Thermal Rearrangements of Cyclic Amine Ylides. IV. Rearrangement of β,ϒ-Unsaturated 1-Alkylpiperidine N-Oxides: Formation of 1,2-Oxazepine Derivatives

Abstract

The thermolysis of 1-methyl-2-vinylpiperidine N-oxide (13) resulted in Meisenheimer [1,2] rearrangement to give the hexahydro-1,2-oxazepine (23) and no [2,3]-sigmatropic rearrangement product (24). Similarly, the 1 -methyl-1,2,5,6-tetrahydropyridine N-oxides (15), on heating, gave only the tetrahydro-1,2-oxazepines (26, 27), together with the Hofmann-type elimination products (28). The thermolysis of 1-benzyl-2-phenyl-(20a) and 1-benzyl-2-vinyl-piperidine N-oxide (20b) afforded the corresponding 1-benzyloxypiperidines (32) as well as the 1,2-oxazepines (31). These results are different from those observed for open-chain allylamine N-oxides and 1-alkyl-2-vinylpiperidine N-imides and N-ylides, which are known to undergo only [2,3]-sigmatropic rearran gement. © 1984, The Pharmaceutical Society of Japan. All rights reserved.