Process for the preparation of 2-substituted-5-(1-alkylthio)alkylpyridines

1. A process for the preparation of a 2-substituted-5-(1-alkylthio)alkylpyridine (I),

wherein either

R 1 or R 2 taken together with R 3 represent a 4- to 6-membered saturated ring and the non-selected R 1 or R 2 is a H, C 1 -C 4 alkyl, or

R 1 taken together with R 2 represents a 3- to 6-membered saturated ring optionally substituted with an O or a N atom; and

R 3 represents C 1 -C 4 alkyl or R 3 taken together with either of R 1 or R 2 represent a 4- to 6-membered saturated ring; and

R 4 represents C 1 -C 4 alkyl or C 1 -C 4 haloalkyl;

which comprises cyclizing an α,β-unsaturated ketone II

wherein

X represents halogen, OR 5 OSO 2 R 5 , SR 5 , SOR 5 , SO 2 R 5 or NR 6 R 7 ;

R 5 represent hydrogen, C 1 -C 8 alkyl, C 2 -C 8 alkenyl, C 1 -C 8 arylalkyl, C 1 -C 8 haloalkyl, C 1 -C 8 alkoxyalkyl, C 1 -C 8 alkylaminoalkyl, aryl or heteroaryl; and

R 6 and R 7 independently represent hydrogen, C 1 -C 8 alkyl, C 2 -C 8 alkenyl, C 1 -C 8 arylalkyl, C 1 -C 8 haloalkyl, C 1 -C 8 alkoxyalkyl, C 1 -C 8 alkylaminoalkyl, aryl or heteroaryl or R 6 and R 7 taken together with N represent a 5- or 6-membered saturated or unsaturated ring; and

R 4 is as previously defined;

with an enamine III

wherein

R 1 , R 2 , R 3 , R 6 , R 7 are as previously defined;

in the presence of ammonia or a reagent capable of generating ammonia.

2. The process of claim 1 in which the reagent capable of generating ammonia is an ammonium salt of an organic acid.