40391-87-5

Upstream product

• 288-32-4 1H-imidazole 
• 58479-61-1 tert-butylchlorodiphenylsilane 
• 84960-82-7 diphenylsilylene 
• 75-65-0 tert-butyl alcohol 
• 1663-39-4 tert-Butyl acrylate 
• 775-12-2 diphenylsilane 

Downstream Products

• 141240-81-5 1,1,2-triphenylbenzo[b]silole 
• 141240-76-8 diphenyl[2-(phenylethynyl)phenyl]silane 
• 330961-51-8 tert-butoxydiphenylsilanethiol 

Relevant academic research and scientific papers

Unexpected catalytic activity of simple triethylborohydrides in the hydrosilylation of alkenes

The first example of sodium triethylborohydride-catalysed hydrosilylation of alkenes is reported. The hydrosilylation of certain alkenes, in particular styrenes, vinylsilanes and allyl glycidyl ether, with aromatic hydrosilanes proceeded in a highly regioselective manner to give Markovnikov products. It is significant that several protocols use NaHBEt3 as a reducing agent generating active catalysts in situ of other hydrosilylation reactions. An anionic mechanism of hydrosilylation is proposed.

Hydrosilane σ-Adduct Intermediates in an Adaptive Zinc-Catalyzed Cross-dehydrocoupling of Si?H and O?H Bonds

Three-coordinate PhBOX (Formula presented.) ZnR (PhBOX (Formula presented.) =phenyl-(4,4-dimethyl-oxazolinato; R=Me: 2 a, Et: 2 b) catalyzes the dehydrocoupling of primary or secondary silanes and alcohols to give silyl ethers and hydrogen, with high turnover numbers (TON; up to 107) under solvent-free conditions. Primary and secondary silanes react with small, medium, and large alcohols to give various degrees of substitution, from mono- to tri-alkoxylation, whereas tri-substituted silanes do not react with MeOH under these conditions. The effect of coordinative unsaturation on the behavior of the Zn catalyst is revealed through a dramatic variation of both rate law and experimental rate constants, which depend on the concentrations of both the alcohol and hydrosilane reactants. That is, the catalyst adapts its mechanism to access the most facile and efficient conversion. In particular, either alcohol or hydrosilane binds to the open coordination site on the PhBOX (Formula presented.) ZnOR catalyst to form a PhBOX (Formula presented.) ZnOR(HOR) complex under one set of conditions or an unprecedented σ-adduct PhBOX (Formula presented.) ZnOR(H?SiR′3) under other conditions. Saturation kinetics provide evidence for the latter species, in support of the hypothesis that σ-bond metathesis reactions involving four-centered electrocyclic 2σ–2σ transition states are preceded by σ-adducts.

Heavier Alkaline-Earth Catalyzed Dehydrocoupling of Silanes and Alcohols for the Synthesis of Metallo-Polysilylethers

