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NHC–Cu-Catalyzed Silyl Conjugate Additions to Acyclic and Cyclic Dienones and Dienoates. Efficient Site-, Diastereo- and Enantioselective Synthesis of Carbonyl-Containing Allylsilanes

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journal contribution
posted on 26.11.2012, 00:00 by Kang-sang Lee, Hao Wu, Fredrik Haeffner, Amir H. Hoveyda
Efficient and highly diastereo- and enantioselective conjugate additions of phenyldimethylsilyl units to acyclic and cyclic dienones and dienoates are disclosed. The C–Si bond forming reactions are catalyzed by 2.0–2.5 mol % of a copper complex of a chiral monodentate N-heterocyclic carbene; the requisite reagent, PhMe2Si–B­(pin), is commercially available or can be easily prepared. Transformations generate allylsilanes in up to 98% yield and >99:1 enantiomeric ratio and proceed with complete 1,4-selectivity, unless the dienone or dienoate carries a trisubstituted alkene conjugated to the carbonyl group; in the latter cases, 1,6-addition products are obtained exclusively and in up to >98% Z selectivity.

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