Enantioselective synthesis of unsymmetrical diaryl substituted spirocyclohexanonepyrazolones through a cascade [4+2] double Michael addition
串联[4+2]双迈克尔加成反应立体选择性的合成非对称性的螺【吡唑啉酮-环己酮】衍生物
Jin-Xin Zhang(张金鑫), Nai-Kai Li(李乃凯), Zhao-Min Liu(刘兆敏), Xiao-Fei Huang(黄晓飞), Zhi-Cong Geng(耿志聪) and Xing-Wang Wang(王兴旺)*
Adv. Synth. Catal. 2013, 355, 781-789.
The spirocyclic pyrazolones are an important class of molecular structures with significant biological and pharmaceutical activities. Herein, we demonstrate that the combination of a Cinchona-based chiral primary amine and an ortho-fluorobenzoic acid is an efficient catalyst system for the double Michael addition of arylidenepyrazolones with α,β-unsaturated ketones, providing chiral unsymmetrical 6,10-diaryl-substituted spiro[cyclohexanone-pyrazolone] derivatives in high yields (up to 98%) with good diastereoselectivities and excellent enantioselectivities (up to 88:12 dr, 99% ee).
