds of formula Ill

wherein R1, R2, R3, R4, Re, R6, R7 and n are as defined above.

The dehydration may be carried out with usual dehydrating agents e.g. polyphosphoric acid or with acetic anhydride, (in which case an intermediate acetylated derivative may be formed, from which acetic acid is eliminated to give the compound of formula II), Some compounds of formula Ill are also novel and are included in the invention. These are compounds of formula Ill and their acid addition salts and esters of carboxylic acids wherein R1, R2, R3, R4, R5 and n are as defined above in connection with formula I and R6 and R7 are other than hydrogen when R1, R2, R3, R4 and R5 are all hydrogen and R6 and R7 are not both methyl when R4 is methyl.

Preferred compounds of formula Ill are the sub group of formula IIIA

or an acid addition salt thereof wherein R1 is lower alkyl and R6 and R7 are selected from hydrogen, lower alkyl, cycloalkyl, or lower aralkyl radicals. Exampies are [8R*]-5,6,7,8-tetrahydro-8-([2S*]-2.(2-hydroxy-1.

phenyl)propyl)-3-methylquinoline, 5,6,7,8-tetrahydro-8-(2(2-hydroxy)propyl-3-methylquinoline and their acid addition salts.

The compounds of formula Ill may be prepared by treatment of a compound of formula IV

wherein R1, R2, R3, R4, Rye and n are as defined in connection with formula I, and M is hydrogen, an alkali metal (e.g. sodium, potassium or lithium) or MgHal, where Hal is chlorine, bromine or iodine, with a carbonyl compound of formula V

wherein Re and R7 are as defined in connection with formula I, with the proviso that when R6 and R7 are both hydrogen then M is hydrogen.

The present invention also provides a new process for preparing compounds of formula I wherein Re and R7 are hydrogen from compounds of formula IV.

It has been reported by Hahn and Epsztajn, Roczniki Chemie, 1964, 38,989 that treatment of Vla or Vlb

with polyphosphoric acid gives the corresponding methylene compounds Vlla and Vllb

exclusively with no corresponding methyl isomer being formed. We have surprisingly found that compounds offormula I wherein R6 and R7 are hydrogen, can be obtained by treatment of a compound of formula IV wherein M is hydrogen with formaldehyde (which may be in the form of paraformaldehyde) in the presence of an organic acid anhydride, e.g. acetic anhydride.It is believed that an intermediate compound of formula Ill wherein R6 and R7 are both hydrogen is formed initially, this dehydrates to give a compound of formula II wherein R6 and R7 are hydrogen and the compound of formula II rearranges to give a compound of formula I wherein R6 and R7 are hydrogen. Previously compounds of formula I were relatively inaccessible see Rosen and Weber J.Org. Chem. 1977,42,47-50 who obtained 8-methyl-5,6-dihydroquinoline by pyrolysis of 1 -methyl-1 (a-pyridinyl)-1 ,3-butadiene. However pyrolysis is not a satisfactory method of preparation especially for molecules carrying a variety of substituents.

Compounds of formula II may also be prepared by the Peterson reaction (J Organic Chem 1968,780; Carey and Toler ibid, 1976, 41, 1966, Hudrik & Peterson J Amer Chem Soc 1975,97, 1464) - see the scheme below.

An oxo compound of formula Vlil is treated with a silicon compound IX under the conditions of the Peterson reaction to give a silyl compound X which is treated under acidic or basic conditions to give compound II. If the conditions of work up are acidic (e.g. sulphuric acid or trifuloroacetic acid) then compound X will usually be converted first into a compound X where M is H, but basic conditions (e.g.

sodium or potassium hydride) and use of fluoride ions (e.g. KF or LiF) usually result in direct formation of compound II. In the silicon compound IX, Re and R7 are as previously defined in connection with formula I, M is an alkali metal especially lithium or MgHal where Mg denotes magnesium and Hal is chlorine, bromine or iodine, and the three R radicals may be the same or different and alkyl, cycloalkyl, aralkyl or aryl (which radicals may be as previously defined for R1, R2 etc.) or R is selected from electron donating substituents including alkoxy, cycloalkoxy, aralkoxy, aryloxy, alkylthio, cycloalkylthio, aralkylthio or arylthio, the group RbRCN- wherein Rb and RC are selected from alkyl, cycloalkyl, aryl and aralkyl (which radicals may be as previously defined for R1, R2 etc.) or Rb and RC may be joined to form a heterocyclic ring with the nitrogen atom (e.g. a piperidinyl or pyrrolidinyl ring, which may be substituted e.g. by alkyl). It is preferred that SiR3 is triloweralkylsilyl e.g. trimethylsilyl or triarylsilyl e.g. triphenylsilyl.

