Functionalized pyridine n-oxides and processes for the preparation of the same

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 R1, S and L taken together represent a 4-, 5- or 6-membered ring;
• R1 represents (C1-C4) alkyl;
• R2 and R3 individually represent hydrogen, methyl, ethyl, flouro, chloro or bromo;
• n is an integer from 0-3;
• and
• Y represents (C1-C4) haloalkyl;
• in which:
• i) an enamine according to formula (II)
• wherein
• R1, R2, R3, L, and n are as previously defined, and
• R4 and R5 independently represent C1-C8 alkyl, C2-C8 alkenyl, C1-C8 arylalkyl, C1-C8 haloalkyl, C1-C8 alkoxyalkyl, C1-C8 alkylaminoalkyl, aryl or heteroaryl or R4 and R5 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
• X1 represents halogen, OR6, OSO2R6, SR6, SOR6, SO2R6 or NR7R8, where R6 represents hydrogen, C1-C8 alkyl, C2-C8 alkenyl, C1-C8 arylalkyl, C1-C8 haloalkyl, C1-C8 alkoxyalkyl, C1-C8 alkylaminoalkyl, aryl or heteroaryl, and R7 and R8 independently represent hydrogen, C1-C8 alkyl, C2-C8 alkenyl, C1-C8 arylalkyl, C1-C8 haloalkyl, C1-C8 alkoxyalkyl, C1-C8 alkylaminoalkyl, aryl or heteroaryl or R7 and R8 taken together with N represent a 5-or 6-membered saturated or unsaturated ring;
• to provide an intermediate compound according to formula (IV)
• wherein
• R1, R2, R3, R4, R5, 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)
• H2N—X2 (V),
• wherein X2 represents hydroxyl, alkoxy, cyano, amino or mercaptan.