Synlett 2014; 25(10): 1371-1380
DOI: 10.1055/s-0033-1340849
account
© Georg Thieme Verlag Stuttgart · New York

Catalytic Hydrogenation of Low-Reactivity Carbonyl Groups Using Bifunc­tional Chiral Tridentate Ligands

Matthew L. Clarke*
School of Chemistry, University of St Andrews, EaStCHEM, St Andrews, Fife, KY16 9ST, UK   Fax: +44(133)4463808   Email: mc28@st-andrews.ac.uk
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Further Information

Publication History

Received: 28 October 2013

Accepted after revision: 14 January 2014

Publication Date:
11 March 2014 (online)


Abstract

This account describes studies on the catalytic hydrogenation of carbonyl groups that are not readily reduced. The development of well-defined chiral phosphine–diamine ruthenium catalysts for hydrogenation of ketones and esters is described. These chiral catalysts promote the hydrogenation of ketones functionalised with tertiary alkyl and gem-dimethyl groups with enantioselectivities of up to 98% ee. They also reduce a range of heterocyclic and nitrile-functionalised ketones that react slowly with or inhibit other catalysts. Changing from ruthenium to iridium complexes gives highly selective catalysts that also hydrogenate (the more reactive) secondary alkyl functionalised ketones, including those with unprotected amines. These catalysts operate rapidly at room temperature, require low catalysts loadings, and deliver up to 98% ee. Achiral variants of these catalysts also promote the hydrogenation of esters under mild conditions. This account also describes our studies that shed light on the mechanism of action of these catalysts, and a stereochemical model is proposed.

1 Introduction

2 Hydrogenation of Low-Reactivity Carbonyl Functions

3 Mechanism

4 Applications of the Catalysts

5 Outlook