2295-12-7Relevant academic research and scientific papers
Silaheterocyclen II. Erzeugung und Cycloadditionsreaktionen der Neopentylsilaethene (R = H, Me)
Auner, N.
, p. 83 - 104 (1987)
The monosilacyclobutanes (3) and (4) react with LiBut in pentane to yield the neopentylsilaethenes (1) and (2), respectively.Without suitable reactants, 1 and 2 undergo cyclodimerization to 2,4-dineopentyl-1,3-disilacyclobutanes; in the presence of organic dienes they form cycloaddition compounds: with cyclopentadiene only products are obtained, with cyclohexa-1,3-diene - and -cycloaddition reactions occur at comparable rates; in the reaction with norbornadiene the - is favoured over the -cycloaddition, whereas with 2,3-dimethyl-1,3-butadiene the -process together with the ene-reaction predominate.The -cycloadducts indicate a multistep-pathway, probably with participation of lithiated species, whereas the - and -cycloaddition reactions confirm that the silaethenes 1 and 2 are formed as reactive intermediates.
Electrochemical synthesis of cyclic alkylsilanes
Jouikov, V.,Krasnov, V.
, p. 213 - 220 (1995)
The electrochemical reduction of aliphatic α,ω-dibromides in the presence of polychlorosilanes of the formula RnSiCl(4-n) (n=0, 2) was shown to afford heterocyclic silicon compounds in good yield (up to 91percent).In contrast to non-electrochemical methods of synthesis of silacycloalkanes, based on the ring closure of terminal unsaturated compounds, the electrochemical route does not produce α-methylated byproducts and the heterocycle formation occurs quite selectively.The yield of cyclic organosilicon compounds goes through a maximum for 1,1-dimethyl-1-silacyclopentane (91percent) and roughly decreases for 1,1-dimethyl-1-silacyclobutane (18percent) and 1,1-dimethyl-1-sialacycloheptane (57percent).The formation of 5-silaspiro nonane by the electrochemical process occurs with high selectivity despite the multitude of possible reaction pathways and the high probability of polymer formation due to the high functionality of the silicon.The relatively high selectivity of the electrochemical ring closure is suggested to be due to the orientating effect of an electrode in the course of an irreversible reduction of a C-Hal bond in the monosilylated intermediate.A possible mechanism for the process is discussed.Keywords: Silicon; Electrochemistry; Electrochemical synthesis
SYNTHETIC PROCESS FOR CYCLIC ORGANOSILANES
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Page/Page column 7, (2008/06/13)
A process for preparing a cyclic organosilane using a solvent that promotes ring-closure reactions between an organosilane compound and a dihalo organic compound is disclosed. The ring-closure reactions may form a 4-, 5- or 6-member cyclic organosilane. The process involves a mixture including a dihalo organic compound, an organosilane having at least two functional groups, a solvent and magnesium (Mg). The two functional groups in the organosilane may include halogen, alkoxy or a combination thereof. In the presence of Mg, a Grignard intermediate is formed from the dihalo organic compound in the mixture. The solvent favors intra-molecular or self-coupling reactions of the Grignard intermediate. The intra-molecular or self-coupling reaction promotes ring-closure reaction of the Grignard intermediate to form the cyclic organosilane.
Gas phase studies of silacyclobutanes: Recent developments employing triple quadrupole detection
Damrauer, Robert,Hankin, Joseph A.
, p. 93 - 98 (2007/10/03)
Four silacyclobutyl anions have been prepared and studied by gas phase ion-molecule chemistry using newly modified tandem flowing afterglow instrumentation. These silacyclobutyl anions, which include a pentacoordinate adduct of 1,1-dimethylsilacyclobutane and fluoride and an α-silylcarbanion, siloxide, and mercaptide corresponding to 1,1-dimethylsilacyclobutane, have been characterized by their chemical reactivity and collision-induced loss of ethylene under a variety of conditions. The C-H, O-H, and S-H gas phase acidities of 1,1-dimethylsilacyclobutane, 1-hydroxy-1-methylsilacyclobutane, and 1-mercapto-1-methylsilacyclobutane have been measured and show no effect of the silacyclobutyl attachment. The full capabilities of the newly modified instrumentation include the mass selection of ions, their chemical characterization, collision-induced dissociation of both mass selected ions and those prepared by chemical reactions, and triple quadrupole detection.
SILYL AND SILYLMETHYL RADICALS, SILYLENES, SILA-ALKENES, AND SMALL RING SILACYCLES IN REACTIONS OF ORGANOCHLOROSILANES WITH ALKALI METAL VAPOURS
Gusel'nikov, L. E.,Polyakov, Yu. P.,Volnina, E. A.,Nametkin, N. S.
