Allylic Substitution for Construction of a Chiral Quaternary Carbon Possessing an Aryl Group
作者:Chao Feng、Yuichi Kobayashi
DOI:10.1021/jo400248y
日期:2013.4.19
Phenylcopper reagents derived from 2:1 PhMgBr/Cu(acac)(2) and 3:1:1 PhMgBr/Cu(acac)(2)/ZnI2 were found to be highly reactive and regioselective in the allylic substitution of gamma,gamma-disubstituted secondary allylic picolinates designed for construction of a quaternary carbon, whereas the previous 2:1 ArMgBr/CuBr center dot Me2S reagent and that with ZnX2 were unsuccessful. The generality of the ArMgBr/Cu(acac)(2) reagent was examined with enantiomerically enriched allylic picolinates, which furnished quaternary carbons with high efficiency in >92% regioselectivity and >97% chirality transfer. Two cyclohexanes with a quaternary carbon were synthesized by using these reagents.
Acyclic Stereocontrol in the Ireland–Claisen Rearrangement of α-Branched Esters
作者:Ying-chuan Qin、Craig. E. Stivala、Armen Zakarian
DOI:10.1002/anie.200702142
日期:2007.10.1
Highly Stereoselective C–C Bond Formation by Rhodium-Catalyzed Tandem Ylide Formation/[2,3]-Sigmatropic Rearrangement between Donor/Acceptor Carbenoids and Chiral Allylic Alcohols
作者:Zhanjie Li、Brendan T. Parr、Huw M. L. Davies
DOI:10.1021/ja303023n
日期:2012.7.4
The tandem ylide formation/[2,3]-sigmatropic rearrangement between donor/acceptor rhodium carbenoids and chiral allyl alcohols is a convergent C-Cbond forming process, which generates two vicinal stereogenic centers. Any of the four possible stereoisomers can be selectively synthesized by appropriate combination of the chiral catalyst Rh(2)(DOSP)(4) and the chiral alcohol.