Oxaphosphetane versus betaine formation in epoxide ring opening by PPh3: a mechanistic probe by ab initio and DFT modeling

Ab initio and density functional investigations on the deoxygenation of cis-2,3-dimethylepoxide by PPh3 reveal a two-step mechanism. Simultaneous ring-opening and C–C bond rotation facilitates oxaphosphetane formation thereby ruling out the formation of a betaine intermediate and is consistent with the inversion of stereochemistry observed in the reaction.