Addition reactions of heterocyclic compounds. Part LVIII. Reactions of nitrogenous heterocycles with acetylacetylene

Abstract

Simple pyridines react with acetylacetylene and proton donors at –20° to give high yields of (E)-1-(3-oxobut-1-enyl)-1,4-dihydropyridines, while in the absence of such donors low yields of other compounds are isolated. Acetylacetylene reacts with 4-aminopyridine to give 4-[(E)-3-oxobut-1-enylimino]-1,4-dihydropyridine, imidazoles give the 1-[(E)-3-oxobut-1-enyl] derivatives, methyl 2-pyridylacetate yields quinolizines, and pyrrole the 2-[(E)-3-oxobut-1-enyl] derivative and 4,6-diacetylindole. The structures of these products and of minor components, are deduced mainly from their n.m.r. spectra.