When the R radical is alkoxy or cycloalkoxy these radicals may be as defined above for R4 and R5. Aralkoxy and aryloxy radicals for R may be such radicals in which the aralkyl or aryl portions are as defined above for aralkyl or aryl radicals. Similarly when R radicals are alkylthio, cycloalkylthio, aralkylthio, or arylthio, the alkyl, cycloalkyl, aralkyl or aryl portions of these radicals may be as defined above for alkyl, cycloalkyl, aralkyl or aryl radicals.

The silicon compound IX starting materials may be prepared from corresponding compounds R3SiCHR3R7 by standard methods. The starting materials of formula VIII may be prepared as described in UK Patent Specification 1460457 or by analogous methods.

In a variation of the above reaction the compounds of formula II may be prepared by the following scheme:

A silicon compound of formula Xl, where R1, R2, R3, R4, R5, R and n are as previously defined and X is hydrogen, sodium, potassium or lithium is reacted with a carbonyl compound R6R7CO to obtain a silyl intermediate of formula XII which is converted to compound II by acid or base treatment as described for the previous reaction scheme. The starting compound Xl may be prepared as described in our UK Patent Application 8316273 (H-325 ) filed 15June 1983 or by analogous methods.Briefly a compound of formula

where M is sodium, potassium or lithium is treated with a silylating agent of formula R3SiHal where R is as defined above and Hal is chlorine, bromine or iodine, to obtain a compound of formula XI wherein X is hydrogen and if desired treating this with a metal compound R*M where M is sodium, potassium or lithium and R* is alkyl, cycloalkyl, aralkyl or aryl or an amine residue to obtain a compound of formula Xl where Xis sodium, potassium or lithium.

Alternatively compounds of formula II may be prepared by the Wittig reaction (see Peterson loc cit for references thereto).

The Wittig phosphorus reagent is prepared by reacting Ph3Pwith a compound R5R7CHBr.

Compounds of formula I may be used as intermediates for the preparation of the corresponding compounds of formula XIV

Compounds of formula XIV are intermediates for other compounds with anti-ulcer or anti-secretory activity eg. the compounds of UK Patent Specification No. 1432378.

The invention is illustrated by the following Examples.

EXAMPLE 1 3, 8-Dimethyl-5, 6, Z 8-tetrahydro quinoline A mixture of 3-methyl-5,6,7,8-tetrahydroquinoline (100 ml) paraformaldehyde (309) and acetic anhydride (100 ml) was heated at reflux for 30 hours. The residue was distilled to give a mixture of starting tetrahydroquinoline and 3,8-dimethyl-5,6-dihydroquinoline (40g) bp.126-180 /15mm. Chromatography on silica gel (500g,Woëlm active, 100-200) using di-isopropyl ether gave 3,8-dimethyl-5,6-dihydroquinoline (22g).

A solution of the dihydroquinoline (22g) in ethanol (200 ml.) was hydrogenated over 10% palladium on carbon (1 g) at 25 and 1 atmosphere. After the theoretical uptake had occurred (1.5 hours) the catalyst was removed by filtration, the filtrate evaporated and the residue distilled to give the title tetrahydroquinoline (22g) bp. 124'/15mm C11H15N requires: C,81.9; H,9.4; N,8.7%. Found: C,81.9, H,9.1, N,8.3% The catalyst in this example is a mixture of acetic anhydride and acetic acid, the acetic acid being produced in situ.

EXAMPLE 2 Compound present The reaction described in Example 1, st paragraph, was followed in a time course experiment, samples being taken at intervals and composition analysed by glc. (Pye 104 C20M T=200") Results were as follows:

Time 11/2 hours 20% 66% 7% 2 hours 21% 61% 11% 4 hours 22% 51% 20% 6 hours 23% 42% 26% 30 hours 22% 0 68% EXAMPLE 3 The reaction described in Example 1, 1st paragraph, was repeated employing various catalysts. The results are shown in the following table (for structures of compounds B and C - see Example 2).

