Tunable Titanocene Lewis Acid Catalysts for Selective Friedel-Crafts Reaction of Indoles and<i>N</i>-Sulfonylaldimines
作者:Wang Xiu、Wang Zhenhua、Guofang Zhang、Weiqiang Zhang、Ya Wu、Ziwei Gao
DOI:10.1002/ejoc.201501122
日期:2016.1
enhanced the activity of the titanocene catalyst and promoted the synthesis of bisindole with excellent yields (98 %). The new organometallic Lewis acid catalysts are air-tolerant, can be used with low catalyst loading (3 mmol-%) and are compatible with –NO2, –F, –Cl, –Br, and –OMe (30 examples with yields from good to excellent). The titanocene catalysts were fully characterized by NMR and HRMS analysis
开发了一种在温和条件下控制吲哚和亚胺选择性 Friedel-Crafts 反应的新策略。苯酚衍生物被确定为有效的配体来微调二氯化钛的活性。Cp2TiCl2和苯酚以良好的产率(91%)催化吲哚和N-磺酰醛亚胺的单-Friedel-Crafts反应,而邻氨基苯酚显着提高了二茂钛催化剂的活性并促进了双吲哚的合成,产率高达98% )。新的有机金属路易斯酸催化剂具有空气耐受性,可在低催化剂负载量 (3 mmol-%) 下使用,并与 –NO2、–F、–Cl、–Br 和 –OMe(30 个示例,产率良好)相容优秀)。通过NMR和HRMS分析对二茂钛催化剂进行了充分表征。结果表明,Cp2TiCl(OC6H5) (I) 和 Cp2TiCl(OC6H4NH3+Cl–) (II) 分别是单和双Friedel-Crafts 反应的催化物质。与单官能酸催化剂 I 不同,催化剂 II 表现出两种酸组分的催化协同作用,