We report here the silylation of α,β‐unsaturated acceptors in water at room temperature using a copper catalyst. A broad substrate scope, including chalcone derivatives, esters, nitrile, and dienones, has been explored. In all cases, the reaction proceeded well to give the desired products in good to excellent yield.
NHC–Cu-Catalyzed Silyl Conjugate Additions to Acyclic and Cyclic Dienones and Dienoates. Efficient Site-, Diastereo- and Enantioselective Synthesis of Carbonyl-Containing Allylsilanes
作者:Kang-sang Lee、Hao Wu、Fredrik Haeffner、Amir H. Hoveyda
DOI:10.1021/om300790t
日期:2012.11.26
Efficient and highlydiastereo- 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 coppercomplex of a chiral monodentate N-heterocyclic carbene; the requisite reagent, PhMe2Si–B(pin), is commercially available or can be easily prepared. Transformations
Direct Catalytic Asymmetric Doubly Vinylogous Michael Addition of α,β-Unsaturated γ-Butyrolactams to Dienones
作者:Xiaodong Gu、Tingting Guo、Yuanyuan Dai、Allegra Franchino、Jie Fei、Chuncheng Zou、Darren J. Dixon、Jinxing Ye
DOI:10.1002/anie.201504276
日期:2015.8.24
An asymmetricdoublyvinylogousMichaeladdition (DVMA) of α,β‐unsaturated γ‐butyrolactams to sterically congested β‐substituted cyclic dienones with high site‐, diastereo‐, and enantioselectivity has been achieved. An unprecedented DVMA/vinylogousMichaeladdition/isomerization cascade reaction affords chiral fused tricyclic γ‐lactams with four newly formed stereocenters.
Acicular purplish crystals were obtained from Cu(acac)(2) and a chiral bipyridine ligand. Although the crystals were not soluble, they nevertheless catalyzed asymmetric silyl conjugate addition of lip ophilic substrates in water. Indeed, the reactions proceeded efficiently only in water; they did not proceed well either in organic solvents or in mixed water/organic solvents in which the catalyst/substrates were soluble. This is in pronounced contrast to conventional organic reactions wherein the catalyst/substrates tend to be in solution. Several advantages of the chiral Cu(II) catalysis in water over previously reported catalyst systems have been demonstrated. Water is expected to play a prominent role in constructing and stabilizing sterically confined transition states and accelerating subsequent protonation to achieve high yields and enantioselectivities.