Isomerisation of compound B to compound C using various catalysts.

Catalyst/Reaction Reaction time Percentage of Conditions (hours) Compound C CH3CO2H, reflux 30 100 NaOAc,5% Pd-C, EtOH, reflux 21.6 85.4 BF3-Et2O, dioxan, reflux 24 83 PPA, 100 1.5 76a H3PO4, H2O, reflux 21.6 25.1 ZnCl2, dioxan, reflux 30 22.5 (CH3CO)2O, reflux 30 5 KOH, EtOH, 22" 30 5 aSevere decomposition of compound C was observed after 2 hours.

PPA = Polyphosphoric acid EXAMPLE 4 [8R*]-5, 6, 8-tetrah ydro-8-([2S*]-2-(2-h ydroxy- l-phenyl)prop yl)-3-meth ylquinolin e

To a mixture of 5,6,7,8-tetrahydro-3-methylquinoline (209) and toluene (100 ml) was added 1.63 molar n-BuLi in hexane (93 ml) at 40at. The resulting anion solution was added to a mixture of phenylacetone (50 ml) and toluene (100 ml) at -40 C. The solution was allowed to warm to room temperature and the excess n-BuLi was quenched by adding 2N HC1 (90 ml). The excess solvent was removed by evaporation. The resultant aqueous mixture was basified with saturated aqueous NaHCO3 solution and extracted with EtOAc (3x 100 ml). The extracts were dried (MgSO4) and the solvent removed by evaporation.The mixture of products was separated by chromatography[SiO2; cyclohexane - CH3CO2CH3 (4:1)1. Upon removal of the solvent by evaporation the product crystallised to give the title compound (2.25 g), m.p. 99-101 0C. (Found: C,81.1; H,8.1; N,4.7. C19H23NO requires C,81.1; H,8.2; N,5.0%).

EXAMPLE 5 [8R*]-5,6, 7,8-tetrahydro-8-z[2R*]-2-62-hydroxy- 1-phen yl)prop yl(-3-m eth ylquin oline

To a mixture of 5,6,7,8-tetrahydro-3-methylquinoline (20 g) and toluene (100 ml) was added 1.63 molar n-BuLi in hexane (93 ml) at 40at. The resulting anion solution was added to a mixture of phenylacetone (50 ml) and toluene (100 ml) at 40"C. The resulting solution was allowed to warm to room temperature. The excess n-BuLi was quenched by adding 2N-HCI (90 ml). The aqueous layer was separated, basified with saturated aqueous NaHCO3 solution, and extracted with Et2O (3 x 100 ml). The ethereal extracts were dried (MgS04) and the solvent removed by evaporation. The mixture of products was separated by chromatogra phy [SiO2; cyclohexane - methyl acetate (80:20)]. The solvent was removed by evaporation and the residue dissolved in Et2O, to which an ethereal solution of HCI (50 ml) was added. The precipitate was collected by filtration, washed with Et2O, and dried in vacuo to give the title compound as a hydrochloride 11/2 hydrate (2.09 g) m.p. 98-100"C. (Found: C,66.2; H,7.5; N,3.9. C19H23NO.HCl. 3/2 H2O requires C,66.2; H,7.9; N,4.1%).

EXAMPLE 6 5, 6, 7,8-tetrahydro-8-{1-hydroxyethyl2-3-methylquinoline

To a mixture of 5,6,7,8-tetrahydro-3-methylquinoline (20 g) and dry THF (150 ml) was added 1.63 molar n-BuLi in hexane (108 ml) at -30 C. The resulting anion solution was added to a solution of acetaldehyde (50 ml) in anhydrous THF (50 ml) at -30 C. The solution was allowed to warm to room temperature. The excess n-BuLi was quenched with 2N-HCI (20 ml). The excess acetaldehyde and solvent were removed by evaporation. The resultant aqueous mixture was basified with saturated aqueous NaHCO3 solution and extracted with Et2O (3 x 100 ml). The ethereal extracts were dried (MgSO4) and the solvent removed by evaporation. The mixture of products was separated by chromatography (SiO2; EtOAc).The solvent was removed by evaporation and the residue dissolved in Et2O to which ethereal HCI (50 ml) was added. The product was removed by filtration, washed with Et2O and dried in vacuo to give the title compound as the hydrochloride 1/4 hydrate (1.13 g) m.p. 172-175 C. (Found: C,62.4; H,7.9; N,6.0 C12H17NO. HCi.1/4H2O requires C,62.1; N,8.0; N,6.0%).

