Copper‐Catalyzed Intramolecular C(sp³)H and C(sp²)H Amidation by Oxidative Cyclization

Abstract

The first copper-catalyzed intramolecular C(sp(3))-H and C(sp(2))-H oxidative amidation has been developed. Using a Cu(OAc)2 catalyst and an Ag2CO3 oxidant in dichloroethane solvent, C(sp(3))-H amidation proceeded at a terminal methyl group, as well as at the internal benzylic position of an alkyl chain. This reaction has a broad substrate scope, and various β-lactams were obtained in excellent yield, even on gram scale. Use of CuCl2 and Ag2CO3 under an O2 atmosphere in dimethyl sulfoxide, however, leads to 2-indolinone selectively by C(sp(2))-H amidation. Kinetic isotope effect (KIE) studies indicated that C-H bond activation is the rate-determining step. The 5-methoxyquinolyl directing group could be removed by oxidation.

Copper‐Mediated ortho‐Nitration of Arene and Heteroarene CH Bonds Assisted by an 8‐Aminoquinoline Directing Group

“…[21] In addition, copper-catalyzed intramolecular C(sp 3 ) À H and C(sp 2 ) À H amidation with an 8-aminoquinoline or picolinic acid group as the directing group was also developed by several groups. [22] Inspired by these reports, we were tempted to test the use of bidentate auxiliaries in the selective nitration of arenes. Herein we wish to disclose a copper-mediated, aminoquinoline group-assisted nitration of benzoic acid derivatives.…”

“…As depicted in Scheme 2, coordination of 1a to a copper(II) species followed by ligand exchange generates the copper complex 5; 5 next undergoes C À H activation to form the aryl/Cu(II) species 6 by a cyclocupration process. [22] Subsequently, the Cu(OAc) 2 -promoted oxidation of 6 affords a Cu(III) species 7.…”

Recent Advances in First‐Row‐Transition‐Metal‐Catalyzed Dehydrogenative Cou­pling of C(sp3)–H Bonds

“…At the same time, Kanai and co-workers independently developed this intramolecular amination reaction with Cu(OAc) 2 in the presence of an excess amount of Ag 2 CO 3 (Scheme 12). [22] Similar substrate scope and conversion yields to our work were described. Since Ag 2 CO 3 was employed as the oxidant, it is believed that the Cu(OAc) 2 is oxidized to a Cu III species before the C-H activation, and thus a Cu III /Cu I catalytic cycle was proposed for the amination process.…”

Copper-Mediated Intermolecular C–H/C–H and C–H/N–H Couplings via Aromatic C–H Cleavage

“…The intermolecular dehydrogenative cross-couplings mentioned in this chapter are such good examples, and they are otherwise challenging even under known noble transition metal catalysis. However, there is still a large room for further Scheme 3 A unique one-electron redox mechanism in Cu(II)-mediated C-H/O-H coupling Scheme 4 A condition-dependent, divergent mechanism in Cu(II)-mediated C-H activation: SET vs organometallic pathway development: improvement of turnover number (or frequency), use of atmospheric oxygen as an ideal terminal oxidant, activation of even more challenging sp 3 C-H bonds [83][84][85], and application to asymmetric catalysis. The clarification of detailed mechanisms and design of new Cu-based catalysis can address these problems and open a door to truly useful and practical synthetic transformation based on C-H activation chemistry.…”