of an amine was used to not only simplify the preparation of the catalysts but also increase Lewis acidity of the boron atom. The in situ generated borenium salts showed exceptional Lewis acidity and successfully catalyzed asymmetric Diels–Alderreactions of cyclopentadiene and dienophiles in excellent yields and enantioselectivities. The NMR studies of these oxathiaborolium structures were reported
The First General Enantioselective Catalytic Diels−Alder Reaction with Simple α,β-Unsaturated Ketones
作者:Alan B. Northrup、David W. C. MacMillan
DOI:10.1021/ja017641u
日期:2002.3.1
The first general approach to enantioselectivecatalysis of the Diels−Alderreaction with simple ketone dienophiles has been accomplished. The use of iminium catalysis has enabled enantioselective access to a fundamental Diels−Alderreaction variant that has previously been unavailable using chiral Lewis acid catalysis. A new chiral amine catalyst has been developed that allows a variety of monodentate
Broad-Spectrum Enantioselective Diels−Alder Catalysis by Chiral, Cationic Oxazaborolidines
作者:Do Hyun Ryu、Thomas W. Lee、E. J. Corey
DOI:10.1021/ja027468h
日期:2002.8.1
catalysts for Diels-Alder addition of cyclopentadiene to a wide variety of dienophiles. Adducts have been obtained in excellent yield and enantioselectivity from alpha,beta-unsaturated esters, lactones, and cyclic ketones. The absolute facial selectivity for each of these substrates follows a common pattern which differs from that observed with alpha,beta-enals. The different reaction channels can be