EXAMPLE 7 5,6,7, 8-tetrahydro-8-(2 (2-hydroxy Ipropyl)-3-methylquinoline

To a mixture of 5,6,7,8-tetrahydro-3-methylquinoline (23.44 g, 159 mmol) and toluene (200 ml) was added 1.63 molar n-BuLi in hexane (108 ml) at -40 . After 15 mins. the resulting anion solution was added to a solution of acetone (100 ml) in toluene (200 ml). The solution was allowed to warm to room temperature and was treated with 2N-HCI (90 ml). The excess acetone was removed by evaporation in vacuo. The resultant aqueous mixture was basified with saturated aqueous NaHCO3 solution and extracted into Et2O (3 x 100 ml).

The ethereal extracts were dried (MgSO4) and the solvent removed by evaporation in vacuo. The mixture of products were separated by chromotography [SiO2; EtOAc-petrol (1 .4)j to give the free base (7.3039,22%) of the title compound as a red oil.

A small quantity of the free base (0.744 g) was dissolved in Et2O and treated with ethereal HCI. The product was removed by filtration, washed with Et2O, and dried in vacuo to give the title compound as the hydrochloride, m.p. 140-144". (Found: C,63.2; H,8.3; N,5.5 C13HlgNO.HCi.1/4H2O requires C,63.4; H,8.4; N,5.7%).

EXAMPLE 8 5,6,7,8-tetrahydro-3-methyl-8-(2-propylidene)quinoline

Experimental details A mixture of 5,6,7,8-tetrahydro-8-(2(2-hydroxy)propyl)-3-methylquinoline (3.044 g, 14.8 mmol) and polyphosphoric acid (20g) was vigorously stirred at 80-90 for 50 mins. and then poured into saturated aqueous Na2CO3 solution (200 ml). The aqueous solution was extracted with Et2O (2 x 100 ml) and the ethereal extracts dried (MgSO4) and evaporated in vacuo to give an oil. Purification by column chromatography [SiO2; hexane-propan-2-ol(1 :1)] and bulb-to-bulb distillation gave the title compound (1.855 9 67%) as a colourless oil, b.p. 150-50.1 mm Hg (Found: C,83.25; H,9.3; N,7.5C13H17N requires C,83.4; H,9.15; N,7.5%).

Claims

1. A process for preparing dihydro compounds of formula I

and acid addition salts thereof, wherein R1, R2, R3, R4, R5, Re and R7 are the same or different and represent hydrogen, or alkyl, cycloalkyl, aralkyl, or aryl radicals any of which radicals may be substituted, or R1 and R2 taken together or R2 and R3 taken together, form a 5, 6 or 7 membered ring which may be saturated or unsaturated and substituted or unsubstituted, R4 and R5 may also represent alkoxy, or cycloalkoxy, n is 1,2 or 3 and, if more than one R4 radical is present the R4 radicals may be the same or different and R6 and R7 represent hydrogen, alkyl, cycloalkyl, or aralkyl radicals, which process comprises re-arranging a compound of formula II

wherein R1, R2 R3, R4, R5, Re, R7 and n are as defined above.

2. A process as claimed in Claim 1, wherein the re-arrangement is carried out under acidic conditions.

3. A process as claimed in Claim 2, wherein the re-arrangement is carried out in the presence of a carboxylic acid, phosphoric acid, polyphosphoric acid, a Lewis acid or an acid anhydride.

4. A process as claimed in Claim 3, wherein the re-arrangement is carried out in the presence of acetic acid.

5. A process as claimed in Claim 1, wherein the re-arrangement is carried out in the presence of a noble metal catalyst.

6. A process as claimed in Claim 5, wherein the re-arrangement is carried out in the presence of a noble metal catalyst and a weak base.

7. A process as claimed in any one of Claims 1 to 6, wherein n is 2 and R', R2, R3, R4 and R5 are selected from hydrogen and alkyl of 1 to 6 carbon atoms.

