Evaluating aryl esters as bench-stable C(1)-ammonium enolate precursors in catalytic, enantioselective Michael addition–lactonisations
作者:Claire M. Young、James E. Taylor、Andrew D. Smith
DOI:10.1039/c9ob00703b
日期:——
An evaluation of a range of aryl, alkyl and vinyl esters as prospective C(1)-ammonium enolate precursors in enantioselective Michael addition–lactonisation processes with (E)-trifluoromethylenones using isothiourea catalysis is reported. Electron deficient aryl esters are required for reactivity, with 2,4,6-trichlorophenyl esters providing optimal product yields. Catalyst screening showed that tetramisole
的范围内的芳基,烷基和乙烯基酯作为预期C(1) -铵烯醇化物的前体与对映选择性迈克尔加成-内酯化过程的评价(Ë报道了使用异硫脲催化的)-三氟甲基烯酮。缺乏电子的芳基酯对于反应是必需的,而2,4,6-三氯苯基酯可提供最佳的产品收率。催化剂筛选显示,四咪唑是最有效的异硫脲催化剂,以优异的收率和立体选择性(高达90:10 dr和98:2 er)提供了所需的二氢吡喃酮产物。已评估了该方法的范围和局限性,在用MeOH开环后生成了一系列二酯产物,从而得到具有优异立体控制性的立体定义的二氢吡喃酮(10个实例,通常约90:10 dr和> 95:5 er)。