Cyclisation reactions involving the oxidation of carboxylic acids with lead tetra-acetate. Part I. The conversion of 2′-substituted biphenyl-2-carboxylic acids into 3,4-benzocoumarin
作者:D. I. Davies、C. Waring
DOI:10.1039/j39670001639
日期:——
The reaction of 2′-substituted biphenyl-2-carboxylic acids (where the 2′-substituent is H, CO2H, NO2, Cl, OMe, or CO2Me) with lead tetra-acetate in refluxing benzene solution, under a nitrogen atmosphere, affords 3,4-benzocoumarin as a major organic product. Only a trace is formed when the 2′-substituent is Me. o-Terphenyl-2-carboxylic acid gives no 3,4-benzocoumarin, but triphenylene is formed in
在回流的苯溶液中,2'-取代的联苯-2-羧酸(2'-取代基为H,CO 2 H,NO 2,Cl,OMe或CO 2 Me)与四乙酸铅在回流的苯溶液中在氮气气氛下,提供3,4-苯并香豆素为主要有机产物。当2'-取代基为Me时,仅形成痕迹。邻-叔苯基-2-羧酸不产生3,4-苯并香豆素,但是以高收率形成三亚苯基。建议这些环化反应涉及自由基,特别是AS的中间体。苯溶液中由2'-取代的联苯-2-羧酸衍生的二酰基过氧化物的热分解产物与在2'-取代的联苯-2-羧酸上形成的产物相似。酸与四乙酸铅反应。