cenbs of MoleWlu mid MacXomobculu shodi Polii A&y of Scioncsq Sic&i-I 12.90363 iAdz!, Polsnd B Reactions of (@+ch1orovinyl)methylpbenylphosphii oxide with aryl and alkenyl Chignard magents result in highly ste~~~~lsctivo dimsnt of the habvinyl gmup and affold virtually eMntiomWically pure aIylmethylpbmyl md alkenylmethylphcnylpbmphina oxi&es of inverted conflgumtion at phosphorus. Since the pioneering work of Mialow and wworkers~ and Nudelman and Cram,3 on stamoaelective reactions of Wmeric mcntbyl phospbinatcs with Grignard reagents (e.g. Equation l), synthetic routes to salemid P-chiral phospbine oxides and other P-chiral phosphine derivatives based on n~~leopbilic displacement reactions of P-resolved phosphorus esters with organomctallic reagents have athnctcd much attention.~ Yet, despite theii continued practical importance and development,5 syntheses in which virtually complete stereoselectivity in the displeccment stops can be accompli&d are still ran and not easily predictable. As noted early by Mislow2 and later experienced by others,6 such displaccmcnts art very sensitive to variation of groups at phosphorus and magnesium as well as to the nature of the ester leaving group. Recent diswvcries that halovinyl groups at sulfur '9 and at phosphorus9 can act as effective leaving groups for substition by Grignard reagents (Equations 2 and 3) turned our attention to the possibility of probing utility of these groups for the stereoselective synthesis of scalemic phosphine oxides. It could be