Phosphine‐Catalyzed Activation of Phenylsilane for Benzaldehyde Reduction

Abstract

Hydrosilylation reactions are commonly used for the reduction of carbonyl bonds in fine chemistry, catalyzed by transition metal complexes. The current challenge is to expand the scope of metal-free alternative catalysts, including in particular organocatalysts. This work describes the organocatalyzed hydrosilylation of benzaldehyde with a phosphine, introduced at 10 mol%, and phenylsilane at room temperature. The activation of phenylsilane was highly dependent on the physical properties of the solvent such as the polarity, and the highest conversions were obtained in acetonitrile and propylene carbonate with yields of 46 % and 97 %, respectively. The best results of the screening over 13 phosphines and phosphites were obtained with linear trialkylphoshines (PMe 3 , P n Bu 3 , POct 3 ), indicating the importance of their nucleophilicity, with yields of 88 %, 46 % and 56 %, respectively. With the help of heteronuclear 1 HÀ 29 Si NMR spectroscopy, the products of the hydrosilylation (PhSiH 3-n (OBn) n ) were identified, allowing a monitoring of the concentration in the different species, and thereby of their reactivity. The reaction displayed an induction period of ca. 60 min, followed by the sequential hydrosilylations presenting various reaction rates. In agreement with the formation of partial charges in the intermediate state, we propose a mechanism based on a hypervalent silicon center via the Lewis base activation of the silicon Lewis acid.

Phosphines on Colloidal Nickel Nanocatalysts to Lower the Onset Temperature of Terminal Alkynes Hydrogenation

“…In order to rationalize this first set of results, the phosphines were positioned on a stereoelectronic map, as presented in a previous work . This is a two-dimensional space based on the phosphine Tolman electronic parameter (TEP) and on a steric hindrance parameter, for which we selected the free ligand descriptor He 8 _steric developed for phosphorus donor ligands. , The map was color-coded, with lighter colors representing higher conversion (Figure ).…”

Phosphine‐Enhanced Semi‐Hydrogenation of Phenylacetylene by Cobalt Phosphide Nano‐Urchins

“…Following a methodology presented in an earlier work, [42] the influence of the phosphine's substituents was rationalized via a stereo‐electronic map (Figure 2) representing the phenylacetylene conversion on a two‐dimensional space based on the phosphine Tolman Electronic Parameter (TEP) [32] and a steric hindrance parameter. The reliability of the Tolman cone angle, determined from nickel‐phosphine complexes and generally used as a steric hindrance parameter, has been recently questioned when considering interactions with nanoparticle surfaces.…”