Catalytic transformation of functionalized carboxylic acids using multifunctional rhenium complexes

Masayuki Naruto,Susumu Saito,Katsuaki Toda,Santosh Agrawal

doi:10.1038/s41598-017-03436-y

Masayuki Naruto, Susumu Saito + Show 2 more

Open Access

https://doi.org/10.1038/s41598-017-03436-y

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Journal: Scientific Reports	Publication Date: Jun 13, 2017
Citations: 30	License type: open-access

Affiliation: Nagoya University

Abstract

Carboxylic acids (CAs) are one of the most ubiquitous and important chemical feedstocks available from biorenewable resources, CO2, and the petrochemical industry. Unfortunately, chemoselective catalytic transformations of CHnCO2H (n = 1–3) groups into other functionalities remain a significant challenge. Herein, we report rheniumV complexes as extremely effective precatalysts for this purpose. Compared to previously reported heterogeneous and homogeneous catalysts derived from high- or low-valent metals, the present method involves a α-C–H bond functionalization, a hydrogenation, and a hydrogenolysis, which affords functionalized alcohols with a wide substrate scope and high chemoselectivity under relatively mild reaction conditions. The results represent an important step toward a paradigm shift from ‘low-valent’ to ‘high-valent’ metal complexes by exploring a new portfolio of selective functional group transformations of highly oxygenated organic substrates, as well as toward the exploitation of CAs as a valuable biorenewable feedstock.

Highlights

Carboxylic acids (CAs) are abundantly available from a variety of natural resources and the petrochemical industry, while several emerging technologies aim to produce CAs via thermal[1,2,3,4] or photo-induced[5,6,7] immobilization of CO2 in organic frameworks
CO2H moieties have been used as directing groups for the Pd-catalyzed C–H bond functionalization of spatially distal sp[2] or sp[3] carbon atoms[16, 17], and as traceless activating groups for decarboxylative carbon–carbon bond formations[24,25,26,27]
Despite the numerous beneficial features of low-valent metal species, the catalytic functional group transformation (FGT) of CAs frequently suffers from several drawbacks, i.e., side reactions including the oxidative addition of the substrate at high temperatures, decarboxylation, and over-reduction (Fig. 1a)[23], as well as catalyst deactivation by ligation/

Summary

Introduction

Carboxylic acids (CAs) are abundantly available from a variety of natural resources and the petrochemical industry, while several emerging technologies aim to produce CAs via thermal[1,2,3,4] or photo-induced[5,6,7] immobilization of CO2 in organic frameworks. The functional group transformation (FGT) and subsequent reduction of CAs represent an important research subject to furnish alcohols for platform/fine chemicals[1,2,3,4,5,6,7,8,9,10,11], biofuels[11,12,13], and electric power-storage materials[14] Among those FGTs, the catalytic C–H bond functionalization of CAs15–17, followed by hydrogenation[18,19,20,21,22,23], could potentially widen the diversity of alcohols available. The majority of high-valent Re complexes have far been used for oxidation[31] and deoxydehydration[31, 32], rather than for FGT of CA (α-C–H functionalization[15] and hydrogenation[23, 33])

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Conclusion