The dehydrocoupling of silanes and alcohols mediated by heavier alkaline-earth catalysts, [Ae{N(SiMe3)2}2?(THF)2] (I–III) and [Ae{CH(SiMe3)2}2?(THF)2], (IV–VI) (Ae=Ca, Sr, Ba) is described. Primary, secondary, and tertiary alcohols were coupled to phenylsilane or diphenylsilane, whereas tertiary silanes are less tolerant towards bulky substrates. Some control over reaction selectivity towards mono-, di-, or tri-substituted silylether products was achieved through alteration of reaction stoichiometry, conditions, and catalyst. The ferrocenyl silylether, FeCp(C5H4SiPh(OBn)2) (2), was prepared and fully characterized from the ferrocenylsilane, FeCp(C5H4SiPhH2) (1), and benzyl alcohol using barium catalysis. Stoichiometric experiments suggested a reaction manifold involving the formation of Ae–alkoxide and hydride species, and a series of dimeric Ae–alkoxides [(Ph3CO)Ae(μ2-OCPh3)Ae(THF)] (3 a–c, Ae=Ca, Sr, Ba) were isolated and fully characterized. Mechanistic experiments suggested a complex reaction mechanism involving dimeric or polynuclear active species, whose kinetics are highly dependent on variables such as the identity and concentration of the precatalyst, silane, and alcohol. Turnover frequencies increase on descending Group 2 of the periodic table, with the barium precatalyst III displaying an apparent first-order dependence in both silane and alcohol, and an optimum catalyst loading of 3 mol % Ba, above which activity decreases. With precatalyst III in THF, ferrocene-containing poly- and oligosilylethers with ferrocene pendent to- (P1–P4) or as a constituent (P5, P6) of the main polymer chain were prepared from 1 or Fe(C5H4SiPhH2)2 (4) with diols 1,4-(HOCH2)2-(C6H4) and 1,4-(CH(CH3)OH)2-(C6H4), respectively. The resultant materials were characterized by NMR spectroscopy, gel permeation chromatography (GPC) and DOSY NMR spectroscopy, with estimated molecular weights in excess of 20,000 Da for P1 and P4. The iron centers display reversible redox behavior and thermal analysis showed P1 and P5 to be promising precursors to magnetic ceramic materials.

Dehydrogenative coupling of alcohols and carboxylic acids with hydrosilanes catalyzed by a salen-Mn(v) complex

A Mn(v)-salen complex was found to be an effective catalyst for the dehydrogenative coupling of hydroxyl groups with hydrosilane. The reaction conditions were optimized with different silanes and efficient dehydrogenative coupling was achieved by using triethoxysilane and diphenylsilane. Various alcohols and phenols and a limited number of carboxylic acids were converted into the corresponding silyl ethers and silyl esters. A range of functional groups such as chloro, nitro, methoxy, carbonyl and carbon-carbon multiple bonds are tolerated in the reaction.

POP-pincer silyl complexes of group 9: Rhodium versus iridium

9,9-Dimethyl-4,5-bis(diisopropylphosphino)xanthene (xant(P iPr2)2) derivatives RhCl{xant(P iPr2)2} (1) and IrHCl{xant(PiPr 2)[iPrPCH(Me)CH2]} (2) react with diphenylsilane and triethylsilane to give the saturated d6-compounds RhHCl(SiR3){xant(PiPr2)2} (SiR 3 = SiHPh2 (3), SiEt3 (4)) and IrHCl(SiR 3){xant(PiPr2)2} (SiR3 = SiHPh2 (5), SiEt3 (6)). Complexes 3 and 5 undergo a Cl/H position exchange process via the MH{xant(PiPr2) 2} (M = Rh (8), Ir (E)) intermediates. The rhodium complex 3 affords the square planar d8-silyl derivative Rh(SiClPh2) {xant(PiPr2)2} (7), whereas the iridium derivative 5 gives IrH2(SiClPh2){xant(PiPr 2)2} (9), which is stable. In agreement with the formation of 7, the reactions of 8 with silanes are a general method to prepare square planar d8-rhodium-silyl derivatives. Thus, the addition of triethylsilane and triphenylsilane to 8 initially leads to the dihydrides RhH2(SiR3){xant(PiPr2)2} (SiR3 = SiEt3 (10), SiPh3 (11)), which lose molecular hydrogen to afford Rh(SiR3){xant(PiPr 2)2} (SiR3 = SiEt3 (12), SiPh 3 (13)). Treatment of 7 with NaBArF4· 2H2O leads to the cationic five-coordinate d6-species [RhH{Si(OH)Ph2}{xant(PiPr2)2}] BArF4 (14) through a silylene intermediate. According to the participation of the latter in the formation of 14, this cation is an efficient catalyst precursor for the monoalcoholysis of diphenylsilane with a wide range of alcohols, reaching turnover frequencies at 50% of conversion between 4000 and 76 500 h-1. The X-ray structures of 3, 6, 7, 9, 12, and 14 are also reported.

