Documentation of a rare example of an intramolecular 1,2-addition of a trialkylborane to a carbonyl group

In the course of synthetic studies aimed at the elaboration of highly funti onalized ketone 1, we observed what appeared to be an extremely rare exampl e of the addition of a trialkylborane to a carbonyl group. We were able to confirm the initial spectroscopic structural assignment by X-ray crystallog raphy. Some preliminary mechanistic experiments suggest that the addition o ccurs directly in the absence of oxygen prior to oxidation of the trialkylb orane during workup. (C) 2000 Elsevier Science Ltd. All rights reserved.