Ruthenium-catalyzed formal [4 + 2] cycloaddition of alkynes with alkenes: formation of cyclohexenedicarboxylates via isomerization of alkynes and successive Diels–Alder reaction

Formal [4 + 2] cycloaddition of alkynes with electron-deficient alkenes, which affords 3,6-dialkyl-4-cyclohexene-1,2-dicarboxylates, was achieved using Ru(η6-1,3,5-cyclooctatriene)(η2-dimethyl fumarate)2 as a catalyst. The reaction mechanism consists of two steps, isomerization of an alkyne to conjugated dienes and successive Diels–Alder reaction of the generated dienes with an electron-deficient alkene.