Fast kinetics study of the reactions of transient silylenes with alcohols. Direct detection of silylene-alcohol complexes in solution

The kinetic behavior of dimethyl-, diphenyl-, and dimesitylsilylene in hexanes solution in the presence of methanol (MeOH), tert-butanol (t-BuOH), and the respective O-deuterated isotopomers has been studied, with the goal of elucidating a detailed mechanism for the formal O-H insertion reaction of transient silylenes with alcohols in solution. The data are in all cases consistent with a mechanism involving the intermediacy of the corresponding silylene-alcohol Lewis acid-base complexes, which have been detected directly for each of the SiMe2-ROL and SiPh2-ROL (L = H or D) systems that were studied. Complexation proceeds effectively irreversibly (Keq ≥ 2 x 105 M-1) and at close to the diffusion-controlled rate in these cases. In contrast, the kinetic and spectroscopic behavior observed for SiMeS2 in the presence of these alcohols indicates the SiMeS2-ROL complexes are involved as steady-state intermediates, formed reversibly and 10-100 times more slowly than is the case with SiMe2 and SiPh2. Product formation from the silylene-alcohol complexes is shown to proceed via catalytic proton transfer by a second molecule of alcohol, the rate of which exceeds that of unimolecular intracomplex H-migration in all cases, even at submillimolar alcohol concentrations. The catalytic rate constants range from 109 to 1010 M-1 s-1 for the SiMe2-ROH and SiPh2-ROH complexes, sufficiently fast that the isotope effect ranges from ca. 2.5 to close to unity for all but the SiPh2-t-BuOL complex, where it is remarkably large (kHH/kDD = 10.8 ± 2.4). The value is consistent with a mechanism for catalysis involving double proton transfer within a cyclic five-membered transition state. The isotope effects on the ratio of the rate constants for catalytic proton transfer and dissociation of the SiMeS2-MeOH and SiMeS2-t-BuOH complexes suggest that a different mechanism for catalytic proton transfer is involved in the case of the sterically hindered diarylsilylene.

Reactions of cationic PNP-supported iridium silylene complexes with polar organic substrates

Reactions of PNP-supported silylene complexes [(PNP)(H)Ir-SiRR′] [B(C6F5)4] (R = R′ = Ph (1) and R = H, R′ = Mes (2)) with Lewis bases, carbonyl compounds, alcohols, and amines were investigated. Addition of DMAP (4-dimethylaminopyridine) to 1 and 2 produced base-stabilized silylene complexes [(PNP)(H)IrSiRR′(DMAP)] [B(C6F5)4] (R = R′ = Ph (3) and R = H, R′ = Mes (4)). Reactions of 2 with benzophenone and benzaldehyde afforded the products of stoichiometric hydrosilylation, heteroatom-substituted silylene complexes [(PNP)(H)Ir-SiMes(OCH(Ph)(R))][B(C6F5) 4] (R = Ph (5) and R = H (6)). Complex 1 reacted with DMF or benzophenone, and 2 reacted with DMF, to afford base-stabilized silylene complexes of the type [(PNP)(H)IrSiRR′(B)][B(C6F 5)4] (R = H, R′ = Mes, B = DMF (7); R = R′ = Ph, B = DMF (8) and O-CPh2 (9)). In contrast, treatment of 1 with acetophenone afforded {(PNPH)IrH[SiPh2(OC(-CH2)Ph)]} [B(C6F5)4] (10), from activation of a C-H bond at the α-carbon position of acetophenone. Reactions of alcohols and amines with 1 afforded [(PNPH)IrH(SiPh2OR)][B(C6F 5)4] (R = 3,5-tBu2C 6H3 (11), R = Ph (12), R = iPr (13), and R = tBu (14)) and [(PNPH)IrH(SiPh2NHR)][B(C6F 5)4] (R = Ph (15), R = 3,5-(CF3) 2C6H3 (16)). Exploration of the catalytic activity of iridium silylene complexes with these organic substrates demonstrated that 1 is an effective catalyst for silane alcoholysis and aminolysis and for the hydrosilylation of ketones.

