Enamines. Part II. The reaction of enamines with methyl vinyl ketone

Abstract

The reaction of NN-dimethylisobutenylamine with methyl vinyl ketone gives 2-dimethylamino-3,3,6-trimethyl-3,4-dihydro-2H-pyran as the first formed product. The structure was deduced from extensive spectroscopic examination of the adduct. The chemical reactions of the adduct, however, indicated a ready equilibration of the dihydropyran with methyl 2-dimethylamino-3,3-dimethylcyclobutyl ketone through the immonium enolate intermediate. Other enamines and vinyl ketones appear to behave similarly.