作者:David M. Heathcote、Gareth A. De Boos、John H. Atherton、Michael I. Page
DOI:10.1039/a707946j
日期:——
The hydrolysis of coumaran-2-one and 5-substituted 3-phenylcoumaran-2-ones is preceded by a pre-equilibrium involving the formation of an enolate anion at high pH. The pKa of 3-phenylcoumaran-2-one is 8.39 in water at 25 °C and the 3-phenyl substituent increases the carbon acidity by 104. However, despite this ready carbanion formation, the conventional addition–elimination mechanism for hydrolysis
香豆素-2-酮和5-取代的3-苯基香豆素-2-酮的水解之前是涉及高pH下烯醇酸根阴离子形成的预平衡。3-苯基库马兰-2-酮的p K a在25°C的水中为8.39,并且3-苯基取代基使碳酸度提高10 4。然而,尽管这个准备形成负碳离子,对于3- phenylcoumaran -2-酮水解的常规加成-消除机构由0.63溶剂动力学同位素效应和布朗斯台德证实β 1克-0.6。这与四面体中间体的速率限制形成相容。