Gladyshev et al.

, (1976)

An efficient solvent-free route to silyl esters and silyl ethers

Ojima, Yuko,Yamaguchi, Kazuya,Mizuno, Noritaka

scheme or table, p. 1405 - 1411 (2009/12/07)

Dinuclear metal complexes, especially (p-cymene)ruthenium dichloride dimer {[RuCl2(p-cymene)]2}, have been found to exhibit high catalytic performance for the dehydrosilylation of various kinds of carboxylic acids and alcohols. The dehydrosilylation with [RuCl2(p-cymene)] 2 proceeded efficiently with only one equivalent of silane with respect to substrate (carboxylic acids or alcohols) under solvent-free conditions to give the corresponding silyl esters and ethers in excellent yields with a high turnover number (TON) and frequency (TOF). The 1H NMR spectrum of a toluene-d8 solution of [RuCl2(p-cymene)] 2 and a silane showed a signal assignable to the ruthenium hydride species. In contrast, no new signals were detected in the 1H NMR spectrum of a toluene-d8 solution of [RuCl2(p-cymene)] 2 and a carboxylic acid or an alcohol. There-fore, the ruthenium metal in [RuCl2(p-cymene)]2 activates a silane to afford the hydride intermediate, possibly a silylmetal hydride species. Then, the nucleophilic attack of a substrate (carboxylic acid or alcohol) to the hydride intermediate proceeds to give the corresponding silylated product. The present dehydrosilylation with an optically active silane proceeded exclusively under inversion of stereochemistry at the chiral silicon center, suggesting that the nucleophilic attack of a substrate to the hydride intermediate occurs from the backside of the ruthenium-silicon bond.

Esters of (Hydroxymethyl)diorganylsilanes: Synthesis and Thermally Induced Rearrangement

Tacke, Reinhold,Wiesenberger, Frank,Becker, Beate,Rohr-Aehle, Regine,Schneider, Petra B.,et al.

, p. 591 - 606 (2007/10/02)

Twenty silanes of the type R1R2Si(H)CH3OR3 (A) were synthesized 1,R2 = Me, Ph, 1-naphthyl, PhCH2, Me3SiCH2; OR3 = OC(O)Me, OC(O)CF3, OS(O)CF3, OP(O)Ph2, OC(O)Cl> and studied for their thermal behaviour.The silanes A undergo a thermally induced rearrangement to give the corresponding silanes R1R2Si(OR3)Me (B).For compounds with OR3 = OC(O)Cl, an additional decarboxylation takes place to yield the chlorosilanes R1R2Si(Cl)Me.Except for the derivatives with OR3 = OC(O)Cl, the energetic (reaction enthalpy) and kinetic data (reaction order, frequency factor, enthalpy and entropy of activation) of these reactions were studied by means of differential scanning calorimetry (DSC).In addition the kinetics of all reactions were investigated by 1H-NMR spectroscopy.The transition state of the rearrangement was investigated by an ab initio study based on the model compound H3SiCH2OC(O)H MeH2SiOC(O)H>.The theoretical data and the experimentally obtained energetic and kinetic data are discussed in terms of mechanistic aspects of the rearrangement reaction A -> B.