Highly Functionalized Cyclohexenyl Systems: Enzymatic Resolution and Selective Oxirane Opening Reactions of p-Benzoquinone Derivatives

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.