Recent Advances and Strategies for the Transition‐Metal‐Catalyzed C−H Functionalization of N‐Nitrosoanilines

Abstract

The challenges faced in the activation and functionalization of C−H bonds while producing high‐value aromatic intermediates are significant for synthetic organic chemistry. This review summarizes the advancements made toward the C−H functionalization of N‐nitrosoanilines in the past decade, in which the nitroso group coordinates to a transition metal, such as rhodium, palladium, cobalt, iridium, and ruthenium, acting as a directing group to allow the activation of the ortho C−H bond. The versatility of this synthetic approach has led to the regio‐ and chemoselective introduction of various functional groups giving rise to aromatic congeners with diverse functional and structural properties. C−H functionalized nitroso compounds can be further transformed into valuable synthetic intermediates and unique heterocyclic compounds. A description of the mechanism underlying each reaction is also included. This review includes the following sections:

Transition-metal catalyzed reactions of diazo compounds and N,N-dialkylnitrosoamines

“…5 Among these directing groups, N -nitrosoamino has proven to be particularly adept, known for its facile removal and versatility. 6 Highly regioselective insertions into ortho aromatic C(sp 2 )–H bonds of N -nitrosoanlines were achieved with a range of carbenes. 7 Recently, our group successfully developed a Rh( iii )-catalyzed ortho C–H functionalization of N -nitrosoanilines employing α-sulfonylcarbenes and naphthoquinone carbenes (Scheme 1b).…”

Cobalt-catalyzed C(sp3)–H bond functionalization to access indole derivatives

“…3 More recently, transition-metal catalyzed C–H bond functionalization as a powerful method to synthesize indoles has received tremendous attention because of its higher step- and atom-economy. 4 However, most of these elegant works focus on precious metal-based catalysts (Pd, Rh, Ru, etc . ), 5 and first-row transition metal-catalyzed C–H bond activation to construct indole derivatives, 6 especially for cobalt catalysts, has been reported very rarely.…”

Expeditious Synthesis of Spiroindoline Derivatives via Tandem C(sp2)–H and C(sp3)–H Bond Functionalization of N-Methyl-N-nitrosoanilines

“…In recent years, significant advances in overcoming this challenge have been made by seeking the assistance of directing groups (DGs) to guarantee proximity-driven regioselectivity and chelation-facilitated reactivity. In this regard, the nitroso group in N -nitrosoanilines has emerged as an outstanding DG for CHA reactions since it can not only be conveniently introduced and uninstalled but also readily coordinates with TM catalysts to assist the cleavage of the proximal C­(sp 2 )–H bonds. , In this regard, Zhu et al developed an effective method for the preparation of functionalized indole derivatives by using N -methyl- N -nitrosoaniline as a C2N1 synthon to undergo formal [3+2] annulation with α-diazo-β-keto compounds (Scheme a)…”

“…Based on the results obtained herein and those reported previously, a plausible pathway accounting for the formation of 3aa was proposed in Scheme . Initially, Rh­(III)-catalyzed and nitroso-group-assisted ortho -C–H bond metalation occurs with 1a to furnish five-membered rhodacycle species I .…”