Evaluation of Catalyst Acidity and Substrate Electronic Effects in a Hydrogen Bond-Catalyzed Enantioselective Reaction
作者:Katrina H. Jensen、Matthew S. Sigman
DOI:10.1021/jo1013806
日期:2010.11.5
A modular catalyst structure was applied to evaluate the effects of catalystacidity in a hydrogen bond-catalyzed hetero Diels−Alder reaction. Linear free energy relationships between catalystacidity and both rate and enantioselectivity were observed, where greater catalystacidity leads to increased activity and enantioselectivity. A relationship between reactant electronic nature and rate was also
The present invention relates to a process for stereoselective cycloaddition reactions which generally comprises a cycloaddition reaction between a pair of substrates, each either chiral or prochiral, that contain reactive &pgr;-systems, in the presence of a non-racemic chiral catalyst, to produce a stereoisomerically enriched product. The present invention also relates to novel asymmetric catalyst complexes comprising a metal and an asymmetric tridentate ligand.
[reaction: see text] A BINOLate-zinc complex prepared in situ from Et(2)Zn and 3,3'-dibromo-1,1'-bi-2-naphthol (3,3'-Br(2)-BINOL) was found to be a highly efficient catalyst for the enantioselective hetero-Diels-Alder reaction of Danishefsky's diene and aldehydes to give 2-substituted 2,3-dihydro-4H-pyran-4-one in up to quantitative yield and 98% ee.
A stable chiral (acyloxy)borane (CAB) complex is prepared in situ by mixing a tartaric acid derivative and arylboronic acids at room temperature. A solution of the catalyst is effective in catalyzing hetero Diels-Alderreactions to produce dihydropyrone derivatives of high optical purities.
Chiral Chromium(III) Porphyrins as Highly Enantioselective Catalysts for Hetero-Diels–Alder Reactions Between Aldehydes and Dienes
作者:Albrecht Berkessel、Erkan Ertürk、Cécile Laporte
DOI:10.1002/adsc.200505249
日期:2006.1
tetrafluoroborate. These hitherto unknown chiral chromium porphyrins are efficient and highly enantioselective catalysts for the hetero-Diels–Alderreaction of aliphatic, aromatic, and heteroaromatic aldehydes with dienes of varying electron density. In the case of 1-methoxy-3-(trimethylsilyloxy)butadiene (“Danishefsky's diene”), enantiomeric excesses >90% were achieved in a number of cases, with furfural