GB2250286A

GB2250286A - Aromatic zinc compound and their use in the preparation of phenylpyridylpyrimidines

Info

Publication number: GB2250286A
Application number: GB9111896A
Authority: GB
Inventors: Brian Leslie Pilkington
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1990-06-11
Filing date: 1991-06-03
Publication date: 1992-06-03
Also published as: KR920000767A; DE4118430A1; FR2663032A1; GB9111896D0; JPH04243875A; GB9012974D0

Description

2250236 CHEMICAL PROCESS This invention relates to a process for the

preparation of 2-phenyl-6- (pyrimidin-2-yl)pyridine derivatives, to intermediate compounds used therein and to processes for preparing the intermediate compounds.

According to the present invention there is provided a process for the preparation of a compound of formula (V), wherein V, Y and Z are independently hydrogen, chlorine, fluorine, alkyl or alkoxy, the process comprising treating a compound of formula (IV), wherein Wt Y and Z are as defined above, with zinc (II) chloride.

In one aspect the present invention provides a process for the preparation of a compound of formula (V), wherein V, Y and Z are as defined above, the process comprising the steps of: a) lithiating a compound of formula (VIII), where W, Y and Z are as defined above and X is bromine or iodine; and, b) treating the product formed in (a) with zinc (II) chloride.

In another aspect the present invention provides a process for the preparation of a compound having the general formula (1), wherein W; Y and Z are as defined above, R 1, R 2 and R 3 are independently hydrogen, alkyl, haloalkyl or alkoxy and R 4, R 5 and R6 are independently hydrogen, chlorine, fluorine, alkyl, haloalkyl or alkoxy, or R 4 and R 5 together form a polymethylene group of the formula -(CH 2)m- in which m is 3 or 4; the process comprising the steps of: a) lithiating a compound of formula (VIII), wherein X, V, Y and Z are as defined above; b) treating the product so formed in (a) with zinc (II) chloride; and c) reacting the product so formed in (b) with a compound of formula (III), in the presence of a suitable catalyst.

The invention includes the steps (b) and (c) individually or in combination.

The process is particularly useful for the preparation of compounds having the general formula (I) wherein W, Y, Z, R 1, R 2, R 3, R 5 and R 6 are all hydrogen and R 4 is methyl.

A suitable compound of formula (VIII) is 2-chlorobromobenzene.

Alkyl and the alkyl moieties of alkoxy and haloalkyl groups contain from 1 to 6, preferably 1 to 4, carbon atoms and are either straight or branched chain groups, for example, methyl, ethyl, n-propyl, iso-propyl, nbutyl, iso-butyl, sec-butyl or tert-butyl- Compounds having the general formula (I) are disclosed in (EP-A-259139) and are useful as fungicides.

The process of the invention is shown in Scheme A. Throughout Scheme A the variables W, Y, Z, X, R I, R 2, R 3, R 4, R 5 and R6 are as defined above.

In step (a) a compound of formula (VIII) is lithiated preferably with an alkyl lithium (for example n-butyl lithium) in a suitable solvent (such as tetrahydrofuran) at a suitable temperature (such as -70 to -1000C, preferably -70 to -78C) to give a product (IV). It is believed that product (IV) has the general formula (IV).

In step (b) the product formed in step (a) (product (IV)) is reacted with zinc (II) chloride in a suitable solvent (for example diethylether) at a suitable temperature (such as in the range -60 to -80C, preferably in the range -70 to -78C) to give a product (V). It is believed that product (V) has the general formula (V).

In step (c) product (V) is reacted with a compound of general formula (III) in the presence of a suitable catalyst (for example tetrakis(triphenylphosphine) palladium.0) in a suitable solvent (for example tetrahydrofuran) and at a suitable temperature.

Compounds of general formula (III), in which R 1, R 2, R 3, R 4, R 5 and R 6 are as defined above, can be prepared by coupling together a dibromopyridine of general formula (VI), wherein R I, R 2 and R 3 are as defined above, with a bromopyrimidine of general formula (VII), wherein R 4 R 5 and R 6 are as defined above. The coupling reaction can be carried out by treating the dibromopyridine (VI) with normal butyl lithium in tetrahydrofuran followed by zinc (II) chloride in diethylether, and then adding tetrakis(triphenylphosphine)palladium with the bromopyrimidine (VII). The reaction is carried out at temperatures of between -70 and 20C.

In a further aspect the present invention comprises the product of the process comprising the steps of: a) lithiating a compound of formula (VIII), wherein X, V, Y and Z are as defined above; and, b) taking the product so formed and reacting it with zinc (II) chloride.

