Synthesis of a Chiral Quaternary Carbon Center Bearing a Fluorine Atom: Enantio- and Diastereoselective Guanidine-Catalyzed Addition of Fluorocarbon Nucleophiles
The perfect combination: The title reaction provides adducts having quaternarycarboncentersbearing a fluorineatom with high ee and d.r. values (see scheme). The mechanism and origin of stereoselectivity were elucidated by DFT calculations. The bifunctional mode of the guanidine catalysis was demonstrated in the transition states resulting from the DFT results.
The strength of the weak: An L‐tert‐leucine‐derived amine–thioureacatalyst (see scheme, green box) promotes the asymmetric vinylogous conjugate addition reaction between γ‐aryl‐ and alkyl‐substituted butenolides with the butenamides and enoates shown. Computational studies show the preference for the observed stereochemistry is a result of favourable weak non‐bonding interactions, which stabilize
Synthesis of α-Stereogenic Amides and Ketones by Enantioselective Conjugate Addition of 1,4-Dicarbonyl But-2-enes
作者:Zhiyong Jiang、Yuanyong Yang、Yuanhang Pan、Yujun Zhao、Hongjun Liu、Choon-Hong Tan
DOI:10.1002/chem.200802601
日期:2009.5.4
Constructing α‐stereogenic amides and ketones: The highly regioselective and enantioselectiveconjugateaddition of 1,3‐dicarbonyl compounds to 1,4‐dicarbonyl but‐2‐enes has been developed with the chiral bicyclic guanidine as catalyst (ee values up to 97 %; see scheme).