Allyltrimethylsilane Research Articles

Plasma polymerization of allyltrimethylsilane with single‐filament dielectric‐barrier discharges—Evidence of cationic surface processes

AbstractAtmospheric‐pressure plasma‐enhanced film deposition with single‐filament dielectric‐barrier discharges (DBDs) in argon was investigated using allyltrimethylsilane (ATMS) as a precursor. Nonionic deposition in the discharge zone is largely precluded by a rapid cross‐flow of the source gas, containing between 50 and 2000 ppm of ATMS. The performed experimental studies show a surprisingly large deposited film mass per transferred elementary charge between 220 and 540 amu. Film growth experiments, mass‐spectrometric studies, and kinetic considerations led to the conclusion that the deposition process is a cationic surface polymerization, initiated by ions produced in the DBD by energy transfer from long‐lived excited Ar species and propagated by addition of ATMS monomer molecules.

Pre-electrolysis of LiClO4 in Acetonitrile: Electrochemically Induced Protolytic Carbon-Carbon Bond Formation of Benzylic Ethers and Acetals with Allyl Trimethylsilane and Other Carbon Nucleophiles.

The pre-electrolysis of LiClO4 in acetonitrile in an undivided cell applying only "catalytic" amounts of current (e.g., 0.05 F) led to the formation of a strong acidic medium for the activation of benzylic ethers and acetals. The activated primary and secondary benzylic ethers and acetals could be converted with a range of carbon nucleophiles, such as allyl trimethylsilane, silyl enol ethers, and enol acetates, for the formation of new carbon-carbon bonds. A chemoselective reaction was observed when electron-deficient benzylic acetals were converted with allyl trimethylsilane to the monoallylated products, whereas an electron-rich benzylic acetal led to the double allylated product under activation of both ether groups.

Characterization and Fate of a Septanosyl Ferrier Cation in the Gas and Solution Phases.

Ferrier reactions follow a mechanistic pathway whereby Lewis acid activation of a cyclic enol ether facilitates departure of an allylic leaving group to form a glycosyl Ferrier cation. Attack on the Ferrier cation provides a new acetal linkage concurrent with the transposition of the alkene moiety. The idiosyncratic outcomes of Ferrier reactions of seven-membered ring carbohydrate-based oxepines prompted an investigation of its corresponding septanosyl Ferrier cation. Experiments that characterized the ion, including gas-phase cryogenic IR spectroscopy matched with density functional theory-calculated spectra of candidate cation structures, as well as product analysis from solution-phase Ferrier reactions, are reported here. Results from both approaches revealed an inclination of the seven-membered ring cation to contract to five-membered ring structures. Gas-phase IR spectra matched best to calculated spectra of structures in which five-membered dioxolenium formation opened the oxepine ring. In the solution phase, an attack on the ion by water led to an acyclic enal that cyclized to a C-methylene-aldehydo arabinofuranoside species. Attack by allyl trimethylsilane, on the other hand, was diastereoselective and yielded a C-allyl septanoside.

N‐(Morpholine‐4‐dithio)phthalimide: A Shelf‐Stable, Bilateral Platform Molecule Enabling Access to Diverse Unsymmetrical Disulfides**

AbstractSynthetic methods for unsymmetrical disulfides are greatly needed owing to their applications in drug discovery, linker chemistry, and materials sciences. In this study, a new shelf‐stable and easy‐to‐prepare bilateral disulfurating platform molecule, N‐(morpholine‐4‐dithio)phthalimide, has been developed for the divergent synthesis of unsymmetrical disulfides. The amino and imide leaving groups of this reagent can be orthogonally transformed. Under acidic conditions, the amino moiety undergoes selective protonation and thus can be displaced by various carbon nucleophiles, such as allyl trimethylsilanes, alkynyl silanes, and electron‐rich arenes, leaving the phthalimide moiety untouched. Meanwhile, the phthalimide leaving group is amenable to substitution under basic or neutral conditions. The combination of these transformations provides rapid access to diverse unsymmetrical disulfides through two C−S bond‐forming reactions.

N-(Morpholine-4-dithio)phthalimide: A Shelf-Stable, Bilateral Platform Molecule Enabling Access to Diverse Unsymmetrical Disulfides.

