HYDROBORATION .93. CONVENIENT CONVERSION OF OPTICALLY PURE 2-ORGANYLAPOPINENES INTO THE (2-ORGANYLAPOISOPINYL)DIHALOBORANES POTENTIALLY VALUABLE FOR ASYMMETRIC-SYNTHESIS VIA CHIRAL ORGANOBORANES

Optically pure and sterically varied (2-organylapoisopinyl)dihaloboran es [RapBX(2), R = Me (except for X = I), Et, Pr, i-Bu, Ph, i-Pr, X = C l, Pr, I], potentially important reagents for asymmetric synthesis, ar e conveniently prepared by the in situ reduction and hydroboration rea ction of boron trihalide, trimethylsilane, and 2-organylapopinenes (2- R-apopinenes) under mild reaction conditions in essentially quantitati ve yield. Unfortunately, IpcBI(2) (RapBI(2), R = Me) could not be synt hesized by this procedure, although the more bulky 2-R-apopinenes prov ide the desired RapBI(2) derivatives.