SELECTIVE REDUCTION OF THE CARBONYL GROUP IN ORGANOMERCURIALS - A FACILE METHOD FOR THE PROTECTION-DEPROTECTION OF THE MERCURIO GROUP AND ANEW ROUTE TO ANNULATED LACTONES

Reduction of the carbonyl group in organomercurials can be carried out with retention of the mercury, provided it is protected by methylatio n. Thus, the bromomercurio aldehyde 6 is first methylated by MeCu to g ive 11, whose reduction with NaBH4, LiAlH(t-BuO)(3), L-Selectride(R), or superhydride(R) affords the alcohol 12. Mercury is then deprotected by treatment with HgBr2 (12 --> 13). The resulting alcohol 13 undergo es the palladium(II)-catalyzed carbonylation to produce the correspond ing lactone 15. Five- and six-membered lactones are readily accessible via this methodology. Copyright (C) 1996 Elsevier Science Ltd