Synthetic methods for unsymmetrical disulfides are greatly needed owing to their applications in drug discovery, linker chemistry, and materials sciences. In this study, a new shelf-stable and easy-to-prepare bilateral disulfurating platform molecule, N-(morpholine-4-dithio)phthalimide, has been developed for the divergent synthesis of unsymmetrical disulfides. The amino and imide leaving groups of this reagent can be orthogonally transformed. Under acidic conditions, the amino moiety undergoes selective protonation and thus can be displaced by various carbon nucleophiles, such as allyl trimethylsilanes, alkynyl silanes, and electron-rich arenes, leaving the phthalimide moiety untouched. Meanwhile, the phthalimide leaving group is amenable to substitution under basic or neutral conditions. The combination of these transformations provides rapid access to diverse unsymmetrical disulfides through two C-S bond-forming reactions.

Silylium-Catalyzed Regio- and Stereoselective Carbosilylation of Ynamides with Allylic Trimethylsilanes.

The regio- and stereoselective carbosilylation of tosylynamides with allylic trimethylsilanes takes place under mild conditions in the presence of catalytic TMSNTf2 or HNTf2 to give (Z)-α-allyl-β-trimethylsilylenamides with good yields. Theoretical calculations show the activation of the C-C triple bond of the ynamides by the trimethylsilylium ion and formation of a β-trimethylsilylketenimonium cation. Further transformations of the products demonstrate the synthetic utility of this reaction.

Three-Component Reaction of Pentafluorosulfanyl Chloride, Alkenes and Diazo Compounds and Synthesis of Pentafluorosulfanylfurans.

We report herein the three-component radical addition reaction of SF5 Cl, alkene and diazo compounds for the selective formation of α-alkyl-α-SF5 carbonyl compounds. The three-component addition reaction proceeded through the first reaction of SF5 radical with the diazo compound followed by the addition of the in situ generated carbon radical to alkene. The synthetic useful α-allyl-α-SF5 carbonyl compounds were successfully prepared when allyl trimethylsilanes were used as the alkene substrates. Furthermore, the three-component adducts formed from SF5 Cl, α-diazoacetophenones and vinyl acetates were converted into pentafluorosulfanylfurans. This transformation provided a practical and efficeint method for the synthesis of pentafluorosulfanylfurans.

Three‐Component Reaction of Pentafluorosulfanyl Chloride, Alkenes and Diazo Compounds and Synthesis of Pentafluorosulfanylfurans

AbstractWe report herein the three‐component radical addition reaction of SF5Cl, alkene and diazo compounds for the selective formation of α‐alkyl‐α‐SF5 carbonyl compounds. The three‐component addition reaction proceeded through the first reaction of SF5 radical with the diazo compound followed by the addition of the in situ generated carbon radical to alkene. The synthetic useful α‐allyl‐α‐SF5 carbonyl compounds were successfully prepared when allyl trimethylsilanes were used as the alkene substrates. Furthermore, the three‐component adducts formed from SF5Cl, α‐diazoacetophenones and vinyl acetates were converted into pentafluorosulfanylfurans. This transformation provided a practical and efficeint method for the synthesis of pentafluorosulfanylfurans.

Structural Investigation of Photochemical Intermediates in Solution by Cold UV Spectroscopy in the Gas Phase: Photosubstitution of Dicyanobenzenes by Allylsilanes

Electrospray ion sources with an in-line quartz cell were constructed to produce photochemical intermediates in solution. These ion sources can detect photochemical intermediates having lifetimes longer than a few seconds. Intermediates formed by photosubstitution of 1,4-dicyanobenzene (DCB) by allyltrimethylsilane (AMS) in acetonitrile using a Xe lamp were injected into the mass spectrometer. The cationic intermediate (C11H10N2·H+) was observed at m/z = 171, but no anionic intermediate was found, although C11H9N2- was expected based on prior studies. Theoretical studies suggested that C11H9N2- was simultaneously converted to neutral C11H10N2 and cationic C11H10N2·H+ species, which can be stable intermediates in the photosubstitution reaction. The UV photodissociation (UVPD) spectrum of C11H10N2·H+ under cold (∼10 K) gas-phase conditions determined the conformation of the C11H10N2 unit of the C11H10N2·H+ cation. This report demonstrates that cold gas-phase UV spectroscopy is a prospectively powerful tool for investigation of the electronic and geometric structures of photochemical intermediates produced in solution.

