Novel Synthesis of Five- and Six-Membered Spiro γ-Lactones in Rigid Bicyclic Systems

Article abstract of DOI:10.1021/jo00141a028

The reaction of bis(bromomagnesio)alkanes with bridged tricyclic endo- and exo-dicarboxylic anhydrides and their dihydro derivatives provides a general and versatile route to corresponding tricyclic spiro γ-butanolides.Futher extension of this methodology to the dianhydride of bicyclo<2.2.2>octene showed appreciable regioselectivity.The subsequent transformation of spiro γ-lactones into 4-spiro-2-butenolides by retro-Diels-Alder reaction has provided a simple and convenient synthesis of these molecules.Proton and 13C NMR spectra are reported for most of the compounds.