Methyl Cyclopentadienecarboxylate Formation in the Methanol Quenched Vapor Phase Thermolysis of Methyl Salicylate

Abstract

Cyclopentadienylidenecarbonyl, the principle thermolytic fragment of methyl salicylate in the vapor phase, undergoes a rapid recombination with the methanol liberated in the initial fragmentation to yield monomeric methyl cyclopentadienecarboxylate. Reaction of this last ester with some dienophiles is reported, and, in the case of dimethyl acetylenedicarboxylate, adducts are obtained that suggest that the ester exists as a mixture of 1- and 2-substituted cyclopentadienes. No trace is found of a neutral fragment of mass 120 corresponding to the base peak in the 70 eV spectrum of methyl salicylate.