8. A dihydro compound whenever prepared by a process as claimed in any one of Claims 1 to 7.

9. A dihydro compound of formula I

or an acid addition salt thereof, wherein R1, R2, R3, R4, Re, Re and R7 are the same or different and represent hydrogen, or alkyl, cycloalkyl, aralkyl, or aryl radicals any of which radicals may be substituted, or R1 and R2 taken together or R2 and R3 taken together, form a 5, 6 or 7 membered ring which may be saturated or unsaturated and substituted or unsubstituted, R4 and R5 may also represent alkoxy, or cycloalkoxy, n is 1,2 or 3 and, if more than one R4 radical is present the R4 radicals may be the same or different and Re and R7 represent alkyl, cycloalkyl, or aralkyl radicals with the proviso that Re and R7 are not both hydrogen when R', R2, R3, R4 and R5 are all hydrogen.

10. A compound of formula las claimed in Claim 9, wherein n is 2 and R1, R2, R3, R4 and R5 are selected from hydrogen and alkyl of 1 to 6 carbon atoms.

11. Acompound offormula

or an acid addition salt thereof, wherein R1 is alkyl of 1 to 6 carbon atoms and Re and R7 are selected from hydrogen and alkyl of 1 to 6 carbon atoms.

12. 3,8-Dimethyl-5,6-dihydroquinoline or an acid addition salt thereof.

13. A compound of formula II

or an acid addition salt thereof, wherein R1, R2, R3, R4 and R5, Re and R7 are the same or different and represent hydrogen, or alkyl, cycloalkyl, aralkyl, or aryl radicals any of which radicals may be substituted, or R1 and R2 taken together or R2 and R3 taken together, form a 5, 6 or 7 membered ring which may be saturated or unsaturated and substituted or unsubstituted, R4 and R5 may also represent alkoxy, or cycloalkoxy, n is 1, 2 or 3 and, if more than one R4 radical is present the R4 radicals may be the same or different and R5 and R7 represent alkyl, cycloalkyl, or aralkyl radicals with the provisos that (1) when R1, R2, R3, R4 and R5 are all hydrogen, Re and R7 are not both hydrogen, and (2) when R' and R3 are both phenyl and when R1 is methyl and R4 is methyl then R5 and R7 are not both methyl.

14. A compound of formula II, as claimed in Claim 13, wherein n is 2 and R1, R2, R3, R4 and R5 are selected from hydrogen and alkyl of 1 to 6 carbon atoms.

15. Acompound offormula

or an acid addition salt thereof wherein R1 is alkyl of 1 to 6 carbon atoms and Re and R7 are selected from hydrogen and alkyl of 1 to 6 carbon atoms.

16. 5,6,7,8-Tetrahydro-3-methyl-8-(2-propylidene) quinoline or an acid addition salt thereof.

17. 5,6,7,8-Tetrahydro-3-methyl-8(methyiene) quinoline or an acid addition salt thereof.

18. A compound of formula Ill

or an acid addition salt thereof, wherein R1, R2, R3, R4 and R5, Re and R7 are the same or different and represent hydrogen, or alkyl, cycloalkyl, aralkyl, or aryl radicals any of which radicals may be substituted, or R1 and R2 taken together or R2 and R3 taken together, form a 5,6 or 7 membered ring which may be saturated or unsaturated and substituted or unsubstituted, R4 and R5 may also represent alkoxy, or cycloalkoxy, n is 1, 2 or 3 and, if more than one R4 radical is present the R4 radicals may be the same or different and Re and R7 represent alkyl, cycloalkyl, or aralkyl radicals and esters of carboxylic acids wherein R1, R2, R3, R4, R5 and n are as defined above and Re and R7 are other than hydrogen when R1, R2, R3, R4 and R5 are all hydrogen and Re and R7 are not both methyl when R4 is methyl.

19. A compound of formula Ill as claimed in Claim 18, wherein n is 2 and R1, R2, R3, R4 and R5 selected from hydrogen and alkyl of 1 to 6 carbon atoms.

20. A compound of formula IIIA

or an acid addition salt thereof wherein R1 is alkyl of 1 to 6 carbon atoms and Re and R7 are selected from hydrogen, alkyl of 1 to 6 carbon atoms, cycloalkyl, or aralkyl of 1 to 12 carbon atoms.

