ISOPINOCAMPHEYLHALOBORANE-METHYL SULFIDE AS HYDROBORATING AND STEREOSELECTIVE REDUCING AGENT

Reactions of alkenes and alkynes with the recently discovered isopinoc ampheylhaloborane-methyl sulfide (IpcBHX.SMe(2), X=Cl, Br, I) were inv estigated in detail in order to establish their usefulness as hydrobor ating agents. The reagents readily hydroborated alkenes at 50 degrees C and alkynes at 25 degrees C with excellent regioselectivity in placi ng the boron atom exclusively at the less hindered carbon atom. Especi ally, the selectivity achieved by the iodo derivative reaches essentia lly 100%. In addition to that, IpcBHX.SMe(2) was applied to the reduct ion of cyclic ketones to examine its stereoselectivity. The halogen su bstituent in these reagents plays an important role in the stereoselec tive reduction. The stereoselectivity increased dramatically with incr easing steric size of the substituent. Finally, the iodo derivative ac hieved highly stereoselective reduction, such selectivity being compar able to that previously achieved with trialkylborohydrides.