Intramolecular Base-Free Catalytic Wittig Reaction: Synthesis of Benzoxepinones

Article abstract of DOI:10.1021/acs.joc.8b02789

A straightforward two-step synthesis of benzoxepinones was developed via base-free phosphane-catalyzed Wittig reaction. 3-Methyl-1-phenyl-2-phospholene 1-oxide was used as a precatalyst and trimethoxysilane as a reducing agent. Additionally benzoic acid is employed as a catalyst to facilitate the reduction of the phosphane oxide. Mechanistic investigation revealed the formation of a coumarin as a side product, which was identified by 2D NMR experiments. First results of metabolic activity tests on the prepared benzoxepinones are reported.