THE SYNTHESIS OF OPTICALLY-ACTIVE P-PHENYL-P-(2,4,6-TRIMETHYLPHENYL)PHOSPHINAMIDE AND AN X-RAY STRUCTURE OF (-)-(1R)-N-(1-PHENYLETHYL)(SP)-P-PHENYL-P-(2,4,6-TRIMETHYLPHENYL)PHOSPHINAMIDE

The primary phosphinic amide P-phenyl-P-(2,4,6-trimethylphenyl)phosphinamide has been prepared in optically active form (75% enantiomeric excess) in six steps from dichlorophenylphosphine. The configuration of the intermediate N-(1-phenylethyl)-P-phenyl-P-(2,4,6-trimethylphenyl)phosphinamide has been established by an X-ray crystal structure determination of the minor diastereoisomer. This compound exhibits in the solid state two independent rotameric conformations about the P-N bond. Geometry optimisation by MNDO MO calculations refined these to the same rotamer having the nitrogen lone pair anticlinal to the P-O bond.