Silyl Transfer Research Articles

Silylene Transfer to Allylic Sulfides: Formation of Substituted Silacyclobutanes

Silylene transfer to allylic sulfides results in a formal 1,2-sulfide migration. The rearrangement yields substituted silacyclobutanes, not the expected silacyclopropanes. The silacyclobutanes were elaborated by insertions of carbonyl compounds selectively into one carbon-silicon bond. A mechanism for the 1,2-sulfide migration is proposed involving an episulfonium ion intermediate.

A Theoretical Insight into the Mechanism of the Silver‐Catalysed Transsiliranation Reaction

AbstractDFT calculations on a silver‐catalysed transsiliranation reaction (silylene transfer from a silirane to an alkene) have shown the key role of a silylenesilver ion in the catalyticcycle. Although the corresponding triflate‐bound species has previously been detected by NMR and IR spectroscopy, no significant silylene‐transfer activity is predicted for such a nonionised structure. Several experimental results can be explained by this new reaction mechanism.

ChemInform Abstract: Silylene Transfer to α‐Keto Esters and Application to the Synthesis of γ‐Lactones.

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 of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Palladium-Catalyzed Silylene-1,3-Diene [4 + 1] Cycloaddition with Use of (Aminosilyl)boronic Esters as Synthetic Equivalents of Silylene

Silylboronic esters bearing a dialkylamino group on the silicon atoms reacted with 1,3-dienes in the presence of a palladium catalyst to give silacyclopent-3-enes (i.e., 2,5-dihydrosiloles) in high yields via efficient silylene transfer from the silylboronic ester to the 1,3-dienes. The [4 + 1] cycloaddition was applicable to the parent 1,3-butadiene and various mono-, di-, and trisubstituted 1,3-dienes having silyloxy, cyano, and ester groups. Stereospecific ring formation took place in the reaction with either stereoisomer of 5,7-dodecadiene: the (E,E)-diene gave the cis product, whereas selective formation of the trans product was observed in the reaction of the isomeric (E,Z)-diene. The [4 + 1] cycloaddition followed by dehydrogenation with DDQ or chloranil afforded 2,4- and 2,5-diarylsiloles.

Silylene-Mediated Ring Contraction of Homoallylic Ethers To Form Allylic Silanes

(-)-Isopulegol derivatives undergo a ring contraction under silylene-mediated conditions to provide cyclopentane products. Silylene transfer to other homoallylic ethers did not provide the ring contraction products. Allylic silane products were elaborated to determine the stereochemical course of the ring contraction reaction. A mechanism for the transformation is proposed.

Silylene transfer to α-keto esters and application to the synthesis of γ-lactones

Disubstituted α-hydroxy acids have been synthesized by metal-catalyzed silylene transfer to α-keto esters. A range of substituents are tolerated in the transformation with the exception of branched groups at the vinylic position. The α-hydroxy acid products can be converted into γ-lactones using a variety of lactonization conditions.

Alkylidenesilacyclopropanes Derived from Allenes: Applications to the Selective Synthesis of Triols and Homoallylic Alcohols

Several alkylidenesilacyclopropanes were prepared by silver-mediated silylene transfer to allenes. Oxasilacyclopentanes derived from allenes were prepared with high regio- and diastereoselectivity by a two-step, one-flask silacyclopropanation/carbonyl insertion reaction. Triols and homoallylic alcohols were formed diastereoselectively by functionalizing the oxasilacyclopentanes. An optically active allene (>98% ee) was utilized to synthesize an enantiopure homoallylic alcohol in 96% ee.

Intermolecular Silacarbonyl Ylide Cycloadditions: A Direct Pathway to Oxasilacyclopentenes

Silacarbonyl ylides, generated by metal-catalyzed silylene transfer to carbonyls, participate in formal intermolecular 1,3-dipolar cycloaddition reactions with carbonyl compounds and alkynes to form dioxasilacyclopentane acetals and oxasilacyclopentenes in an efficient, one-step process.

ChemInform Abstract: Catalytic Asymmetric C—Si Bond Formation to Acyclic α,β‐Unsaturated Acceptors by Rh(I)‐Catalyzed Conjugate Silyl Transfer Using a Si—B Linkage.

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 of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Catalytic Asymmetric CSi Bond Formation to Acyclic α,β‐Unsaturated Acceptors by RhI‐Catalyzed Conjugate Silyl Transfer Using a SiB Linkage

Catalytic Asymmetric CSi Bond Formation to Acyclic α,β‐Unsaturated Acceptors by Rh^I‐Catalyzed Conjugate Silyl Transfer Using a SiB Linkage

ChemInform Abstract: Synthesis of Tertiary α‐Hydroxy Acids by Silylene Transfer to α‐Keto Esters.