2'-fluorofuranosyl derivatives and novel method of preparing 2'-fluoropyrimidine and 2'-fluoropurine nucleosides

A compound has the formula STR1 wherein R is selected from the group consisting of (C7 -C20)aroyl, (C6 -C20)aryl, aralkyl and alkylaryl, and (C1 -C10)alkyl-di(C6 -C20)aryl Si, R' is selected from the group consisting of (C1 -C10)alkyl, (C7 -C20)aroyl and (C2 -C12)acyl, all of which may be further substituted with O, S, N or alkyl, and R'" is selected from the group consisting of halogen, (C1 -C10)alkoxy, (C1 -C10)acyloxy, O-methane-sulfonyl and O-p-toluenesulfonyl. A composition of matter comprises 0.001 to 99.999 wt % of the above compound.

Conversion of hydrosilanes to alkoxysilanes catalyzed by Cp2TiCl2/nBuLi

The combination of Cp2TiCl2 and nBuLi provides an effective catalyst for alcoholysis of the model silanes n-HexSiH3, PhMeSiH2, Ph2SiH2 and PhMe2SiH by ethanol, isopropanol, t-butyl alcohol and phenol.Increasing the steric bulk of the substituents on either the alcohol or the silane generally requires longer reaction periods and/or increasing temperature.All SiH bonds are converted to SiOEt groups by ethanol and a single SiH bond in secondary silanes and two SiH bonds in tertiary silanes are replaced by t-butyl alcohol.Diols including pinacol, 2,4-pentanediol and 2,5-hexanediol react with PhRSiH2 (R = Me, Ph) to give 1,3-dioxa-2-silacyclopentanes, -hexanes and -heptanes, respectively.Attempts to form caged structures by condensation of primary silanes and triols was unsuccessful.Hydrolysis of PhRSiH2 is promoted by Cp2TiCl2/n-BuLi and the siloxane is produced in quantitative yield when R = Ph and a mixture of linear disiloxanes and trisiloxanes in addition to cyclopolysilanes are produced when R = Me.Other protic reagents including acids, mercaptans, amines and enolizable ketones did not react.The effects of reaction parameters such as temperature, silane to catalyst ratio, solvent, transition metal and replacements for nBuLi were also determined.

TRICYCLIC HETEROCYCLES WITH BIFUNCTIONAL SILICON CENTERS

Condensation of the diorganometallic reagents, (o-MC6H4)2X (M = Li, MgCl) with HSiCl3 followed by reduction with LiAlH4 provides dibenzosilacycles, I (a, X = -; b, X = NMe; c, X = CH2; d, X = CH2CH2) with two exocyclic H-substituents, =SiH2.Conditions for the stepwise conversion of I to mixed bifunctional systems, =SiHX (II, X = Cl, Br; III, X = OR), and bifunctional derivatives, =SiX2 (IV, X = Cl; V, X = OR) were determined.Controlled halogenation of I to II was accomplished with one molar equivalent of SO2Cl2 or NBS although CCl4 in the presence of ClRh(PPh3)3 or PdCl2 results in slow monochlorination.The reaction of I with excess SOCl2 or SO2Cl2 converts I to III but the latter is faster and provides fewer side reactions.Conversion of I to IV with excess alcohols occurs in high yield with ClRh(PPh3)3 but in low yield with H2PtCl6.Controlled alcoholysis of I to III could not be achieved except with tBuOH.The dichlorides, IV, are methylated in high yield to VII, =SiMe2.Reaction of Ib with ClRh(PPh3)3 results in elimination of H2 and formation of disilanes as indicated by trapping reactions with alcohols (formation of Vb).