In another aspect the present invention comprises the product of the process of treating a compound of formula (IV), wherein W, Y and Z are as defined above, with zinc (II) chloride.

In a still further aspect the present invention comprises a compound having the general formula (V).

j The following Example illustrates the present invention. Where shown, NMR data are selective; no attempt is made to list every absorption. The following abbreviations are used throughout:

THF = tetrahydrofuran dd = doublet of doublets d = doublet t = triplet S = singlet EXAMPLE 1 This Example illustrates the preparation of 4-methyl-2-(6-(2- chlorophenyl)pyrid-2-yl)pyrimidine, as shown in Scheme B. Reactants 2- chlorobromobenzene (Aldrich) 0.57g (2.98mM) n-butyl lithium 2.5M in hexanes (Aldrich) 1.7ml (4.27mM) zinc (II) chloride LOM in ether (Aldrich) 10ml (lOmM) 4-methyl-2-(6-bromopyrid-2-yl)pyrimidine 0.5g (2mM) tetrakis(triphenylphosphine)palladium 0.05g (catalyst). Method 2-Chlorobromobenzene (dried over molecular sieve 4A) was dissolved in tetrahydrofuran (10ml - freshly distilled from sodium and benzophenone) in dry apparatus under an atmosphere of nitrogen. The resulting solution was then cooled, with stirring, (using a solid CO 2 /acetone bath) to - 78C and a solution of n-butyl lithium was added over 15 minutes at a temperature below 70'C. The colourless solution was then stirred at -78C for 15 minutes before adding the anhydrous zinc (II) chloride solution at below -70C over a period of 20 minutes. The resultant white suspension was stirred at -780C for 30 minutes before adding a solution of 4-methyl2-(6bromopyrid-2-yl) pyrimidine and tetrakis(triphenylphosphine)palladiumO in THF (10ml freshly distilled from sodium/benzophenone). The reaction mixture was then allowed to warm up to room temperature to give a pale yellow solution, from which a white solid began to precipitate. The mixture was then heated to reflux for 30 minutes before cooling and quenching by the addition of a 10% aqueous solution of ethylene diamine tetra acetic acid sodium salt (150ml at pH8). The two layers were seperated and the aqueous solution was extracted with ethyl acetate (2x5Oml). The organic solutions were combined, dried over magnesium sulphate (anhydrous) and evaporated to give a bright yellow gum - yield 0.9g. The gum was purified by flash vacuum chromatography through a 40mmx4Omm diameter plug of silica gel (Merck 7729) eluting with 1x50C dichloromethane then 4x50m1 portions of methyl-t-butyl ether. Fractions 3 to 5 were combined to give a pale yellow gum. Yield 0.397g (70.5%), which solidified on standing. The solid was recrystallised from 10% ethyl acetate in hexane to give lustrous white plates. Mpt. 123.8 - 124.PC. Proton NMR in CDC1 3 at 270 MHz: 7.47(dd); 7.36(m); 7.77(d); 7.92(t); 8. 48(d); 8.79(d); 7.28(d); 2.66(s) ppm. Synthesis of 4-methyl-2-(6bromapyrid-2-yl)pyrimidine 2,6-Dibromopyridine (9.48g, 40mM) was dissolved in tetrahydrofuran (100m1 freshly distilled from sodium/benzophenone) under nitrogen. The solution was then cooled in a solid CO 2 /acetone bath and n-butyl lithium (2.5 molar solution in hexane - 24m1 60mM) was added with stirring over 30 minutes at below -700C. The dark green solution was then stirred at -780C for 1 hour after which time a small sample was removed, quenched by addition of water and extracted with ethyl acetate. Gas chromatography analysis showed only 2-bromopyridine to be present. At this point an anhydrous solution of zinc (II) chloride (1.0 molar in diethylether 120m1 120mM) was added over 30 minutes with the reaction temperature below - 701C. During the addition the colour became a paler green and a green gum precipitated. A solution of tetrakis(triphenylphpsphine)palladium (1.Og catalyst) and 2-bromo-4-methylpyrimidine (9.6g, 39.9mM) in tetrahydrofuran (100C freshly distilled from sodium/benzophenone) was then added over 30 minutes at below -701C. The reaction mixture was allowed to warm up to room temperature before refluxing for 1 hour. After cooling to room temperature the reaction was quenched by pouring into a 10% solution of sodium ethylene diaminetetraacetate in water at pH8 (500m1) and extracting with ethyl acetate (3x500m1). The combined ethyl acetate extracts were washed once with water (100m1), dried over magnesium sulphate and evaporated to give a brown gum (12.1g).

