Harnessing Rhodium-Catalyzed C–H Activation: Regioselective Cascade Annulation for Fused Polyheterocycles

Abstract

In the realm of transition-metal catalyzed arene functionalization, rhodium(III) catalysis is considered as exemplary due to its propensity to activate C−H bonds to obtain comprehensive molecular assembly. Herein, we demonstrate a new rhodium(III) catalyzed assembly of polyheterocyclic scaffolds via C−H activation and regioselective annulation of 4-arylbut-3-yn-1-amines with 4-hydroxy-2-alkynoates. Heterocyclization and transmetalation prior to annulation is the key for initiation of this relay redox-neutral catalytic cascade.

Recent Advances in the Synthesis of 5‐MemberedN‐Heterocycles via Rhodium Catalysed Cascade Reactions

“…Then, coordination of 4-hydroxy-2-alkynoate with B followed by sequential regioselective insertion, reductive elimination and lactonization provided the final product 205 (Scheme 58). [122] Indazole derivatives are one of the prominent heterocyclic scaffolds widely found in nature possessing potential biological activity. [123a,b] Over the past decade transition metal catalyzed CÀ H activation was found to be a robust and efficient synthetic tool for the construction of CÀ N and CÀ C bond.…”

“…Regioselective cascade annulation for fused polyheterocycles via rhodium-catalyzed CÀ H activation. [122] ylides emerged as a novel carbene substituent in Rhodium catalyzed CÀ H functionalization serving both as C1 and C2 synthons to access heterocyclic products. [125d-g] Previously, Cheng group developed a novel route for the synthesis of indoloindolones via rhodium-catalyzed [4 + 1] annulation reaction between sulfoxonium ylides and anthranils.…”

“…Then, coordination of 4‐hydroxy‐2‐alkynoate with B followed by sequential regioselective insertion, reductive elimination and lactonization provided the final product 205 (Scheme 58). [122] …”

“… Regioselective cascade annulation for fused polyheterocycles via rhodium‐catalyzed C−H activation [122] …”

Rhodium-Catalyzed Coordination-Assisted Regioselective and Migratory Three-Point Double Annulation of o-Alkenyl Phenols with Tertiary Propargyl Alcohols

“…Inert C–H activation has been gradually recognized as a reliable dimension of organic synthesis after the discovery of various catalytic systems to functionalize many C–H bonds that were previously regarded as being passive for the reactions. Among various metals, ,,, rhodium-catalyzed C–H functionalizations ,,,− , display unique reactivity patterns for the orchestration of multifaceted carbo/heterocycles in an operationally simple and synthetically convenient manner. Distinguished by its exceptional functional group tolerance and cryptic reactivity, rhodium catalysis could profusely expand the choice of feedstocks.…”