Development of Poly(methyl methacrylate)-Based Copolymers with Improved Heat Resistance and Reduced Moisture Absorption

Poly(methyl methacrylate) (PMMA) is widely used as a transparent material for optical applications, owing to its high light transmittance. However, it exhibits poor heat resistance and high moisture absorption, leading to distortion and deformation upon exposure to elevated temperatures and/or moisture. These structural changes decrease the transparency of PMMA, critically limiting its applicability. In this study, we synthesized poly(methyl methacrylate-co-styrene-co-acrylamide) (PMSAm) as a reference polymer and introduced one of four different comonomers [N-phenylmaleimide (PMI), N-cyclohexylmaleimide (CHMI), allyltrimethylsilane (ATMS), or 2,2,2-trifluoroethyl methacrylate (TF)] as a means to improve heat resistance and reduce moisture absorption. Four series of PMMA-based random copolymers (PMSAm-PMI, PMSAm-CHMI, PMSAm-ATMS, and PMSAm-TF) were synthesized by conventional thermal radical polymerization. All of the polymers synthesized exhibited improved heat resistance, with PMSAm-CHMI exhibiting the highest glass transition temperature (Tg = 122.54 °C) and 5% weight loss thermal decomposition temperature (T5d = 343.40 °C) as well as the lowest thermal expansion coefficient (90.3 μm m-1 °C-1). The highest hydrophobicity was exhibited by PMSAm-TF, with a water contact angle of 78.9°, indicating higher hydrophobicity compared to that of pure PMMA (69.4°). More importantly, high transparency (∼90%) was exhibited by all of the synthesized polymers. Thus, our copolymerization strategy successfully addresses the limitations, i.e., low heat resistance and high moisture absorption, of conventional PMMA-based materials.

Cis-Specific Chain Transfer Ring-Opening Metathesis Polymerization Using a Vanadium(V) Alkylidene Catalyst for Efficient Synthesis of End-Functionalized Polymers

Highly efficient synthesis of end-functionalized polymers has been achieved by combined cis-specific ring-opening metathesis polymerization (ROMP) of norbornene with terminal olefins (1-hexene, allyltrimethylsilane (ATMS), etc.) as the chain transfer (cross metathesis) agent at 80 °C in the presence of V(CHSiMe3)(N-2,6-Cl2C6H3)[OC(CF3)3](PMe3)2. The ROMP proceeds with high activity and high cis selectivity (97–98%) upon addition of PMe3, and the Mn values could be controlled by varying the concentration of terminal olefins; the activity at 80 °C was not affected by the ATMS concentrations (5.0–50.0 mol %, TOF 1860–1890 min–1 ((1.12–1.13) × 105 h–1)).

PhI(OCOCF3)2-catalyzed nucleophilic substitution of aromatic propargyl alcohols

Hypervalent [bis(trifluoroacetoxy)iodo]benzene (PIFA) is shown to behave as a Lewis acid for the nucleophilic substitution of propargylic alcohols with diverse C-, O-, S-, and N-nucleophiles without the synergistic assistance of other acid activators or stoichiometric oxidants, while fully demonstrating a complementary utility of oxidative hypervalent iodine(III) in terms of its high reactivity in the coupling reactions of propargyl alcohols with allyl trimethylsilane and electron-rich arenes. A propargylic carbocation generated by a reversible equilibrium between the reaction substrates and PIFA catalyst is involved in the reaction mechanism as revealed by the reaction parameters and control experiments.

Ruthenium catalyzed synthesis of 2,3-unsaturated C-glycosides from glycals

A highly efficient and convenient C-glycosylation method was developed using ruthenium(III) chloride for the synthesis of 2,3-unsaturated C-glycosides. Various nucleophiles such as allyl trimethylsilane, triethylsilane, trimethylsilyl cyanide, trimethylsilyl azide and heterocycles such as thiophene and furan reacted smoothly with glycals in the presence of catalytic amount of ruthenium trichloride under mild reaction conditions.

Highly robust SiCOH/mesoporous SiO2 ultralow dielectric films with heterostructures

We report here a new dual-coating method for the deposition of SiCOH (elementally descriptive but not representing the stoichiometry) ATMS (allyltrimethylsilane) low-k films on mesoporous SiO2 (SBA-15)/PEG (polyethylene glycol) composite films to improve the dielectric constant and mechanical properties of SiCOH/SBA-15 dual forms.

First total synthesis of Debilisone C

Total synthesis of Debilisone C, a lactone containing conjugated endiyne has been achieved. The adopted strategy involves the stereoselective construction of the five membered lactone ring and the C20 endiyne chain followed by regioselective coupling of both the parts. The lactone was obtained from the oxidative cleavage of the hydroxy olefin which was derived from the benzyl protected S-epichlorohydrine by regioselective epoxide opening with allyl trimethyl silane in presence of a Lewis acid at -78 °C. Takai olefination, Pd(0)/Ag(1) catalyzed cross-coupling reaction and selective substitution of trimethylsilyl groups were successfully utilized to establish the C20 polyyne chain. The final coupling of both the parts have been carried out by alkyl coupling using LDA in THF-DMPU (1 : 1).

