Manganese-catalysed transfer hydrogenation of esters.

Conor L Oates,Magnus B Widegren,Matthew L Clarke

doi:10.1039/d0cc02598d

Abstract

Manganese catalysed ester reduction using ethanol as a hydrogen transfer agent in place of dihydrogen is reported. High yields can be achieved for a range of substrates using 1 mol% of a Mn(i) catalyst, with an alkoxide promoter. The catalyst is derived from a tridentate P,N,N ligand.

Highlights

Manganese catalysed ester reduction using ethanol as a hydrogen transfer agent in place of dihydrogen is reported
High yields can be achieved for a range of substrates using 1 mol% of a Mn(I) catalyst, with an alkoxide promoter
Given the level of interest in transfer hydrogenation, relatively few papers have described transfer hydrogenation of esters (Fig. 1).5a–d Dubey and Khaskin reported the use of just 1 mol% of a ruthenium catalyst, using ethanol as reductant and an alkoxide co-catalyst.5b The discovery by de Vries and co-workers of an effective base-free Fe borohydride catalyst using ethanol as reductant, this time requiring 5 mol% catalyst loading, is a significant milestone.5d Catalysts such as this, which are derived from an indefinitely sustainable metal source, and that permit higher catalyst impurities than the 5–10 ppm generally required as a minimum for precious metal based catalysts[6] are highly desirable

Summary

Introduction

Manganese catalysed ester reduction using ethanol as a hydrogen transfer agent in place of dihydrogen is reported. Our objective was to enable a Mn-based catalyst to conduct ester transfer hydrogenation at a catalyst loading below the 5 mol% level used by de Vries and co-workers.5d A selection of our Mn catalysts were investigated using conditions relatively similar to those used in ref.

Objectives

Results

Conclusion