Abstract
Four catalysts based on new amides of chiral 1,2-diamines and 2-sulfobenzoic acid have been developed. The alkali-metal salts of these betaine-like amides are able to form imines with enones, which are activated by Lewis acid interaction for nucleophilic attack by 4-hydroxycoumarin. The addition of 4-hydroxycoumarin to enones gives ee’s up to 83% and almost quantitative yields in many cases. This novel type of catalysis provides an effective alternative to conventional primary amino catalysis were strong acid additives are essential components.
Highlights
Organocatalysis based on primary or secondary amines enables a myriad of enantioselective transformations, e.g., with aromatic or aliphatic enones [1]
We report the development of new catalysts based on chiral 1,2diamines and present their application in the asymmetric addition of 4-hydroxycoumarin (1) to prochiral α,β-unsaturated ketones
The idea was to choose a Lewis acid that is strong enough to activate the imine preformed by the catalyst and the Michael system, so that the nucleophilic attack shown in Scheme 1 occurs
Summary
Organocatalysis based on primary or secondary amines enables a myriad of enantioselective transformations, e.g., with aromatic or aliphatic enones [1]. There are many approaches employing protonated derivatives of chinchona alkaloids [2,3,4,5], amino acid derivatives, and chiral 1,2-diamines, which provide excellent yields and enantioselectivities. The newly developed catalysts are derived from C2-symmetric chiral diamines 2 and 3 and 2-sulfobenzoic acid by formation of a carboxylic amide (Scheme 3).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