21. [8R*]-5,6,7,8-([2S*]-2-(2-hydroxy-1 -phenyl)propyl)-3-methylquinoline, the 2R*isomer thereof, or an acid addition salt thereof.

22. 5,6,7,8-Tetrahydro-8-(2-hydroxy)propyl-3-methylquinoline or an acid addition salt thereof.

23. A process for preparing a compound of formula I as defined in Claim 1 wherein Re and R7 are hydrogen which process comprises treating a compound of formula IV

wherein R', R2, R3, R4 and R5 are as defined in Claim 1 and M is hydrogen, with formaldehyde (which may be in the form of paraformaldehyde) in the presence of an organic acid anhydride.

24. A process as claimed in Claim 23, wherein the organic acid anhydride is acetic an hydride.

25. A process as claimed in Claim 23 or 24 wherein a compound of formula IV is used in which n is 2 and R1, R2, R3, R4 and R5 are selected from hydrogen and alkyl of 1 to 6 carbon atoms.

26. A process as claimed in Claim 23, substantially as hereinbefore described in Example 1.

27. A compound of formula I, whenever prepared by a process as claimed in any one of Claims 23 to 26.

28. A process for preparing a compound of formula II as claimed in Claim 13, which process comprises dehydrating a compound of formula Ill as shown in Claim 18 wherein R1, R2, R3, R4, R5, Re, R7 and n are as defined in Claim 13.

29. A process as claimed in Claim 28 wherein the compound of formula il is as defined in any one of Claims 14to 17.

30. A process as claimed in Claim 28 or 29 wherein the dehydration is carried out using polyphosphoric acid or acetic an hydride.

31. A process as claimed in Claim 28 substantially as hereinbefore described in Example 8.

32. A compound of formula II whenever prepared by a process as claimed in any one of claims 28 to 31.

33. A process for preparing a compound of formula Ill as claimed in Claim 18, which process comprises treating a compound of formula IV as shown in Claim 23, wherein R1, R2, R3, R4, R5 and n are as defined in Claim 18 and M is hydrogen, an alkali metal, or MgHal where Hal is chlorine, bromine or iodine with a carbonyl compound of formula V

wherein Re and R7 are as defined in Claim 18, with the proviso that when Re and R7 are both hydrogen then M is hydrogen.

34. A process as claimed in Claim 33, substantially as hereinbefore described in any one of Examples 4, 5,6or7.

35. A compound of formula Ill, whenever prepared by a process as claimed in Claim 33 or Claim 34.

36. A process for preparing a compound of formula II, as claimed in Claim 13, which process comprises treating under acidic or basic conditions, a compound of formula X

wherein R1, R2, R3, R4, R5, Re, R7 and n are as defined in Claim 13, M is an alkali metal or MgHal where Hal is chlorine, bromine or iodine, and the three R radicals may be the same or different and alkyl, cycloalkyl, aralkyl or aryl (which radicals may be as previously defined for R', R2 etc.) or R is selected from electron donating substituents including alkoxy, cycloalkoxy, aralkoxy, aryloxy, alkylthio, cycloalkylthio, aralkylthio or arylthio, the group RbRCN- wherein Rb and RC are selected from alkyl, cycloalkyl, aryl and aralkyl (which radicals may be as previously defined for R1, R2 etc.) or Rb and RC may be joined to form a heterocyclic ring with the nitrogen atom (e.g. a piperidinyl or pyrrolidinyl ring, which may be substituted e.g. by alkyl).

37. A process for preparing a compound of formula II, as claimed in Claim 13, which process comprises treating under acidic or basic conditions, a compound of formula XII

wherein R1, R2, R3, R4, R5, Re, R7 and n are as defined in Claim 13, Xis hydrogen. sodium, potassium or lithium and R is as defined in Claim 36.

38. A process for preparing a compound of formula II, as claimed in Claim 13, which process comprises reacting a compound of formula VIII

wherein R1, R2, R3, R4, R5 and n are as defined in Claim 13, with a Wittig phosphorus reagent of formula Ph3P = CRIER7 wherein Re and R7 are as defined in Claim 13.

39. A compound of formula II whenever prepared by a process as claimed in any one of Claims 36 to 38.