Site-selective C–H bond carbonylation with CO2 and cobalt-catalysis

Abstract

Utilization of anthropogenic greenhouse gas CO₂ for catalytic C–C bond formation via conversion to essentially valuable C1 synthons like CO is very challenging. The requirement of an efficient catalyst that has the ability to convert CO₂ into CO and activate inert C–H bonds is the bottleneck. We herein demonstrate a tandem approach accomplished in a two-chamber system for efficient fluoride-mediated generation of CO from CO₂ using disilane as a deoxygenating reagent and utilization of the in situ-produced CO gas for C–H bond carbonylation using earth-abundant cobalt catalysts. The ease of handling CO₂ gas at atmospheric pressure allows us to prepare ¹³C labelled compounds which are otherwise difficult to achieve. The procedure developed makes it possible to utilize CO₂ as a CO source, which can be widely applied as a C1 synthon that can be incorporated between C–H and N–H bonds of aromatic, hetero-aromatic and aliphatic carboxamides for the synthesis of various cyclic imides including spirocycles in a site-selective fashion. The late-stage derivatization of a well-known angiotensin receptor blocker (ARB), Telmisartan, and a well-known drug for very low-density lipoproteins (VLDLs), Gemfibrozil, is demonstrated. Further, to showcase the generality of the reaction, various pharmacologically important and privileged scaffolds like xanthone, coumarin and isatin have been synthesized with CO₂ under atmospheric pressure.