A reinvestigation of the stevens rearrangement of 1,3,4‐trimethyl‐1‐(3,4,5‐trimethoxybenzyl)‐1,2,5,6‐tetrahydropyridinium chloride

1,3,3‐Trimethyl‐2‐(3,4,5‐trimethoxyphenyl)‐4‐methylenepiperidine (XI) is prepared in an unambiguous way which involves the Refortmatsky reaction followed by ethanolysis on the N ‐(3,4,5‐trimethoxybenzylidene)methylamine, later treatment of the resulting aminoester with ethyl acrylate, ring closure by Dieckmann reaction with decarbalkoxylation and, finally, a Wittig reaction on the piperidone obtained. The resulting methylenepiperidine XI differs in its physical and spectroscopic data from the methylene derivative IIIa obtained by the Stevens rearrangement of the 1,3,4‐trimethyl‐1‐(3,4,5‐trimethoxybenzyl)‐1,2,5,6‐tetrahydropyridinium chloride, whose structure must be reviewed.