Addition reactions of heterocyclic compounds. Part LXI. Reactions of electrophilic acetylenes with conjugated cyclic enamines
[1-Alkylpyridin-4(1H)-ylidene] acetates and related compounds react at the exocyclic double bond with electrophilic acetylenes to give 1 : 1 and 1 : 2 adducts by simple Michael addition followed by proton shift. With tetracyanoethylene a related product was isolated and also a compound in which the ester group had been lost. Methyl [1-alkylpyridin-2(1H)-ylidene] acetates give analogous products with methyl propiolate, but-3-yn-2-one, and 4-phenylbut-3-yn-2-one.