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Chiral Anion Directed Asymmetric Carbocation‐Catalyzed Diels–Alder Reactions
Author(s) -
Ni Shengjun,
Ramesh Naidu Veluru,
Franzén Johan
Publication year - 2016
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201501621
Subject(s) - carbocation , chemistry , catalysis , lewis acids and bases , amide , lewis acid catalysis , sulfuryl chloride , organic chemistry , medicinal chemistry
In recent years the carbocation has re‐emerged as a highly efficient Lewis acid catalyst for a variety of organic transformations. However, the goal of asymmetric carbocation catalysis has so far been out of reach mainly as a result of difficulties associated with the preparation of stable chiral carbocations. Here, we describe developments towards asymmetric carbocation catalysis based on the concept of chiral‐anion‐directed catalysis. Chiral tritylium salts can be conveniently prepared in situ by mixing trityl chloride derivatives with chiral phosphonate, phosphoramide, bis(sulfonyl)amide, and bis(sulfuryl)amide silver or sodium salts. It is shown that the bis(sulfuryl)amide/tritylium ion salt catalyzes the Diels–Alder reaction with an up to 53 % enantiomeric excess.