A triphos-modified tungsten piano-stool complex for the homogeneous (conjugate) hydrogenation of ketones and esters
Thomas Vielhaber, Kirill Faust, Thomas Bögl, Wolfgang Schöfberger, Christoph Topf
Abstract
We disclose the synthesis, characterization, and catalytic application of a triphos-tagged, non-pincer-type tungsten complex. The pertinent W-based half-sandwich compound was used in the homogeneous hydrogenation of ketones and esters to afford the corresponding alcohols. Furthermore, the introduced base metal catalyst facilitated the conjugate reduction of enoates to yield the respective CC-bond-free esters. Most of the applied substrate ketones were convertible under very mild reaction conditions (room temperature, 5 bar H2) in the presence of t–BuONa. The exchange of the cation in the auxiliary base from Na+ to Li+ turned out to be crucial for the successful reduction of the carbonyl ester group. The deployed organometallic complex is readily weighable and can be handled on the laboratory bench outside a sealed glove box system.