Enamine chemistry. Part IV. Reaction of αβ-unsaturated acid chlorides with enamines of aldehydes

Abstract

The reaction of acryloyl chloride with 2-methyl-1-piperidinopropene in boiling benzene gives 2,2,6,6-tetramethyl-3-oxoheptane-1,7-dial, whereas crotonoyl and cinnamoyl chlorides give mixtures of the corresponding unsaturated 2-acyl-2-methylpropanal and unsaturated carboxamide. 2-Methyl-1-(pyrrolidin-1-yl)propene and crotonoyl chloride react at room temperature to give an iminium salt which may be hydrolysed to a 2-dihydropyranyl-2-methylpropanal or be converted by heat into a second iminium salt which on hydrolysis gives 2,2,5,6,6-pentamethyl-3-oxoheptane-1,7-dial. The reaction mechanism is discussed.