Addition reactions of heterocyclic compounds. Part XLVI. Reactions of acetylenic esters with pyridines in the presence of proton donors, and with alkyl 3-(2-pyridyl)-trans-acrylates

3,5-Dimethylpyridine and methyl propiolate gave methyl [1,2-dihydro-1-(trans-2-methoxycarbonylvinyl)-3,5-dimethyl-2-pyridyl]propiolate. Addition of methanol to the reaction media, as with other pyridines, gave the corresponding 1,2-dihydro-2-methoxy-1-(methoxycarbonylvinyl)pyridines, whereas addition of water yielded dihydropyridines with a divinyl ether side-chain. Addition of phenol gave only phenoxyacrylates. Ethyl 3-(2-pyridyl)-trans-acrylate with acetylenic mono- and di-esters gave 4H-quinolizines via a spiro-intermediate, with the apparent migration of an ester group.