Department of Chemistry, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
J Am Chem Soc. 2015 Jan 21;137(2):616-9. doi: 10.1021/ja511889y. Epub 2015 Jan 13.
A small-ring phosphacycle is found to catalyze the deoxygenative condensation of α-keto esters and carboxylic acids. The reaction provides a chemoselective catalytic synthesis of α-acyloxy ester products with good functional group compatibility. Based on both stoichiometric and catalytic mechanistic experiments, the reaction is proposed to proceed via catalytic P(III)/P(V)═O cycling. The importance of ring strain in the phosphacyclic catalyst is substantiated by an observed temperature-dependent product selectivity effect. The results point to an inherent distinction in design criteria for organophosphorus-based catalysts operating via P(III)/P(V)═O redox cycling as opposed to Lewis base (nucleophilic) catalysis.
一种小环膦环被发现能够催化α-酮酯和羧酸的去氧缩合反应。该反应提供了一种具有良好官能团相容性的α-烷氧基酯产物的化学选择性催化合成方法。基于计量和催化机理实验，该反应被提出通过催化 P(III)/P(V)=O 循环进行。通过观察到与温度有关的产物选择性效应，证实了在磷环催化剂中环张力的重要性。这些结果表明，通过 P(III)/P(V)=O 氧化还原循环而不是路易斯碱（亲核）催化作用的有机磷基催化剂的设计标准存在内在区别。
