PYRIDINE-N-OXIDES AND PROCESSES FOR THEIR PREPARATION Russian patent published in 2017 - IPC A01N43/40 

FIELD: chemistry.

SUBSTANCE: for the preparation of the 2-substituted-5-(1-alkylthio)-alkyl-pyridine-N-oxide corresponding to formula (I):

where L is a single bond or R1, S and L taken together are 4-, 5- or 6-membered ring; R¹ is (C₁-C₄) -alkyl; R² and R³ are individually hydrogen, methyl, ethyl, fluoro, chloro or bromo; N is an integer from 0 to 3; And Y is (C₁-C₄)-haloalkyl; In which: (i) the enamine corresponding to formula (II):

,

where R¹, R², R³, L and n are as defined above; And R⁴ and R⁵ are independently 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, α-unsaturated ketone corresponding to formula (III):

,

where Y is as defined above; and X¹ is halogen, OR⁶, OSO₂R⁶, SR⁶, SOR⁶, SO₂R⁶ or NR⁷R⁸, where R⁶ is 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 are independently hydrogen, C₁-C₈-alkyl, C_2-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 are a 5- or 6-membered saturated or unsaturated ring; to obtain an intermediate corresponding to formula (IV):

,

where R¹, R², R³, R⁴, R⁵, L and n are as defined above; and (ii) the intermediate corresponding to formula (IV) is cyclized using an amine nucleophile corresponding to formula (V): H₂N-X², wherein X² is hydroxyl, alkoxy, cyano, amino or mercaptan.

EFFECT: invention enables realisation of the mentioned purpose.

21 cl, 2 tbl, 7 ex