Method for producing substituted thiopyridines

A process for preparing sulfoxides of the formula Ib or sulfones of the formula Ic

• where
• R1,R2,R3 and R4 are identical or different and each is hydrogen, halogen, nitro, cyano, C1-C6-alkyl, C2-C6-alkenyl, C2-C6-alkynyl, C1-C6-alkoxy, C2-C6-alkenyloxy, C3-C6-alkynyloxy, C1-C6-alkylthio, C2-C6-alkenylthio, C3-C6-alkynylthio, C1-C6-alkylsulfinyl, C2-C6-alkenylsulfinyl, C3-C6-alkynylsulfinyl, C1-C6-alkylsulfonyl, C2-C6-alkenylsulfonyl, C3-C6-alkynylsulfonyl, the alkyl, alkenyl and alkynyl moieties of these groups optionally substituted with up to 6 halogen atoms;
• a C1-C4-alkylenephenyl, phenyl, phenoxy or naphthyl radical wherein the phenyl and naphthyl moieties are unsubstituted or substituted with halogen, C1-C3-alkyl, C1-C3-alkoxy, trifluoromethyl, cyano or nitro;
• COOR6, CONR7R8, SO2NR7R8 or COR6;
• the pyridine
• R5 is an unsubstituted or substituted C1-C10-alkyl, C2-C10-alkenyl or C2-C10-alkynyl radical said substituents being halogen, C1-C4-alkoxy, C1-C4-alkoxycarbonyl, di-(C1-C4-alkyl)aminocarbonyl, cyano or nitro, a C3-C8-cycloalkyl radical, a C1-C4-alkylenephenyl, phenyl or naphthyl radical wherein the phenyl and naphthyl moieties are unsubstituted or substituted with halogen, C1-C3-alkyl, C1-C3-alkoxy, trifluoromethyl, cyano or nitro,
• R6, R7 and R8 are identical or different and each is hydrogen, C1-C6-alkyl, C3-C6-cycloalkyl, C2-C6-alkenyl, C3-C6-alkynyl, optionally these groups are substituted with up to 6 halogen atoms;
• a phenyl or C1-C4-alkylenephenyl radical wherein the phenyl moiety is unsubstituted or substituted by halogen, C1-C3-alkyl, C1-C3-alkoxy, trifluoromethyl, cyano or nitro,
• which comprising reacting substituted 2-halopyridines of the formula II
• in which R1, R2, R3 and R4 are each as defined above and Hal is fluorine, chlorine or bromine, in a first step with a thio compound of the formula III
• HS—R5 III
• in which R5 is as defined above, in the presence of a copper catalyst to give initially a pyridine thioether of the formula Ia
• and then oxidizing this stepwise to give the sulfoxide Ib or sulfone Ic.