The gum was purified by medium pressure preparative liquid chromatography using silica gel 60 (40-60 micron) and eluting with ethyl acetate to give the product as a pale brown solid. Yield 3.15g (31.5%) The solid was recrystallised from ethyl acetate m.pt 134.5 to 135.10C N.M. R. proton shifts in CDC1 3 at 270 MHz: 7.60(dd); 7.71(t); 8.46(dd); 8. 78(d); 7.19(d); 2.76(s) ppm.

CHEMICAL FORMULAE (in description) cl v 1 -:,, y z R 1 R 2 R 3 4 N NN R R (I) R 6 X cl Z', 1 ";;- W y R R 3 N N Br N R 4 R 5 R 6 (VIII) (III) - 6 CHEMICAL FORMULAE (in description)

Li cl 1 ZJO v ZnCl cl 1 z 'i y R2 R 1 1 N Br B 6 R -/ - N \, N - R1 5 Br (IV) (VI) (Vii) Scheme A X 1 cl ---- li::

y V U, Product (IV) W Product (V) y (Viii) step (a) step (b) R 21 step (c) 1 ', R 3 cl ";" 1 W N N (I) 1 1-t.1 1 1 11 N, - R 5 R 6 z (I) R 4 Scheme B Br 6"Z -- 1 cl n-BuMITHF 1 1011 4 cl1. "- N "-' -- 17-N :' 1 N - Z:-1 1 (1 1.5 Li cl zncl 2 /diethylether -700c CH 3 ZnCl cl 5::P, 1/ :-11 t,'

Claims

1. A process for the preparation of a compound of formula (V):

ZnCl %0 1 cl 1 Z / V Y (V) wherein W, Y and Z are independently hydrogen, chlorine, fluorine, alkyl or alkoxy, the process comprising treating a compound of formula (IV):

Li 0111, 1 Cl Z Z I W j I Y (IV) wherein W, Y and Z are as defined above, with zinc (II) chloride.

2. A process as claimed in claim 1 for the preparation of a compound of formula (V):

ZnCl ---- 1 cl Z W Y (V) wherein W, Y and Z are as defined in claim 1, the process comprising the steps of:

a) lithiating a compound of formula (VIII):

X 1 "R cl 1 li:

Z j v Y (VIII) wherein W, Y and Z are as defined in claim 1 and X is bromine or iodine; and b) treating the product formed in (a) with zinc (II) chloride.

A process for the preparation of a compound having the general formula (I):

cl v 1 Y R 1 R 2 R

3 N N R

4 N R (I) R 6 wherein W, Y and Z are independently hydrogen, chlorine, fluorine, alkyl or alkoxy, R', R 2 and R3 are independently hydrogen, alkyl, haloalkyl or alkoxy and R 4, R 5 and R 6 are independently hydrogen, chlorine, fluorine, alkyl, haloalkyl or alkoxy, or R 4 and R5 together form a polymethylene group of the formula -(CH2)m- in which m is 3 or 4; the process comprising the steps of: a) lithiating a compound of formula (VIII):

X cl Z', 1 'I 11 Y (VIII) Z 11 - wherein W, Y and Z are as defined above and X is bromine or iodine; b) treating the product so formed in (a) with zinc (II) chloride; and c) reacting the product so formed in (b) with a compound of formula (III):

R 2 R 1 R 3 1 Br N N R 4 Q;Z 1 N - R 5 R 6 in the presence of a suitable catalyst.

(III) A process as claimed in claim 1, 2 or 3 wherein W, Y and Z are all hydrogen.

5. The product of the process comprising the steps of: a) lithiating a compound of formula (VIII):

X cl Z "" 11 1 V Y (VIII) wherein W, Y and Z are independently hydrogen, chlorine, fluorine, alkyl or alkoxy; and X is chlorine or bromine; and, b) taking the product so formed and reacting it with zinc (II) chloride.

6. A compound having the general formula (V):

ZnCl cl 1 Z 11 Y (V) wherein V, Y and Z are independently hydrogen, fluorine, chlorine, alkyl or alkoxy.

The product of the process comprising treating a compound of formula (IV):

1 1 cl Z W Li (IV) Y wherein W, Y and Z are as defined in claim 1, with zinc (II) chloride.

8. A proress as claimed in claim 3 substantially as hereinbefore described with reference to Example 1.