A ruthenium-catalyzed electrochemical dehydrogenative annulation reaction of aniline derivatives and alkynes has been developed for the synthesis of indoles. Electric current is used to recycle the active ruthenium-based catalyst and promote H2 evolution. The electrolysis reaction is operationally convenient as it employs a simple undivided cell, proceeds efficiently in an aqueous solution, and is
Recyclable [Ru2Cl3(p-cymene)2][PF6]/Cu(OAc)2/PEG-400/H2O system for oxidative annulation of alkynes by aniline derivatives: Green synthesis of indoles
作者:Yang Liao、Ting Wei、Tao Yan、Mingzhong Cai
DOI:10.1016/j.tet.2017.01.023
日期:2017.3
[Ru2Cl3(p-cymene)(2)][PF6] in a mixture of PEG-400 and water is shown to be a highly efficient catalyst for the oxidative annulation of alkynes by N-2-pyrimidyl-substituted anilines bearing a removable directing group. The reaction could be conducted at 100 degrees C using Cu(OAc)(2)center dot H2O (2.0 equiv) as oxidant, yielding a variety of indole derivatives in good to excellent yields. The isolation of the products was readily performed by extraction with petroleum ether and more importantly, both [Ru2Cl3(p-cymene)(2)][PF6] and Cu(OAc)(2) in PEG-400/H2O system could be easily recycled and reused six times without any loss of catalytic activity. (C) 2017 Elsevier Ltd. All rights reserved.