, p. 189 - 204 (2007/10/02)
Dehalogenation of the organochlorosilanes Me3SiCl (I), Me2PrSiCl (II), Me3SiSiMe2Cl (III), Me3SiCH2SiMe2Cl (IV), ClCH2SiMe3 (V), ClCH2SiMe2SiMe3 (VI), ClCH2Me2SiSiMe2CH2Cl (VII), Me2SiCl2 (VIII), MePrSiCl2 (IX), Me3SiCH2SiMeCl2 (X), Me3SiCH2CH2SiMeCl2 (XI), Me3SiCH2CH2CH2SiMeCl2 (XII), ClCH2Si(H)MeCl (XIII), ClCH2SiMe2Cl (XIV), ClMe2SiSiMe2Cl (XV), ClCH2CH2CH2Si(H)MeCl (XVI), ClCH2CH2CH2SiMe2Cl (XVII), ClCH2CH2OSiMe2Cl (XVIII), ClMe2SiCH2SiMe2Cl (XIX), ClMe2SiCH2CH2SiMe2Cl (XX), and ClMe2SiCH2CH2CH2SiMe2Cl (XXI) with K/Na alloy vapours at 0.1-1 Torr and 300-320 deg C yields products derived from the reactions of short-lived intermediates, such as silyl and silylmethyl radicals, silylenes, and sila-alkenes.In addition, small-ring silacycles of low stability are formed as the intermediates in some of the dehalogenation reactions.Combination and H-atom abstraction are the main reactions of silyl and silyl-methyl radicals.These radicals are not prone to decomposition reactions when C-H, C-C, or Si-C bonds are at the β(Si-Si) bond with the formation of Me2Si=CH2 and the trimethylsilyl radical.The generation of alkylmethylsilylenes is accompanied by their decomposition processes, which involves intramolecular β(C-H) insertion of alkylmethylsilylenes and 2+1>-thermocyclodecomposition of intermediate silacyclopropanes.The contribution of δ(C-H) and ε(C-H) insertion reactions is much less pronounced, and in the formation of five- or six-membered silacycles.We did not succeed in obtaining monosilacyclobutanes, as the intramolecular γ(C-H) insertion is not typical for silylenes with alkyl substituents.Dehalogenation of chloromethylchlorosilanes with alkali metal vapours yields sila-alkenes, and that of 1,2-dichlorodisilanes gives disilenes. 1-Methyl-1-silaethylene, obtained by this method, does not rearrange into dimethylsilene, but dimerizes to give 1,3-dimethyl-1,3-disilacyclobutane.The formation of 1,3,5-trisilacyclohexanes takes place due to subsequent radical addition at the silicon-carbon double bond and cyclization of 1,6-biradicals.Dehalogenation of organochlorosilanes XVI, XVII, and XX opens up possibilities for the gas-phase synthesis of small organosilicon heterocycles: monosilecyclobutanes and 1,2-disilacyclobutanes.A new, low-stability heterocycle, i.e. 1,1,2,2-tetramethyl-1,2-disilacyclobutane, has been obtained, which enables a new, high polymer, polyethylenetetramethyldisilene, to be obtained.In the case of organochlorosilanes XVIII and XIX, cyclization is accompanied by secondary reactions of silacycles, rearrangements, dimerization, or decomposition.
SILAETHENE I. DARSTELLUNG UND CHARAKTERISIERUNG VON MONOSILACYCLOBUTANEN
Auner, N.,Grobe, J.
, p. 25 - 52 (2007/10/02)
Monosilacyclobutanes of the type RR' are prepared by ring closure reactions of 3-halopropylhalosilanes and by substitution of SiCl containing silacyclobutane rings with organometallic reagents (RMgX, LiR, NaCp).Under optimal experimental conditions yields between 50 and 95percent can be obtained by both procedures.Characterization of the compounds is accomplished by analytical (C, H, N) and NMR, IR and mass spectroscopic investigations.
THERMAL AND PHOTOCHEMICAL BEHAVIOR OF 2-SILA- AND GERMA-CYCLOPENTANONE
Hassner, Alfred,Soderquist, John A.
, p. 429 - 432 (2007/10/02)
Pyrolysis and photolysis of the first examples of five-membered ring sila and germa ketones 2 is reported.The photolysis of 2a leading to a cyclic acetal via a siloxycarbene is contrasted to the behavior of the germa analog 2b wich gives ring cleavage via a ketene intermediate.
