Regioselectivity in the reduction of cyclic enediones with NaBH4/CeCl3
作者:Chunjian Liu、D.Jean Burnell
DOI:10.1016/s0040-4039(97)01498-6
日期:1997.9
Reductions of cyclic enediones by sodiumborohydride proceed with markedly different regiochemical preferences with and without cerium(III) chloride. In the presence of CeCl3, reductions appear to be controlled by two phenomena: the accessibility toward axial addition, in common with reactions without CeCl3, and accessibility for complexation by the Lewis acid.
Regio- and Stereoselectivity in the Reductions of Cyclic Enedione Systems
作者:Chunjian Liu、D. Jean Burnell
DOI:10.1021/jo962377m
日期:1997.5.1
Reductions of cyclic enedione substrates by NaBH4 and by LiAl(O-t-Bu)(3)H very predominantly gave monoreduction products with very high regio- and stereoselectivity. The reductions involved axial delivery of the hydride. The results indicated that electronic factors were dominated by steric considerations in the transition state of the reduction, even though the seemingly more encumbered carbonyl was reduced.