Influence of electronic and steric factors on 2,3-dihydroimidazo [1,2-a]pyridine-based enantioselective acylation catalysts

The catalytic activity and enantioselectivity of chiral 2,3-dihydroimidazo[1,2-a]pyridine (DHIP) derivatives was examined as a function of the steric environment of the nucleophific nitrogen and the electronic properties of the pyridine ring. 2-Phenyl-6-trifluoroinethyl-DHIP (CF3-PIP) was confirmed to be the best catalyst in this series. In addition, three second-generation catalysts derived from the 1,2dihydroimidazo[1,2-a]quinoline (DHIQ) core were tested and proved to be considerably more active than CF3-PIP. (c) 2005 Elsevier Ltd. All rights reserved.