Et2Zn-mediated stoichiometric C(sp)-H silylation of 1-alkynes and chlorosilanes

Asymmetric Hydrosilylation of β-Silyl Styrenes Catalyzed by a Chiral Palladium Complex

A palladium complex coordinated with a chiral SIPHOS ligand was evaluated as an efficient catalyst for asymmetric hydrosilylation of β-silyl styrenes with trichlorosilane and 23 1,2-bis(silyl) chiral compounds were produced. Good to excellent enantioselectivities were observed with 1-aryl-2-silyl ethanols, where the trichlorosilyl groups of the hydrosilylation products were selectively converted into a hydroxyl group in the presence of pre-installed trialkylsilyl groups. Asymmetric hydrosilylation of β-silyl styrenes followed by methylation of the trichlorosilyl group gave stable 1,2-bis(silyl) chiral compounds 4 with excellent yields. DFT calculations of hydridopalladium B coordinated with a SIPHOS ligand, an intermediate of the hydrosilylation reaction, established the optical structures to be energy minima, and the structural information could well illustrate the enantioselectivity for the hydrosilylation reaction.

Fluoride Ion-Initiated Decarboxylation of Silyl Alkynoates to Alkynylsilanes

This communication describes the development of a metal-free catalytic decarboxylation of silyl alkynoates to alkynylsilanes. Treatment of a silyl alkynoate with a catalytic amount of tetrabutylammonium difluorotriphenylsilicate (TBAT) in N,N-dimethylformamide at 150 °C resulted in decarboxylation to give the corresponding alkynylsilane in good to excellent yield (75 → 95%). The TBAT system was applicable to the decarboxylation of sterically demanding silyl alkynoates such as tert-butyldiphenylsilyl 3-phenylpropiolate. Mechanistic studies revealed that the tetrabutylammonium alkynoate derived from TBAT and the silyl alkynoate act as a catalyst for the decarboxylation.

Mechanistic investigation of zinc-promoted silylation of phenylacetylene and chlorosilane: a combined experimental and computational study

The zinc-promoted silylation method is of great importance to synthesize high-performance silicon-containing arylacetylene (PSA) resins in the industry. However, it is difficult to eliminate the accompanied by-product of terminal alkenes due to the lack of mechanistic understanding of the silylation. The initiation of zinc-promoted silylation is facilitated by the interaction between zinc and phenylacetylene. Our DFT calculations indicated that the intermolecular hydrogen transfer of phenylacetylene follows an ionic pathway, which generates a phenylacetylene anion and the corresponding alkene moieties on the zinc surface. The styrene by-product is observed in this stage, with its alkene moieties desorbing as radicals into the solvent under the high reaction temperature. Three possible intermediates of surface phenylacetylene anions were proposed including PhC[triple bond, length as m-dash]C-Zn, PhC[triple bond, length as m-dash]CZnCl, and (PhC[triple bond, length as m-dash]C)2Zn. These carbanion-zinc intermediates undergo an SN2 reaction with Me3SiCl to afford the alkynylsilane on the zinc surface, which is calculated to be the rate-determining step for the zinc-promoted silylation reaction.