在无溶剂反应条件下(SFRC),在各种温度(20-80°C)下,将N-卤代琥珀酰亚胺卤代数个芳基取代的酮,环酮,1,3-二酮和β-酮酰胺,而较少烯醇化的酮则需要存在酸催化剂(对甲苯磺酸,PTSA)。取代的苯乙酮的溴化反应遵循一级动力学v = k Br [酮],并与酮-烯醇平衡常数具有以下相关性:log k Br = 0.3p K E + C 1,少酚化的底物更具反应性;在速率确定步骤中产生的适度正电荷已通过Hammett相关性得到证实(ρ = -0.5)。另一方面,在环状酮中观察到相反的关系:log k Br = -0.6p K E + C 2,表明具有较高烯醇化常数(K E)的底物具有较高的反应性。发现在SFRC溴化之前,溶剂(MeCN,MeOH)的性质在酮-NBS-PTSA混合物的预组织中起着重要作用。
Unified Strategy for Iodine(III)-Mediated Halogenation and Azidation of 1,3-Dicarbonyl Compounds
作者:Marc J. Galligan、Ramulu Akula、Hasim Ibrahim
DOI:10.1021/ol403504z
日期:2014.1.17
A mild and rapid (diacetoxyiodo)benzene-mediated formal electrophilic alpha-azidation of 1,3-dicarbonyl compounds using commercially available Bu4NN3 as the azide source is reported. The reaction conditions employed are based on optimization studies conducted on the analogous halogenations with Et4NX (X = Cl, Br, 1).