Homogeneous hydrogenation of electron‐deficient alkenes by iridium complexes |
| |
Authors: | Volodymyr Semeniuchenko Thomas E. Exner Volodymyr Khilya Ulrich Groth |
| |
Affiliation: | 1. Fachbereich Chemie und Konstanz Research School Chemical Biology der Universit?t Konstanz, Fach M‐720, Universit?tsstrasse 10, D‐78457 Konstanz, Germany;2. Department of Chemistry, National Taras Shevchenko University, Volodymyrska str. 62, Kyiv‐33, 01033, Ukraine |
| |
Abstract: | The catalytic homogeneous hydrogenation of electron‐deficient alkenes (nucleophilic hydrogenation) was achieved in the presence of iridium complexes and a base as co‐catalyst. Contrary to hydrogenation of electron‐rich alkenes, which is inactivated by bases, the hydrogenation of the electron‐deficient alkenes turned out to be base activated. Here, we present a more thorough study on the capacities but also limitations of this new reaction mechanism using screenings of the reaction conditions as well as different Ir complexes and substrates. The formation of a catalytically active Ir complex is proposed. The active complex usually attacks a soft electron‐deficient atom, if more than one possibility exists (as shown by density functional theory computations). Additionally, first examples of enantiomeric enrichments in the presence of chiral Ir complexes are presented. The high catalyst load needed and the moderate yields show that the active complex is very unstable under conditions of nucleophilic hydrogenation and is quickly deactivated, which has to be addressed in further studies. Copyright © 2011 John Wiley & Sons, Ltd. |
| |
Keywords: | hydrogenation iridium homogeneous catalysis alkenes density functional calculations |
|
|