Reactions of Allenes. I. The Synthesis of Unsaturated Monocarboxylic Esters by the Carboxylation Reaction of Allenes; Reaction Conditions and Products

Abstract

Abstract The carboxylation reaction of propadiene and 1,2-hexadiene with carbon monoxide and methanol in the presence of a catalyst was studied. Propadiene was carboxylated to give methyl methacrylate in a fairly good yield (62% based on the propadiene consumed) by the use of a catalyst composed of nickel carbonyl and methacrylic acid or water under a relatively low pressure. A small amount of methyl vinylacetate was also present. The predominant side reaction was a polymer formation reaction. The carboxylation of 1,2-hexadiene, however, did not proceed smoothly, and a great amount of tarry materials was obtained. The carboxylation products obtained in low yields (max. 15%) were exclusively the materials formed by a carbonyl attack on the central carbon of the allenic structure, that is, methyl trans-2-methyl-2-hexenoate and methyl 2-butyl-2-propenoate.