Highly Functionalized Cyclohexenyl Systems: Enzymatic Resolution and Selective Oxirane Opening Reactions of p-Benzoquinone Derivatives
journal contributionposted on 27.06.1998, 00:00 by Jeffrey T. Kohrt, Jian-Xin Gu, Carl R. Johnson
Diol 2, derived in two steps from p-benzoquinone, was converted to epoxy alcohol 3. The latter was resolved with crude Candida rugosa lipase in isopropenyl acetate/toluene to give acetate (−)-4 and residual alcohol (+)-3. Oxirane ring opening reactions of 3 and the corresponding acetate and TBDMS derivatives with a variety of nucleophiles gave diastereomerically pure 3,4,5,6-tetrasubstituted cyclohexene derivatives of type 6. X-ray crystal structures were obtained on compounds 6e, 6m and the diacetate prepared from 6l. Nitrogen nucleophiles provided entry in various aziridines 10. Pd(0)-catalyzed nucleophilic additions to substrate 5 cleanly provided the diastereomeric pattern of type 11. trans-5,6-Disubstituted cyclohexadienes 13 were obtained by an unusual syn-reductive elimination on bromocarbonates 12 utilizing Pd or Zn.