Transition-metal-free C(sp3)–H/C(sp3)–H dehydrogenative coupling of saturated heterocycles with N-benzyl imines

Zhengfen Liu; Minyan Li; Guogang Deng; Wanshi Wei; Ping Feng; Quanxing Zi; Tiantian Li; Hongbin Zhang; Xiaodong Yang; Patrick J. Walsh

doi:10.1039/D0SC00031K

Transition-metal-free C(sp³)–H/C(sp³)–H dehydrogenative coupling of saturated heterocycles with N-benzyl imines†

Zhengfen Liu,‡^a Minyan Li,‡*^b Guogang Deng,^a Wanshi Wei,^a Ping Feng,^a Quanxing Zi,^a Tiantian Li,^ac Hongbin Zhang,

*^a Xiaodong Yang

*^a and Patrick J. Walsh

*^b

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* Corresponding authors

^a Key Laboratory of Medicinal Chemistry for Natural Resources, Ministry of Education and Yunnan Province, State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, School of Chemical Science and Technology, Yunnan University, Kunming, P. R. China
E-mail: xdyang@ynu.edu.cn, zhanghb@ynu.edu.cn

^b Roy and Diana Vagelos Laboratories Penn/Merck Laboratory for High-Throughput Experimentation Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, PA, USA
E-mail: pwalsh@sas.upenn.edu, liminyan@sas.upenn.edu

^c Department of Soil and Water Science, University of Florida, 2181 McCarty Hall A, Gainesville, FL 32611-0290, USA

Abstract

A unique C(sp³)–H/C(sp³)–H dehydrocoupling of N-benzylimines with saturated heterocycles is described. Using super electron donor (SED) 2-azaallyl anions and aryl iodides as electron acceptors, single-electron-transfer (SET) generates an aryl radical. Hydrogen atom transfer (HAT) from saturated heterocycles or toluenes to the aryl radical generates alkyl radicals or benzylic radicals, respectively. The newly formed alkyl radicals and benzylic radicals couple with the 2-azaallyl radicals with formation of new C–C bonds. Experimental evidence supports the key hydrogen-abstraction by the aryl radical, which determines the chemoselectivity of the radical–radical coupling reaction. It is noteworthy that this procedure avoids the use of traditional strong oxidants and transition metals.

This article is part of the themed collection: Celebrating 10 years of Chemical Science

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Transition-metal-free C(sp³)–H/C(sp³)–H dehydrogenative coupling of saturated heterocycles with N-benzyl imines†

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