Larisa Borisova

A NOVEL ROUTE TO PENTACOORDINATED ORGANYLSILANES AND -GERMANES

Abstract New convenient methods of sila- and germatranes synthesis from ethoxy- and tetraorganylsilanes and -germanes have been elaborated. The reaction of ethoxysilanes with boratrane in the presence of catalytic amounts of metal alcoholates has been investigated. Dimethylformamide (DMF) as a solvent and NaOEt as a catalyst used instead of xylene and Al(O i− Pr) 3 were found to give better yields. The possibility of using alkoxy-, aminosilanes, tetraethoxygermane and even tetraorganylsilanes in this reaction leading to the corresponding atranes with good yields has been demonstrated. Triethanolamine in the presence of catalytic amounts of base or CsF easily substitutes furyl-, dihydrofuryl-, dihydropyranyl- and thienyl groups in tris- and tetraheterylsilanes, leading to organylsilatranes with good to excellent yields.

Cleavage of SiC and GeC bonds in heterylsilanes and -germanes by organolithium reagents

Abstract Organolithium reagents RLi can cleave SiC and GeC bonds in heteryisilanes and -germanes substituting furyl, dihydrofuryl and dihydropyranyl groups for the organolithium residue R.

Synthesis of new vinylsilanes containing an asymmetric silicon via platinum catalyzed hydrosilylation of acetylene and monosubstituted alkynes

Abstract A series of new racemic vinylsilanes has been obtained by hydrosilylation reaction of acetylene and monosubstituted alkynes with (±)-α-NpPhMeSiH and (±)-N(CH 2 CH 2 O) 3 SiCH 2 PhMeSiH in the presence of platinum-containing catalysts.

Reaction of heteryl-silanes and -germanes with metal hydrides

Abstract A series of heteryl-silanes and -germanes 1 containing a different number of dihydrofuryl and dihydropyranyl groups at the metal atom has been obtained by means of the lithium synthesis. Subsequent substitution of heteryl group for hydride ion occurs during the reaction of the compounds formed with LiAlH4. The hydrides and boron hydrides of lithium and sodium are able to eliminate the dihydrofuryl group from the most reactive bis[2-(4,5-dihydrofuryl)]methyl-silane (7). The reaction of tris-heteryl-silanes and -germanes with LiAlH4 gives [2-(4,5-dihydrofuryl)]methylsilane (12), [2-(5,6-dihydro-4H-pyranyl)]methylsilane (14) and [2-(4,5-dihydrofuryl)]methylgermane (13) in good yields, which are otherwise difficult to obtain.

Cleavage of SiC and GeC bonds with lithium aluminium hydride

Abstract Lithium aluminium hydride can cleave SiC and GeC bonds, providing a useful means for substituting furyl, dihydrofuryl and tetrahydrofuryl groups. Spectra are described of compounds prepared by this means.

Organylsilatranes from the reaction of tetraorganylsilanes with triethanolamine

Abstract Triethanolamine selectively cleaves SiC bonds in heterylsilanes (3) under basic/nucleophilic catalysis, leading to organylsilatranes (4) with good to excellent yields.

Palladium-catalyzed rearrangement of silanes containing oxygen or halogen α to silicon

Abstract Rearrangements of tetrahydrofuryl- and tetrahydropyranyl-hydrosilanes to oxasilaalkanes, of acetoxymethyl-hydrosilanes to acetoxysilanes, and halogenomethyl-hydrosilanes to halogenosilanes in the presence of palladium catalyst have been studied. The reaction has been shown to proceed more rapidly in tetrahydrofuran and hexane than in benzene or acetonitrile. The progressive replacement of the methyl groups on the silicon atom by phenyl groups slowed down the rearrangement, as did change from five-membered to six-membered heterocycles.

Synthesis and structure of silylmethylsilatranes RR′R″SiCH2Si(OCH2CH23N

Abstract New alkoxysilylmethylsilatranes MePhROSiCH2 Si(OCH 2 CH 2 3 N have been obtained from the reaction of silylmethylsilatrane MePhHSiCH2 Si(OCH 2 CH 2 ) 3 N with alcohols in the presence of H2PtCl6·6H2O. Methylphenylsilylmethylsilatrane (1) reacted with H2O in the presence of Pd to give methylphenyl(silatranylmethylsilanol (6 which was converted to siloxane (7) and germoxane (8). The molecular structures of the silatrane 1 and silanol 6 have been determined by an X-ray diffraction study which revealed the presence of intramolecular OH … O bond in the latter.

Silatranes from reactions of chloromethylsilatrane with chlorosilanes and magnesium in tetrahydrofuran

Abstract Some silatranylmethylsilanes have been obtained by reaction of chloromethylsilatrane with chloro- silanes and magnesium in THF (i.e. under Barbier conditions).

Reactions of dihydrofurylsilanes with O- and N-nucleophiles

It was shown that the reaction of 4,5-dihydro-2-furylsilanes with alcohols and lithium N,N-diethylamide leads to substitution of the dihydrofuryl group by the nucleophilic residue.