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 of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

N-Heterocyclic Carbene-Catalyzed Silyl Enol Ether Formation

N-Heterocyclic carbenes (NHCs) were found to catalyze the silyl transfer from trialkylsilyl ketene acetals to ketones. In the presence of a catalytic amount of NHC 3 (IAd, 0.1 to 5 mol %), a series of enolizable ketones as well as cyclohexanecarboxaldehyde were efficiently converted into the corresponding silyl enol ethers at 23 degrees C in THF.

シリレンの環化付加反応の有機合成化学的利用

In this short review, a new methodology of preparation of the silacyclic compounds using silylene and their application for organic synthesis are described. Silylene transfer from silacyclopropane to alkene, alkyne, imine, and α, β-unsaturated carbonyl compounds was catalyzed by silver salt to give the corresponding [1+2] or [1+4] cycloadducts in good yields. Combination of the cycloaddition, Ireland-Claisen rearrangement, and oxidative cleavage of silicon-carbon bond provided the regio-and stereoselective synthesis of polyol and α-hydroxyacid in a mild condition.

Synthesis of Tertiary α-Hydroxy Acids by Silylene Transfer to α-Keto Esters

Alpha-keto esters can be converted into alpha-hydroxy acids in a single flask involving metal-catalyzed silylene transfer, 6pi-electrocyclization, Ireland-Claisen rearrangement, and hydrolysis. This reaction sequence is stereoselective and tolerates alkyl- and aryl-substituted alpha-keto ester substrates as well as an alpha-imino ester.

Enantioselective Metallophosphite-Catalyzed C-Acylation of Nitrones

Metallophosphites derived from tartaric acid catalyze the enantioselective addition of acyl silanes to nitrones. The product α-N-silyloxyamino ketones are obtained in moderate to good yields (36−94%) with excellent enantioselectivity (er ≥ 95:5). The nitrone oxygen is essential in facilitating the silyl transfer that is required for catalyst turnover. This represents, to the best of our knowledge, the first example of C-acylation of nitrones and the most highly enantioselective catalytic addition of an acyl anion equivalent to an azomethine electrophile. The N−O bond of the product may be reductively cleaved under mild conditions to provide N-aryl α-amino ketones with negligible loss of enantiopurity.

Iridium-Catalyzed Reduction of Alkyl Halides by Triethylsilane

A highly active cationic Ir(III) hydride complex catalyzes the reduction of primary, secondary, and tertiary chlorides, bromides, and iodides as well as certain fluorides by Et3SiH. The catalytic cycle appears to operate by a unique process in which an electrophilic iridium silane complex acts as a silylating reagent to produce a silyl-substituted halonium ion which is then readily reduced by the nucleophilic dihydride formed following silyl transfer.

Metal-Catalyzed Silylene Transfer to Imines: Synthesis and Reactivity of Silaaziridines

Metal-catalyzed silylene transfer to imines provides an efficient synthesis of silaaziridines. These strained cyclic silanes undergo selective bond-forming reactions, permitting the synthesis of nitrogen-containing compounds after protodesilylation of the resulting vinyl silane.

Investigations on a Novel Silyl Transfer Reaction in Heterodimetallic Chemistry

Heterodinuclear silyl complexes of the type [(OC)3(R3Si)[Fe(mu-PPh2)Pt](CO)(PPh3)], which contain a [Fe(mu-P)Pt] triangular core, were previously reported to undergo an unprecedented dyotropic-type rearrangement involving migration of the silyl group from iron to platinum with concomitant 1,2 migration of CO from Pt to Fe. In the resulting complexes of formula [(OC)4[Fe(mu-PPh2)Pt](SiR3)(PPh3)], the Si atom occupies a cis position at the planar Pt center with respect to the phosphido bridge. DFT calculations were employed to elucidate the mechanism of this intramolecular silyl migration reaction. When the Fe-Pt precursor complex is [(OC)3(R3Si)[Fe(mu-PPh2)Pt](PPh3)2], the reaction sequence involves (i) the substitution of PPh3 by CO at Pt, (ii) the concerted migration of CO and SiR3, and (iii) the cis-trans isomerization at Pt. The calculations support the exergonic character of the overall process. An explanation for the experimental observation of only one product isomer being formed is possible via frontier molecular orbital analysis. Consistent with the experimental findings, the transition states of the migration (a species with a triply bridged intermetallic bond) and isomerization steps were found to be energetically within reach at room temperature. Additional support for the suggested mechanism also comes from the fact that relative silyl migration activities could be rationalized by the means of quantum chemistry.

Rhodium‐Catalyzed Enantioselective Conjugate Silyl Transfer: 1,4‐Addition of Silyl Boronic Esters to Cyclic Enones and Lactones.

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.

Copper‐Free and Copper‐Promoted Conjugate Addition Reactions of Bis(triorganosilyl) Zincs and Tris(triorganosilyl) Zincates.

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.