Allyltrimethylsilane Research Articles

ChemInform Abstract: 2-(Trimethylsilylmethyl)allyl Trimethylsilane, Precursor of Methylene Carbocycles and Heterocycles.

ChemInform Abstract: 2-(Trimethylsilylmethyl)allyl Trimethylsilane, Precursor of Methylene Carbocycles and Heterocycles.

First Enantioselective Total Synthesis of the Reported Structure of (R)-(+)-Orizaterpenyl Benzoate Using an Asymmetric Allylation of a Prochiral Ketone in a Domino Process

An efficient synthesis of (R)-orizaterpenyl benzoate using a multicomponent domino allylation reaction of a prochiral ketone with allyltrimethyl silane and the enantiopure silyl ether of benzyl phenyl carbinol in the presence of catalytic amounts of TfOH is described.

Cobalt-Catalyzed 1,4-Hydrovinylation of Allylsilane and Allylboronic Esters for the Synthesis of Hydroxy-Functionalized 1,4-Dienes

The cobalt(I)-catalyzed 1,4-hydrovinylation reaction of allyl trimethylsilane and allyl pinacol boronic ester with symmetrical and unsymmetrical 1,3-dienes generates building blocks for the in situ allylboration or the Lewis acid induced allylation reaction utilizing the corresponding allyl silane derivatives. The products of these three-component reactions are hydroxy-functionalized 1,4-dienes which can be used for the synthesis of pyranones. An alternate reaction sequence for the synthesis of the hydroxy-functionalized 1,4-dienes by performing the allylation first followed by the cobalt-catalyzed 1,4-hydrovinylation is also possible. Accordingly, polyfunctionalized complex structures can be generated by both approaches in a convergent fashion.

Iodine‐Catalyzed Highly Diastereoselective Synthesis of trans‐2,6‐Disubstituted‐3,4‐Dihydropyrans: Application to Concise Construction of C28–C37 Bicyclic Core of (+)‐Sorangicin A

A novel iodine-catalyzed highly diastereoselective synthesis of trans-2,6-disubstituted-3,4-dihydropyrans have been achieved from delta-hydroxy alpha,beta-unsaturated aldehydes by treating with allyltrimethyl silane in THF at room temperature with good to excellent yields. This methodology has been successfully implemented for a concise asymmetric synthesis of C28-C37 dioxabicyclo[3.2.1]octane ring system of (+)-sorangicin A in 8 steps with 21% overall yield.

Structure−Reactivity Scales in Carbocationic Polymerizations: The Case of α-Methylstyrene

The propagation rate constant, kp, for the cationic polymerization of α-methylstyrene (αMeSt) was determined. First, the polymerization of αMeSt was carried out initiated by the diαMeStHCl/SnBr4 initiator/coinitiator system in dichloromethane (DCM) or in DCM/methylcyclohexane (MeCHx) 1:1 (v/v) solvent mixture at −80 °C in the presence of allyltrimethylsilane (ATMS). Clean and quantitative addition of ATMS to the propagating end terminates the polymerization, and from the limiting conversion and molecular weights, the kp/kATMS ratio was calculated. The kp = (5.2 and 7.7) × 107 L mol−1s−1 in DCM and DCM/MeCHx 1:1 (v/v), respectively, were calculated from the kATMS values determined by the diffusion clock method. Competition polymerizations between αMeSt and each of the following monomers p-methylstyrene (pMeSt), isobutylene (IB), styrene (St), and p-chlorostyrene (pClSt) were performed in DCM/MeCHx 1:1 (v/v) at −80 °C. From the limiting conversions and molecular weights, the reactivity ratios kp/k12 were de...

Fluorescent Spherical Particle Formation from Solid Polysilanes by the Aid of Laser Ablation and Photochemical Reaction

With the aid of laser ablation using the third harmonic of Nd:YAG laser light, spherical fine particles were produced from poly(dimethylsilane) (PDMS) powder and poly(methylphenylsilane-co-diphenylsilane) (P(MPS-co-DPS)) powder in the atmosphere of allyltrimethylsilane (ATMeSi). The particle size and the product yield of laser-ablated PDMS/ ATMeSi particles increased with increasing vapor pressure of ATMeSi, suggest- ing that ATMeSi reacted with silyl radical end of polysilane chain and during the poly- merization reaction of ATMeSi, it reacted with silyl radical end of another polymer chain to extend the particle size. Laser-ablated PDMS/ATMeSi particles emitted fluorescence at shorter wavelengths than PDMS powder without laser ablation. With increasing vapor pressure of ATMeSi, fluorescence peak shifted to shorter wavelengths, indicating that recombination of polymer silyl radicals was inhibited by the reaction with ATMeSi, and hence the average length of polysilane chains became shorter. Laser-ablated P(MPS-co- DPS)/ATMeSi particles also emitted fluorescence. In addition to a narrow band observed at 368 nm, a broad band was observed at ∼485 nm due to branching of polysilane chain. Chemical processes to form branched polymer chain were discussed briefly.

