Studies in decarboxylation. Part VIII. The gas-phase pyrolysis of βγ-acetylenic acids

Abstract

Some βγ-acetylenic acids are shown to undergo flash vacuum pyrolysis to give quantitative yields of an allene and carbon dioxide. At higher pressures the decarboxylation is obscured in some cases by competing reactions. Acetylenic acids decarboxylate faster than their olefinic counterparts, and the reaction is shown to involve a concerted 1,5-hydrogen shift. The participation of acetylenic bonds in electrocyclic reactions is discussed.