Acceleration of Enantioselective Cycloadditions Catalyzed by Second-Generation Chiral Oxazaborolidinium Triflimidates by Biscoordinating Lewis Acids
作者:Barla Thirupathi、Simon Breitler、Karla Mahender Reddy、E. J. Corey
DOI:10.1021/jacs.6b08018
日期:2016.8.31
oxazaborolidines by the strong acid triflimide (Tf2NH) in CH2Cl2 solution leads to highly active chiralLewis acids that are very effective catalysts for (4 + 2) cycloaddition. We report herein that this catalytic activity can be further enhanced by the use of Tf2NH in combination with the biscoordinating Lewis acid TiCl4 or SnCl4 as a coactivator. The effective increase in acidity of an exceedingly strong