Orthoamides and iminium salts, XCVIa. Push-pull-substituted 1,3,5-hexatrienes from orthoamides of alkyne carboxylic acids and Birckenbach-analogous acetophenones

摘要

From acetone and the orthoamide of phenylpropiolic acid (21b) N,N-dimethyl-phenylpropiolic acid amide (24) is formed. In contrast, the reaction of chloroacetone (28) with 21b results in the vinylogous guanidinium chloride 29. Unexpectedly, the Birckenbach-analogoue ethyl methyl ketone (34) reacts with the orthoamide 21b to give the push-pull-substituted butadiene 36. In contrast to this observation, the reaction of the Birckenbach-analogous acetophenones 30 with the orthoamides 21a-c delivers the push-pull-substituted 1,3,5-hexatrienes 31a-j.