Stereocontrolled Generation of the (2R) Chroman Core of Vitamin E: Total Synthesis of (2R,4′RS,8′RS)-α-Tocopherol

(2R,4'RS,8'RS)-alpha-tocopherol (1) was prepared using, as the two key steps, a novel diastereoselective TiCl(4)-promoted (S)-sulfoxide-directed allylation of ketal 2 with allyl trimethyl silane 3 to efficiently generate the challenging (2R) stereocenter of the chroman moiety and a cross-metathesis reaction with olefin 4 to efficiently join the lipophilic alkyl chain present in the final target.

The Domino Multicomponent Allylation Reaction for the Stereoselective Synthesis of Homoallylic Alcohols

Stereoselective allylations of carbonyl compounds such as aldehydes and ketones are useful but challenging reactions in organic chemistry. The resulting chiral secondary and tertiary homoallylic alcohols or ethers are valuable building blocks in the synthesis of biologically active natural compounds and pharmaceuticals. Although researchers have developed several methods for the facially selective allylation of aldehydes, the stereoselective allylation of ketones still poses a severe problem. We have developed a highly diastereoselective domino multicomponent allylation reaction of a ketone and allyltrimethyl silane using the trimethylsilyl ether of a norpseudoephedrine or mandelic acid derivative as an auxiliary with a diastereoselectivity of up to 98:2. The reaction is performed at -78 degrees C in the presence of a catalytic amount of trifluoromethanesulfonic acid and leads to the corresponding tertiary ethers. The procedure can also be used for the allylation of aliphatic aldehydes with a diastereomeric ratio >99:1. Ketones give the 4,1'-syn product while the aldehydes give the reversed selectivity to yield a 4,1'-anti product. In addition, the reaction of gamma-substituted allyl silanes with ketones yields a product with two stereogenic centers and an anti diastereoselectivity of >99:1. The homoallylic ethers formed in the domino multicomponent process can be used in further synthetic transformations: the auxiliary can serve as a protecting group or can be cleaved reductively to give the corresponding homoallylic alcohols. Based on a number of both experimental and theoretical studies of the reaction mechanism, we conclude that an intermediate oxocarbenium ion is formed in the reaction of ketones. The oxocarbenium ion is attacked by the allyl silane during the stereogenic step. Using density functional theory methods, we could trace the observed stereoselectivity phenomena back to open transition states (TSs) where there is no interaction between the silane's trimethylsilyl group and the former carbonyl oxygen. On the contrary, the reaction with aldehydes forms an intermediate oxazolidinium salt, which explains the opposite selectivity. We have used the new allylation procedure in several total syntheses of natural products such as vitamin E, (+)-hydroxymyoporone, 5,6-dihydrocineromycin B, and polyoxygenated cembrenes.

Mild and Highly Efficient Stereoselective Synthesis of 2,3‐Unsaturated Glycopyranosides using La(NO3)3 · 6H2O as a Catalyst: Ferrier Rearrangement

A mild and highly efficient stereoselective reaction of 3,4,6‐tri‐O‐acetyl‐d‐glucal with a variety of nucleophiles, viz. alcohols, phenols, thiols, thiophenols, and allyl trimethyl silane (TMS), in the presence of 5 mol% of lanthanum(III) nitrate hexahydrate under solvent‐free conditions yielded the corresponding 2,3‐unsaturated glycopyranosides (pseudoglycals) in excellent yields.

Deposition and Characterization of Dielectric Thin Films from Allyltrimethylsilane Glow Discharges

AbstractThin films with a dielectric constant in the range of 1.9–4.5 have been deposited under different experimental conditions from allyltrimethylsilane (ATMS) and oxygen fed glow discharges. The thermal stability of the coatings is evaluated from thickness loss during the annealing process at 400 and 450 °C. Extremely low values of dielectric constant can be obtained at low input power and oxygen flow rate. However, control over the annealing temperature must be gained in order to avoid excessive film matrix collapse with subsequent deterioration of dielectric properties. For the lowest dielectric constant of 1.9, thickness shrinkage of 11% has been detected. Deposition temperature is also found to strongly affect film dielectric constant and chemical composition while input power modulation does not improve the dielectric properties of the films.magnified image

A General and Efficient FeCl3‐Catalyzed Nucleophilic Substitution of Propargylic Alcohols.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Gas Phase Synthesis of Linearly Aggregated Cobalt-Containing Organosilicon Fine Particles

A gaseous mixture of cobalt tricarbonyl nitrosyl (Co(CO)3NO) and allyltrimethylsilane (ATMeSi) produced sedimentary aerosol particles under UV light irradiation with a medi- um pressure mercury lamp at 313 nm and also with the third and fourth harmonics of a Nd:YAG laser. From the analysis of FT-IR band intensity change of the gaseous molecules, it was shown that photochemical reactions of Co(CO)3NO were accelerated by the pres- ence of ATMeSi molecules. Chemical structure of the sedimentary particles was analyzed by FT-IR and EDX-SEM. The results showed that the sedimentary particles consisted mainly of Co compounds, and a small amount of ATMeSi molecules played an essential role to form spherical particles. Linearly aggregated fine particles (particle-wires) were formed by modulating the convectional flow of the gaseous mixture.

