Synthesis and catalytic application of novel binaphthyl-derived phosphorous ligands
Kathrin Junge, Bernhard Hagemann, Stephan Enthaler, Giulia Erre, and Matthias Beller*
Leibniz-Institut für Katalyse e.V. an der Universität Rostock, Albert-Einstein-Straße 29a, D- 18059 Rostock, Germany
E-mail: matthias.beller@catalysis.de
Dedicated to Prof. Dr. Lutz F. Tietze on the occasion of his 65th birthday
Abstract
We describe our recent achievements in the synthesis of chiral phosphorous ligands and their application in catalytic asymmetric hydrogenation reactions. Special attention is given to the development of novel binaphthophosphepine ligands. Starting from enantiomerically pure 1,1’- binaphthol or 2,2’-dimethyl-1,1’-binaphthyl and the building blocks A or B, new chelating P- ligands have been synthesized in one step in good to excellent yields (68–95%). The resulting chiral bidentate phosphines, phosphites and phosphonites were tested in various asymmetric hydrogenation benchmark reactions. Interestingly, small structural changes within the ligands exhibit a significant influence on the enantioselectivity of the hydrogenation reactions.
Keywords: Asymmetric hydrogenation, homogeneous catalysis, chiral phosphines
Introduction
Catalysis, which is the science of accelerating chemical transformations, enables the chemical and pharmaceutical industry to offer a wide range of products for our health, environment, and nutrition. This makes catalysts indispensable for the needs of today’s society and important tools for increasing sustainability. Catalysts are mainly used for environmental protection, the production of bulk and fine chemicals, oil processing in refineries, and polymer synthesis.
For some years our main area of scientific interest has been applied homogeneous catalysis with organometallic complexes. A key issue for controlling the activity, productivity, and selectivity of a given transition metal complex is the synthesis of molecularly defined catalytic centers. In other words, the electronic and steric properties of each active center can be controlled by using organic ligands, which coordinate to the metal center. Thus, “ligand- tailoring” constitutes an extremely powerful tool to control all kinds of selectivity for a desired catalytic reaction and to influence catalyst stability and activity. Due to the advancements in organometallic chemistry and organic ligand synthesis, nowadays a plethora of ligands [P-, N-,
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