Hydrated ferric sulfate-catalyzed reactions of indole with aldehydes, ketones, cyclic ketones, and chromanones: Synthesis of bisindoles and trisindoles
作者:Wayland E. Noland、Honnaiah Vijay Kumar、Grant C. Flick、Cole L. Aspros、Jong Hyeon Yoon、Andre C. Wilt、Nasim Dehkordi、Sheng Thao、Andrew K. Schneerer、Siming Gao、Kenneth J. Tritch
DOI:10.1016/j.tet.2017.05.061
日期:2017.7
Hydrated ferric sulfate [Fe2(SO4)3·xH2O] has been found to be an efficient catalyst for condensation of bisindoles or trisindoles with aliphatic or aryl aldehydes and ketones including methyl and ethyl-alkyl ketones, methyl aryl ketones, cyclic ketones, and 4-chromanones in 19–96% yields. Trisindoles and 2,2'-alkylidenebisindoles were obtained from indole-3-carbaldehydes or 3-methylindole in 72–84% yields
水合硫酸铁[Fe 2(SO 4)3 · x H 2 O]被发现是双吲哚或三吲哚与脂族或芳基醛和酮(包括甲基和乙基烷基酮,甲基芳基酮)缩合的有效催化剂,环酮和4-chromanones的产率为19-96%。从吲哚-3-甲醛或3-甲基吲哚获得三吲哚和2,2'-亚烷基双吲哚,产率为72–84%。总共使用了43种底物,得到33种双吲哚,3种三吲哚和一种2:2产物。其中有十七个是新的。用Fe 2(SO 4)3 · x加热乙醇悬浮液可获得最佳结果。H 2 O负载量为60 mg / mmol亲电试剂。反应时间通常为1-4小时,而受阻亲电试剂则需要8-24小时。这些条件足够强以促进吲哚与底物的2:1缩合,而不会形成高阶副产物,几乎没有例外。该策略的特征在于催化剂对各种官能团的耐受性,易于获得的起始原料,简单的操作,温和的反应条件以及对环境友好。