BiCl3‐Catalyzed Propargylic Substitution Reaction of Propargylic Alcohols with C‐, O‐, S‐ and N‐Centered Nucleophiles.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

A General and Efficient FeCl3-Catalyzed Nucleophilic Substitution of Propargylic Alcohols

A general and efficient FeCl3-catalyzed substitution reaction of propargylic alcohols with carbon- and heteroatom-centered nucleophiles such as allyl trimethylsilane, alcohols, aromatic compounds, thiols, and amides, leading to the construction of C-C, C-O, C-S and C-N bonds, has been developed.

Nonchelated Alkene and Alkyne Complexes of d0 Zirconocene Pentafluorophenyl Cations

This paper describes the generation and properties of nonchelated d(0) zirconocene-aryl-alkene and alkyne adducts that are stabilized by the presence of beta-SiMe(3) substituents on the substrates and the weak nucleophilicity of the -C(6)F(5) ligand. The cationic complexes [(C(5)H(4)R)(2)Zr(C(6)F(5))][B(C(6)F(5))(4)] (4a: R = H, 4b: R = Me) were generated by methide abstraction from (C(5)H(4)R)(2)Zr(C(6)F(5))Me by Ph(3)C(+). NMR studies show that 4a,b contain an o-CF...Zr dative interaction and probably coordinate a PhCl molecule in PhCl solution. Addition of allyltrimethylsilane (ATMS) to 4a,b in C(6)D(5)Cl solution at low temperature produces an equilibrium mixture of (C(5)H(4)R)(2)Zr(C(6)F(5))(H(2)C=CHCH(2)SiMe(3))(+) (7a,b), 4a,b, and free ATMS. Similarly, addition of propargyltrimethylsilane (PTMS) to 4a produces an equilibrium mixture of Cp(2)Zr(C(6)F(5))(HCCCH(2)SiMe(3))(+) (8a), 4a, and free PTMS. The NMR data for 7a,b,and 8a are consistent with highly unsymmetrical substrate coordination and substantial polarization of the substrate multiple bond with significant positive charge buildup at C(int) and negative charge buildup at C(term). PTMS binds to 4a more strongly than ATMS does. The ATMS adducts undergo nondissociative alkene face exchange ("alkene flipping"), i.e., exchange of the (C(5)H(4)R)(2)Zr(C(6)F(5))(+) unit between the two alkene enantiofaces without decomplexation of the alkene, on the NMR time scale.

BiCl3-Catalyzed propargylic substitution reaction of propargylic alcohols with C-, O-, S- and N-centered nucleophiles

A general and efficient BiCl3-catalyzed substitution reaction of propargylic alcohols with carbon and heteroatom-centered nucleophiles such as allyl trimethylsilane, alcohols, aromatic compounds, thiols and amides, leading to the construction of C-C, C-O, C-S and C-N bonds, has been developed.

Solvent‐Dependent Chemoselectivities in Ce(IV)‐Mediated Oxidative Coupling Reactions.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Solvent-dependent chemoselectivities in Ce(IV)-mediated oxidative coupling reactions.

The oxidative coupling of 1,3-diketones, beta-keto esters, and beta-keto silyl enol ethers with allyl trimethylsilane in the presence of CTAN was investigated. In the case of acyclic diketones and esters, different chemoselectivities were observed in CH(3)CN and CH(2)Cl(2) leading to good yields of allylation and dihydrofuran products, respectively. [reaction: see text]

Facile enantioselective synthesis of a key homoallylic alcohol building block for polyketide synthesis: TiF4–BINOL catalyzed allylsilylation with allyl trimethylsilane

The titanium fluoride–BINOL catalyzed asymmetric allylsilylation of α,α-disubstituted aldehydes provides facile access to highly functionalized, chiral building blocks, which following simple recrystallization affords a key versatile starting material for polyketide synthesis in 96% ee.

Reactivity of acyclic (pentadienyl)iron(1+) cations with weak carbon nucleophiles

The reaction of acyclic tricarbonyl(pentadienyl)iron(1+) cations with allyl trimethylsilane or with excess furan leads to ( E, E-diene)iron complexes. Attack of these weak nucleophiles on the transoid form of the pentadienyl cation is presumably faster than attack on the more stable cisoid form.