Selective Catalytic Methoxycarbonylmethylenation of the Triple Bond of Vinylacetylene with Methyl Diazoacetate

Selective RH₂(OAc)₄-promoted methoxycarbonylmethylenation of the triple bond of vinylacetylene with methyl diazoacetate results in methyl 1-vinylcyclopropene-3-carboxylate 1, which [2 + 2]cyclodimerizes in situ to give dimethyl trans-1, 2-divinyltricyclo[3.1.0.0^2,4]hexane-3,6-dicarboxylate 2.