Regioselective synthesis of (E)-5-(tributylstannylmethylidene)-5H-furan-2-ones and (E)-3-(tributylstannylmethylidene)-3H-isobenzofuran-1-ones: Easy access to γ-alkylidenebutenolide and phthalide skeletons

Regio- and stereoselective synthesis of gamma-alkylidene-butenolides and gamma-alkylidenephthalides has been achieved through the palladium-catalysed tandem cross-coupling/cyclisation reactions of tributylstannyl-3-iodopropenoate or the 2-iodo benzoate derivatives with tributyltinacetylene. Iododestannylation occurred with inversion of the configuration of the exocyclic double bond in the case of butenolides, but with retention of configuration for the phthalide. The selectivity observed in the Stille reaction was found to be dependent on the nature of the vinyl or the aryl halide.