Stereoselective denitrohydrogenation reactions of 4-alkyl-5-glyco-4-nitrocyclohex-1-enes

The denitrohydrogenation of chiral 4-alkyl-5-glyco-4-nitrocyclohex-1-enes ( 1 and 3) with tri-n-butyltin hydride and azobisisobutironitrile proceeded i n a completely stereoselective way. In each case. the hydrogen atom provide d by tri-n-butyltin hydride adds to a free radical intermediate in a trans mode to the adjacent, sterically demanding, sugar side-chain. Attempts to p erform denitroalkylation reactions of 1a, 3a or 8 with electron-deficient a lkenes yielded only denitrohydrogenated products. (C) 2001 Elsevier Science Ltd. All rights reserved.