Cu−Catalyzed Enantioselective Conjugate Addition of Alkylzincs to Cyclic Nitroalkenes: Catalytic Asymmetric Synthesis of Cyclic α-Substituted Ketones
作者:Courtney A. Luchaco-Cullis、Amir H. Hoveyda
DOI:10.1021/ja020605q
日期:2002.7.1
highly enantioselective (>/=92% ee) catalytic method for conjugate addition of alkylzinc reagents to cyclic nitroalkenes is reported. Reactions are promoted in the presence of 0.5-5 mol % (CuOTf)2.C6H6 and 1-10 mol % of chiral amino acid-based phosphine ligands at 0 degrees C in toluene. The Cu-catalyzed reactions can be effectively carried out with small-, medium-, and large-ring nitroalkenes. Depending
enamide of a chiral iminederivedfrom a ketone and (S)-valinol or (S)-t-leucinol undergoes addition to 1-alkene to generate a gamma-zincioimine intermediate, which reacts with a carbon electrophile to give upon hydrolysis an optically active alpha-substituted ketone in good yield. The stereoselectivity of the addition reaction may reach 99% for the reaction of a cyclohexanoneimine with ethylene.
A strategy for the asymmetric synthesis of medium ring oxygen heterocycles: Enantioselective total synthesis of (+)-octahydrodeacetyldebromolaurencin
作者:J.Stephen Clark、Andrew B. Holmes
DOI:10.1016/s0040-4039(00)80490-6
日期:1988.1
Asymmetric Hydrovinylation of 1-Vinylcycloalkenes. Reagent Control of Regio- and Stereoselectivity
作者:Jordan P. Page、T. V. RajanBabu
DOI:10.1021/ja301640e
日期:2012.4.18
1-Vinylcycloalkenes undergo highly regio- and enantioselective (>98% ee) 1,4-hydrovinylation (HV) when treated with ethylene (1 aim) at room temperature in the presence of [(S,S)-2,4-bis-diphenylphosphinopentane (BDPP)]CoCl2 (0.05 equiv) and methylaluminoxane. The minor 1,2-HV products, seen only in 1-vinylcyclohexene (similar to 15%) and 1-vinylcycloheptene (2%), are formed as racemic mixtures. The corresponding Ni(II)-catalyzed HV reactions of these substrates give mostly the 1,2-adducts. Racemic 4-tert-butyl-1-vinylcyclohexene, when treated with Co[(S,S)-(BDPP)]Cl-2 and ethylene, undergoes a rare enantiodivergent reaction giving two diastereomers each in >98% cc.
TSUSHIMA, KAZUNORI;MURAI, AKIO, CHEM. LETT.,(1990) N, C. 761-764