SYNTHESIS AND REACTIONS OF OPTICALLY PURE CYCLOHEXYL(O-METHOXYPHENYL)PHOSPHINE-BORANE AND T-BUTYL-(O-METHOXYPHENYL)PHOSPHINE-BORANE

Cyclohexyl(o-methoxyphenyl) menthyloxyphosphine-borane and t-butyl(o-methoxyphenyl)menthyl-oxyphosphine-borane were prepared from dichlorocyclohexylphosphine and t-butyldichlorophosphine by successive treatments with (-)-menthol, o-methoxyphenylmagnesium bromide, and borane-THF complex. The separated pure diastereomers of each of the compounds underwent reaction with lithium naphthalenide to afford optically pure cyclohexyl(o-methoxyphenyl)phosphine-borane and t-butyl(o-methoxyphenyl)phosphine-borane, respectively. These secondary phosphine-boranes reacted readily with various electrophiles in the presence of bases with virtually net retention of configuration. A new chiral phosphine ligand, (S,S)-1,2-bis[cyclohexyl(o-meth-oxyphenyl)phosphino]ethane was synthesized via the optically pure phosphine-boranes.