Nanoporous SiCOH/CxHy dual phase films with an ultralow dielectric constant and a high Young's modulus

We used plasma-enhanced chemical vapor deposition (PECVD) of allyltrimethylsilane (ATMS), consisting of an allyl group along with three methyl groups attached to silicon, to form a low dielectric constant (low-k) and high modulus SiCOH matrix. We found that the dielectric constant and mechanical properties of the low-k material are strongly affected by the selection of the precursor, processing conditions such as the deposition temperature and post-treatment, the introduction of a second labile phase, and the chemical structure and composition of the films. After porogen (pore generator) treatment with cyclohexene oxide (CHO), the resulting material exhibited a low dielectric constant with excellent mechanical and thermal properties, having k ∼ 2.4 and a Young's modulus of 8.4 GPa. FT-IR and XPS results show that this is caused by the desorption of the labile phase (CxHy), the formation of Si–O cage-like structures, and changes in the chemical composition of films after thermal treatment. SiO2, SiO3, and SiO4 impart greater modulus and hardness to the films by increasing the stable component of Si–O in the SiCOH matrix.

Syndiotactic Polyallyltrimethylsilane-Based Stereoregular Diblock Copolymers: Syntheses and Self-Assembled Nanostructures

Structurally well-defined stereoregular diblock copolymers composed of syndiotactic polyallyltrimethylsilane (sPATMS) and poly(methyl methacrylate) (PMMA) were prepared by using an α-bromoester-terminated sPATMS macroinitiator, which was chain extended by MMA using a cuprous halide-based atom transfer radical polymerization (ATRP) system. The α-bromoester-terminated sPATMS macroinitiator was prepared via the esterfication of hydroxyl-capped sPATMS with α-bromoisobutyryl bromide. The hydroxyl-capped sPATMS was generated via a selective chain transfer reaction to triethylaluminum (TEA) during the syndiospecific polymerization of allyltrimethylsilane (ATMS) conducted in the presence of syndiospecific ansa-metallocene catalysts. The proposed synthetic route not only offers the high-yield production of stereoregular sPATMS-b-PMMA but also provides the linking of the stereoregular block (sPATMS) with PMMA through a controlled/living radical polymerization process. Moreover, the proposed method offers effective control over the block chain length, the molecular weight distribution (Mw/Mn) and the stereoregularity of sPATMS block. Thus, the self-assembly of the resultant diblock copolymers produces well-ordered nanostructures from microphase separation, as evidenced by transmission electron microscopy and small-angle X-ray scattering results.

ATRP–RCMpolymercyclization: synthesis of amphiphilic cyclic polystyrene-b-poly(ethylene oxide) copolymers

A novel amphiphilic block copolymer, i.e., cyclic polystyrene-b-poly(ethylene oxide) (cyclic PS-b-PEO 2), was synthesized through atom-transfer radical polymerization (ATRP), followed by ring-closing metathesis (RCM). Thus, a bromobenzyl-terminated PS-b-PEO-b-PS (6) was first prepared by ATRP of styrene using a PEO macroinitiator having 2-bromoisobutyryl groups (5). The subsequent end-group conversion into allyl groups was performed quantitatively with allyltrimethylsilane (ATMS) in the presence of TiCl4. The allyl-telechelic triblock copolymer PS-b-PEO-b-PS (7) thus obtained was subjected to metathesis polymer cyclization with a Grubbs' 2nd generation catalyst to produce amphiphilic cyclic PS-b-PEO (2).

Synthesis of rodocaine

A new method for synthesis of rodocaine ( 1) is presented. Two key steps were carried out by the N-bromosuccinimide (NBS)-mediated intermolecular addition of known enamine 5 with allyltrimethyl silane in presence of boron trifluoride etherate (BF 3/OEt 2) and the intramolecular ring-closing metathesis of triene 3. The Diels–Alder cycloaddition of triene 3 with different ethyl propiolates was also studied.

Regioselective reactions of sulfur, selenium and tellurium chlorides with allyl trimethyl silane

Electrophilic addition of SCl 2, SeCl 2 and SeCl 4 to 2 equivalents of allyl trimethyl silane proceeds regioselectively to give bis[2-chloro-3-(trimethylsilyl)propyl] sulfide, selenide and selenium dichloride, respectively. The reaction with TeCl 4 affords only diallyl tellurium dichloride. The structures of the compounds were confirmed by 1H, 13C, 77Se and 125Te NMR techniques.