Formation of ω-(4-oxo-1,4-dihydropyridin-2-yl)alkanamides in the Beckmann rearrangement of spiro-fused cycloalkanone oximes

TLDR: In this paper, cycloalkanone oximes were spirofused to 4-oxo-6-methyl-1,2,3,4-tetrahydropyridine fragment through the α-carbon atom and C2, respectively, on heating in polyphosphoric acid.

Abstract: ω-(4-Oxo-1,4-dihydropyridin-2-yl)alkanamides were obtained from cycloalkanone oximes spirofused to 4-oxo-6-methyl-1,2,3,4-tetrahydropyridine fragment through the α-carbon atom and C2, respectively, on heating in polyphosphoric acid. The resulting amides were converted to the corresponding acids and methyl esters. Methylation of 5-(6-methyl-4-oxo-1,4-dihydropyridin-2-yl)pentanamide with diazomethane gave 4-methoxypyridine derivative as the major product and a small amount of N-methyl derivative, 5-(1,6-di-methyl- 4-oxo-1,4-dihydropyridin-2-yl)pentanamide.