Regio- and stereoselective synthesis of γ-alkylidenebutenolides and γ-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.
cross-coupling - cyclisation - alkylidenebutenolides - phthalides - retinoids