Stereoselective denitrohydrogenation reactions of 4-alkyl-5-glyco-4-nitrocyclohex-1-enes
摘要:
The denitrohydrogenation of chiral 4-alkyl-5-glyco-4-nitrocyclohex-1-enes (1 and 3) with tri-n-butyltin hydride and azobisisobutironitrile proceeded in a completely stereoselective way. In each case. the hydrogen atom provided 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 perform denitroalkylation reactions of 1a, 3a or 8 with electron-deficient alkenes yielded only denitrohydrogenated products. (C) 2001 Elsevier Science Ltd. All rights reserved.
Michaeladditions of 5-glyco-4-nitrocyclohex-1-enes (2 and 3) proceeded in a stereoselective way, leading in each case to single adducts in which the electron-deficient alkenes add on the C-4 of the cyclohexene rings, in a trans mode to the adjacent, sterically demanding, sugar side-chain. When dimethyl maleate or dimethyl fumarate and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) were used, there was in