Catalytic Desymmetrizing Dehydrogenation of 4-Substituted Cyclohexanones through Enamine Oxidation
作者:Lihui Zhu、Long Zhang、Sanzhong Luo
DOI:10.1002/anie.201713327
日期:2018.2.19
A desymmetrizing dehydrogenation process catalyzed by a chiral primary amine is described herein. The reaction proceeds through the oxidation of a ketone enamine by IBX and enables the highly enantioselective desymmetrization of 4‐substituted cyclohexanones with the generation of chiral 4‐substituted cyclohexenones containing a remote γ‐stereocenter.
the corresponding cyclohexenones 4 with a remote chiral all‐carbon quaternary center at the γ position is described. Chiral rhodium–bis(oxazolinyl)phenyl complexes 1 were effective catalysts for this transformation. This catalytic system was extended to the asymmetric transformation of spirocarbocyclic cyclohexadienones 5 to give the corresponding products 6 with highenantiomeric ratios.
A new method for chiral diamine-catalyzed Robinson-type annulation was developed to construct cyclohexenone derivatives bearing a quaternary carbon stereogenic center at the 4-position in high enantiomeric excess. This method was successfully applied to the short synthesis of (+)-sporochnol A.
Enantioselective Conversion of Achiral Cyclohexadienones to Chiral Cyclohexenones by Desymmetrization
作者:Yixin Han、Simon Breitler、Shao-Liang Zheng、E. J. Corey
DOI:10.1021/acs.orglett.6b03186
日期:2016.12.2
The enantioselective reduction of prochiral 4,4-disubstituted 2,5-cyclohexadienones to chiral 2-cyclohexenones has been accomplished by the use of a carefully selected chiral bisphosphine–CuI complex and diisobutylaluminum hydride–hexamethylphosphoric triamide complex. This reagent has provided access to a key bicyclic intermediate for the totalsynthesis of the natural enantiomer of the pentacyclic