LiBF4: A mild lewis acid for intramolecular diels-alder reactions

Article abstract of DOI:10.1016/S0040-4039(00)74269-9

The lithium salts, LiClO₄ and LiBF₄, have been investigated for their potential use as Lewis acid catalysts in the intramolecular Diels-Alder reaction. No cycloaddition of the trienone, 1, is observed when LiClO₄ is used. LiBF₄ provides quantitative yield of the cis-fused cycloadduct in 72 hours at room temperature. The catalysis is ascribed to the slow release of BF₃ rather than to the lithium cation.