Ru‐Catalyzed Carbonylative Murai Reaction: Directed C3‐Acylation of Biomass‐Derived 2‐Formyl Heteroaromatics

Abstract

The Murai reaction is a ruthenium‐catalyzed transformation leading to alkylated arenes through the C−C bond formation between an alkene and an arene bearing a directing group. Discovered in the nineties, this useful C−H activation based coupling has been the object of intense study since its discovery. After having studied the Murai reaction on 2‐formylfurans of biomass derivation, we describe here the carbonylative version applied to 2‐formylfurans, 2‐formylpyrrols and 2‐formylthiophenes. This acylation reaction takes place regioselectively at C3 position of the heterocyclopentadienes thanks to the installation of removable imine directing groups. The transformation can be achieved by treating the two reaction partners with a catalytic amount of Ru3(CO)12, in toluene at 120–150 °C, after CO bubbling, at atmospheric pressure. DFT computations of the full catalytic cycle help in deciphering the mechanism of this transformation, and to rationalize the different behaviors depending on the nature of imine directing groups.

Catalytic C−H Functionalization of Unreactive Furan Cores in Bio‐Derived Platform Chemicals

“…The carbonylative version of the Murai reaction was recently reported by the same authors [36] . Short‐time bubbling of carbon monoxide through the reaction mixture allows to obtain a number of C3‐acylated FPC (Scheme 2).…”

“… Ru‐catalyzed carbonylative Murai reaction of protected PNP‐imine derivatives of HMF with vinylsilanes and carbon monoxide [36] …”

“…The carbonylative version of the Murai reaction was recently reported by the same authors. [36] Short-time bubbling of carbon monoxide through the reaction mixture allows to obtain a number of C3-acylated FPC (Scheme 2). Stable p-methoxyphenyl-imine (PMP-imine) fragment was used as a directing group in this case, which allows isolation of products 5-10 Scheme 1.…”

“…Ru-catalyzed carbonylative Murai reaction of protected PNP-imine derivatives of HMF with vinylsilanes and carbon monoxide. [36] without hydrolysis of imine fragment on silica. The aldehyde fragment still can be easily obtained by hydrolysis of imines with 1 m hydrochloric acid in diethyl ether in excellent yields.…”

Ru(0)-Catalyzed Alkenylation of 2-Carboxaldimine Heterocyclopenta-dienes with H2 Transfer

“…[32][33][34] As part of a long term project directed toward the sustainable C-H functionalization of aldimine-armed heterocyclopentadienes of biomass derivation such as furan, [35][36][37] pyrrole, 38,39 as well as thiophene units, we have recently developed several directed Ru(0)-catalyzed C3-functionalizations (Scheme 1A), such as: the alkylation (Murai reaction 40 ) of N,N'-bidentate furfurylimines with vinylsilane or styrene derivatives (a), 41 the arylation of electron-rich furfurylimines with arylboronates (b), 42,43 and the acylation (carbonylative Murai reaction) of furan-(c) or pyrrole-based p-methoxyphenyl imines or N,N'-bidentate imines (d) under CO atmosphere with vinylsilane or styrene partners. 44 However, the directed C3-H alkenylation of 2-formyl-heterocyclopentadiene units, which overwhelms the natural C5 electrophilic preference of these heterocycles, 45 remains a challenge.…”