THE NUCLEOPHILIC DISPLACEMENT ROUTE TO HOMOCHIRAL ARYLPHOSPHINE OXIDES

Article abstract of DOI:10.1016/S0040-4020(01)85600-3

The stereoisomerically pure oxazaphospholidine formed by reaction of (1R,2S)-ephedrine with PhPCl2 is oxidised by Bu^tOOH to the corresponding P-oxide, shown to have R-stereochemistry at phosphorus by X-ray analysis.The product reacts regio- and stereospecifically with o-anisylmagnesium bromide to give the product formed by P-O fission with retention of configuration, which was also characterised by X-ray diffraction.The ephedrine residue was replaced by O-methyl under acid catalysis with inversion of configuration.Attempts to incorporate p-fluorophenyl using similar conditions led to isolation of the pyrophosphinate in low yield.The OMe residue in the methoxyphosphinate was readily displaced by aliphatic or aromatic Grignard reagents giving the corresponding phosphine oxides with inversion of configuration.This procedure constitutes a simple route to di- and triarylphosphine oxides in ca. 95percent e.e.; optical purities were estimated by NMR methods.