Hydrosilylation of Carbonyl Compounds Catalyzed through a Lithiated Hydrazone Derivative

Abstract

A well-defined lithiated hydrazone derivative has been synthesized and fully characterized through various analytical platforms, including multinuclear (1H, 13C, 15N, 7Li) and two-dimensional NMR, high-resolution MS spectrometry, IR, and X-ray diffraction crystallography. It behaves as a binuclear species in the solid state and as a monomeric contact ion pair in solution. It has also been tested as a catalyst in hydrosilylation reactions, being the first lithium hydrazone reported to catalyze the full conversion of carbonyls of different nature into alcohols in short reaction times, at room temperature, and with catalyst loadings equal to or below 0.5 mol %. Kinetic studies have proven fractional order dependences with respect to ketone and silane and first order dependence in the case of the catalyst. The proposed reaction mechanism is characterized by the nucleophilic addition of the lithium hydrazonide to the silicon atom of the silane to give a five-coordinate silicon species.

Molecular Main Group Metal Hydrides

“…Mechanistic studies of the reaction of PhSiH 3 and K­[O t Bu] in THF- d 8 at −70 °C allowed the identification of the hydridosilicate, K­[Ph­( t BuO)­SiH 3 ], which dismutated to a mixture of K­[Ph­( t BuO)­SiH 3 ], K­[Ph­( t BuO) 2 SiH 2 ], K­[Ph 2 ( t BuO) 2 SiH], K­[PhSiH 4 ], and K­[SiH 5 ] upon warming to −40 °C, and which were proposed as the actual reducing species. In closely related work, K­[O t Bu] has also been reported as a catalyst for the reduction of enamines with alkoxysilanes, while K 2 CO 3 , Cs 2 CO 3 , KOH, and a lithiated 1-hydrazino­anthraquinone derivative have been described for a related range of transformations, under which conditions similar silicate formation also most likely prevails. − As a very recent follow up to this latter work, Ortuño and Fernández have also reported a computational and experimental study, which highlights the accelerating role of de-aggregation agents, especially HMPA, during the Li-catalyzed hydrosilylation of acetophenone in THF solution …”

Lithium anthraquinoids as catalysts in the ROP of lactide and caprolactone into cyclic polymers

“…In pursuit of a more extensive exploration of the anthraquinone possibilities in the ROP of cyclic esters, three new mono-substituted anthraquinoid ligands with different pendant functionalities were synthesized (Scheme 3). 27 Ligands 1b–1d were obtained from inexpensive starting materials in high yields using 1-hydrazinoanthraquinone, which was prepared by following the reported methods. 28 The details regarding their synthetic procedures and full characterization can be found in the Experimental section and the ESI †…”

Donor Functionalized Iron(II) N‐Heterocyclic Carbene Complexes in Transfer Hydrogenation Reactions

“…The shape of the gradient pulse was smoothed rectangular shape (SMSQ), and its strength varied automatically in the course of the experiments. The D values were determined from the slope of the regression line ln(I/I 0 ) vs. G 2 , as already described [ 24 ] . All diffusion processing and molecular size estimations were performed by using the DiffAtOnce software package.…”