α-Methylene-β-lactones as novel allene equivalents: Regioselective [4 +2] cycloaddition and stereoselective decarboxylation for the introduction of exo-alkylidene functionalities

Article abstract of DOI:10.1016/0040-4039(91)85032-Z

β-Lactone-capped allene dienophiles afforded with cyclopentadiene spiro-β-lactone as [4+2] cycloadducts, which on thermal decarboxylation gave regio- and stereoselectively E-5-alkylidene 2-norbornenes.