A copper-catalyzedasymmetricallylicsubstitution of γ,γ-disubstituted allylphosphates with arylboronates has been developed for the construction of quaternary stereocenters. High regio- and enantioselectivities have been achieved by employing a hydroxy-bearing chiral N-heterocyclic carbene ligand, and both E and Z substrates provide the same enantiomer as the major product. The mechanistic aspect
Copper-Catalyzed Enantioselective Allylic Substitution with Readily Accessible Carbonyl- and Acetal-Containing Vinylboron Reagents
作者:Fang Gao、James L. Carr、Amir H. Hoveyda
DOI:10.1002/anie.201202856
日期:2012.7.2
More with boron: The title reaction was developed to generate quaternary carbon stereogenic centers through the use of commercially available vinylboronreagents (see scheme, MOM=methoxymethyl, NHC=N‐heterocyclic carbene, pin=pinacolato). Application of the method to the two isomeric forms of an intermediate in morphine biosynthesis demonstrates its utility.
MOre with boron:标题反应是通过使用市售的乙烯基硼试剂(见方案,MOM=甲氧基甲基,NHC=N-杂环卡宾,pin=频哪醇)开发的,以生成季碳立体中心。将该方法应用于吗啡生物合成中中间体的两种异构形式证明了其效用。
Site- and Enantioselective Formation of Allene-Bearing Tertiary or Quaternary Carbon Stereogenic Centers through NHC–Cu-Catalyzed Allylic Substitution
作者:Byunghyuck Jung、Amir H. Hoveyda
DOI:10.1021/ja211269w
日期:2012.1.25
Catalyticenantioselective allylic substitutions that result in addition of an allenyl group (<2% propargyl addition) and formation of tertiary or quaternary C-C bonds are described. Commercially available allenylboronic acid pinacol ester is used. Reactions are promoted by a 5.0-10 mol % loading of sulfonate-bearing chiral bidentate N-heterocyclic carbene (NHC) complexes of copper, which exhibit the
Enantioselective Synthesis of Alkyne-Substituted Quaternary Carbon Stereogenic Centers through NHC−Cu-Catalyzed Allylic Substitution Reactions with (<i>i</i>-Bu)<sub>2</sub>(Alkynyl)aluminum Reagents
作者:Jennifer A. Dabrowski、Fang Gao、Amir H. Hoveyda
DOI:10.1021/ja2010829
日期:2011.4.6
A catalyticenantioselective method for the formation of alkyne-substituted all-carbon quaternary stereogenic centers is reported. Additions of alkynylaluminums to alkyl-, aryl-, carboxylic ester-, or silyl-substituted allylic phosphates are promoted by 1.0-5.0 mol % loadings of NHC-Cu complexes derived from air-stable and commercially available CuCl(2)·2H(2)O. The requisite Al-based reagents are prepared