Rh-Catalyzed Cascade C–C/C_olefin–H Activations and Mechanistic Insight

Abstract

A reverse concerted metalation–deprotonation (CMD) process has been proposed as a key step to rationalize our newly discovered Rh-catalyzed C–C/Colefin–H cascade reaction to access 1-benzazepines. The reaction features redox-neutral conditions with 100% atom economy and showed broad substrate scope and good efficiency (23 examples, up to 85% yield). DFT calculations indicated that the reverse CMD process is a key step to kinetically override the normal “cut and sew” process and rendered the sequential olefinic C–H activation/reductive elimination as the predominant pathway.

Rhodium(III) Iodide Catalyzed Carboamination of Alkynes through C–N Bond Activation

“…Based on the control experiments and our group’s previous results with Rh catalysis, 9 10 we tentatively propose the reaction mechanism shown in Scheme 3 . C–N bond activation is catalyzed by RhI 3 by a concerted ligand-to-ligand exchange to form a N–Rh(III) bond and 3-iodo-2-methylprop-1-ene.…”

Type I [4σ+4π] versus [4σ+4π−1] Cycloaddition To Access Medium‐Sized Carbocycles and Discovery of a Liver X Receptor β‐Selective Ligand

“…First, the kinetically favored C 1 -C 8 rhodaindanone may undergo type II cycloaddition or participate in the cascade CÀ H activation, leading to interrupted "cut and sew" side products. [21] Second, a normal [4 + 2] annulation may occur, leading to 6-5-6 tricycle. [22] Third, decarbonylation could be an inevitable process against entropy loss during medium-sized ring formation.…”

Synthesis of Tetrahydro-indolones through Rh(III)-Catalyzed [3 + 2] Annulation of Enaminones with Iodonium Ylides

“…In particular, the Rh­(III)-catalyzed C­(sp 2 )–H bond functionalization/annulation of enaminones has been greatly developed in recent years, making quick and efficient access to multisubstituted aromatic/heterocyclic rings, including polycyclic aromatic compounds, isocoumarins, benzo­[ de ]­chromenes, and others . Nevertheless, to the best of our knowledge, these major advances in Rh­(III)-catalyzed annulation of enaminones focused on the C­(sp 2 )–H bond functionalization process occurring only on aryl ortho -carbon, and the C­(sp 2 )–H bond functionalization process on the alkenyl fragment of enaminones remains challenging, probably as a result of the strong π-coordinating ability of the CC bond having some inhibitory effect on the C–H bond activation process of the catalyst and the alkenyl C–H activation being more sensitive to steric hindrance . As a continuation of the development in Rh­(III)-catalyzed C–H activation of iodonium ylides and our work on developing enaminone chemistry for heterocycle synthesis, herein, we are interested in describing a new synthetic strategy for the synthesis of tetrahydro-indolones via a Rh­(III)-catalyzed [3 + 2] annulation reaction from simple and readily available enaminones with iodonium ylides (Scheme h).…”