121386-64-9Relevant academic research and scientific papers
Synthesis and fluoride-promoted Wittig rearrangements of α-alkoxysilanes
Maleczka Jr., Robert E.,Geng, Feng
, p. 1111 - 1113 (2008/02/09)
(matrix presented) Lewis acid-catalyzed reaction of allyl and benzyl trichloroacetimidates with α-silyl alcohols was found to be a general method for the synthesis of α-alkoxysilanes. Upon exposure to CsF, these α-alkoxysilanes could be made to undergo [2,3]-Wittig rearrangement with an efficiency similar to that realized by the analogous but inherently more toxic α-alkoxystannanes.
THE ASYMMETRIC HYDROBORATION OF SIMPLE ALKENYLSILANES: CHIRAL α-SILYLALKYL-BORANES AND ALCOHOLS
Soderquist, John A.,Lee, Shwn-Ji Hwang
, p. 4033 - 4042 (2007/10/02)
The detailed study of the asymmetric hydroboration of various vinylsilanes with monoisopinocampheylborane (IPCBH2) is presented.In all cases, β substitution on the vinylsilane gives monomeric dialkylborane adducts with the boryl group α to the silicon.These studies shown that the larger the groups on silicon are, the more positive the influence on the enatioselectivity of the process.Moderate asymmetric induction (24-40percent) is observed only for vinyl silanes wich contain a substituent trans to the silicon.A model for the asymmetric hydroboration of alkenes with this reagent is proposed.The complete charactarization of the borane intermediates was achieved employing NMR (11B, 13C, 1H, 29Si).
Reduction of Halosilanes by Organotin Hydrides
Wilt, James W.,Belmonte, Frank G.,Zieske, Paul A.
, p. 5665 - 5675 (2007/10/02)
A study of the reduction of halosilanes with organotin hydrides is described.The free radical chain mechanism indicated by the results obtained parallels that known for the comparable reduction of haloalkanes, but the reactivity of α-haloalkanes is considerable enhanced.Mechanistic studies suggest that the polar nature of the halogen abstraction step in the radical chain sequence, which places incremental negative charge adjacent to silicon, is the principal reason for this enhanced reactivity.Structure-reactivity studies indicat the gem-dimethylsilyl function to be an electronic transmitter.The ρ values for reduction of aryldimethyl(chloromethyl)silanes and substituted benzyl chlorides by tri-n-butyltin hydride are essentially identical (+0.45).Reduction of (chloromethyl)trimethylsiulane with aryldimethyltin hydrides, conversely, yielded a ρ value of -1.61.The reduction produced racemic product from an optically active α-chlorosilane, the synthesis of which appears to the first reported.Other syntheses of variuos halosilanes of interest are also described.The title reduction is specific for carbon-halogen bonds.Silicon-halogen bonds are not affected, a distinction that should make the reduction synthetically useful.Because the increased reactivity of α-halosilanes in the reduction has thus been ascribed to a kinetic polar effect in a critical step of the mechanism, no compelling argument for special thermodynamic stability in α-silyl radicals themselves can be made.
Hydroboration. 56. Convenient and Regiospecific Route to Functionalized Organosilanes through the Hydroboration of Alkenylsilanes.
Soderquist, John A.,Brown, Herbert C.
, p. 3571 - 3578 (2007/10/02)
A systematic and detailed study of the hydroboration of several representative alkenylsilanes is reported.By use of a 1:1 molar stoichiometry, the hydroboration of vinyltrimethylsilane (1) at 0 deg C with BH3*THF gives a mixture of dialkylborane products exclusively with a ca. 60:40 distribution of a α- and β-silylethyl groups in these adducts.Redistribution of the reaction mixture at a somewhat higher temperature (50 deg C) gives the corresponding monoalkylboranes.The redistribution process is regiospecific, leaving the original 60:40 ratio of α- and β-silylethyl groups in the dialkylboranes unchanged in the monoalkylboranes produced.With a 3:1 ratio of 1 to BH3*THF, equimolar amounts of dialkyl- and trialkylborane products are formed in the hydroboration reaction.Under these conditions, the α to β ratio changes modestly to 50:50.The failure of the hydroboration to attain complete conversion to the trialkylborane stage is attributed largely to the low reactivity of meso-bisborane produced in the reaction in the further hydroboration of 1.The change in the regioselectivity from 60:40 to 50:50 with a 3:1 stoichiometry is attributed to the higher β selectivity of dialkylboranes in the hydroborationof 1.Thus, the hydroboration of 1 with 9-borabicyclononane (9-BBN) is regiospecific, giving exclusively the B--9-borabicyclononane (3) product.Redistribution of 3 with BH3*THF gives essentially complete conversion to 9-BBN and pure bisborane.This compound hydroborates 1 rapidly at 0 deg C, giving predominantly (ca. 85percent) the β adduct, trisborane.Hydroboration of propen-2-yltrimethylsilane with BH3*THF gives primarily (91percent) β boron placement.However, use of 9-BBN eliminates the formation of the minor internal product and gives (2-Me3Si-1-Pr)-9-BBN exclusively.Hydroboration of cis-1-propenyltrimethylsilane (17) with BH3*THF proceeds to the dialkylborane stage, with no significant formation of the corresponding trialkylborane.The hydroboration is highly regioselective, giving the bisborane product in 95percent regioisomeric purity.This borane is unusual in that it is monomeric in solution, as revealed by IR and 11B NMR data.Hydroboration of 17 with 9-BBN is much less selective than that with BH3*THF, a rare occurrence, giving essentially equal amounts of regioisomeric adducts.Hydroboration of allyltrimethylsilane with either BH3*THF or 9-BBN gives the (γ-silylpropyl)borane product exclusively.Hydroboration of 3-buten-1-yltrimethylsilane with BH3*THF gives the (δ-silylbutyl)borane adduct in 94percent isomeric purity.With 9-BBN, the hydroboration is regiospecific, giving the (δ-silylbutyl)borane adduct exclusively.Thus, through hydroboration, the syntheses of α, β, γ, and δ boron-functionalized organosilanes are achieved, making such compounds available for use as synthetic intermediates.The 13C and 11B spectra...
