Patent ID: 8785480

Claim:
A process for the preparation of a 2-substituted-5-(1-alkylthio)alkyl-pyridine N-oxide according to formula (I), wherein L represents a single bond or R 1 , S and L taken together represent a 4-, 5- or 6-membered ring; R 1 represents (C 1 -C 4 ) alkyl; R 2 and R 3 individually represent hydrogen, methyl, ethyl, fluoro, chloro or bromo; n is an integer from 0-3; and Y represents (C 1 -C 4 ) haloalkyl; in which: i) an enamine according to formula (II) wherein R 1 , R 2 , R 3 , L, and n are as previously defined, and R 4 and R 5 independently represent 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 4 and R 5 taken together with N represent a 5- or 6-membered saturated or unsaturated ring is condensed with an α,β-unsaturated ketone according to formula (III) wherein Y is as previously defined; and X 1 represents halogen, OR 6 , OSO 2 R 6 , SR 6 , SOR 6 , SO 2 R 6 or NR 7 R 8 , where R 6 represents 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 7 and R 8 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 7 and R 8 taken together with N represent a 5- or 6-membered saturated or unsaturated ring; to provide an intermediate compound according to formula (IV) wherein R 1 , R 2 , R 3 , R 4 , R 5 , L and n are as previously defined; and ii) the intermediate compound according to formula (IV) is cyclized using an amine nucleophile according to formula (V) H 2 N—X 2 (V) wherein X 2 represents hydroxyl.