Preferential Geminal Bis-silylation of 3,4-Benzothiophane Is Caused by the Dominance of Electron Withdrawal by R3Si over Steric Shielding Effects
نویسندگان
چکیده
Benzylic C-H lithiation of 3,4-benzothiophane and subsequent treatment with triphenyl- or trimethylchlorosilane under a variety of conditions leads to α,α- rather than α,α'-bis-silylation products as a consequence of anion stabilization by R3Si and very fast deprotonation of the intermediate monosilylated product, even with a sterically bulky base such as lithium diisopropylamide.
منابع مشابه
An alternative mechanistic paradigm for the β-Z hydrosilylation of terminal alkynes: the role of acetone as a silane shuttle.
The β-Z selectivity in the hydrosilylation of terminal alkynes has been hitherto explained by introduction of isomerisation steps in classical mechanisms. DFT calculations and experimental observations on the system [M(I)2{κ-C,C,O,O-(bis-NHC)}]BF4 (M=Ir (3a), Rh (3b); bis-NHC=methylenebis(N-2-methoxyethyl)imidazole-2-ylidene) support a new mechanism, alternative to classical postulations, based...
متن کامل[1,5]-Brook rearrangement: an overlooked but valuable silyl migration to synthesize configurationally defined vinylsilane. The unique steric and electronic effects of geminal bis(silane).
An unusual [1,5]-Brook rearrangement of the lithium alkoxide of geminal bis(silyl) homoallylic alcohol is described. The unique steric and electronic effects of geminal bis(silane) were found to be crucial for promoting this long-range silyl migration, as well as for facilitating the subsequent γ/Z-selective addition of silyl allyllithium with carbonyl compounds to synthesize diverse configurat...
متن کاملA STUDY OF THE SILYLATION REACTION OF CYANOEPOXIDES WITH TRIMETHYLCHLOROSILANE IN THE PRESENCE OF MAGNESIUM
In the presence of magnesium and hexamethylphosphorictriamide, HMPT, trimethylchlorosilane, TMS-C1, reacts with cyanoepoxides to give related compounds. Ring cleavage at ? - position of cyanoepoxide, 1, followed by the addition of two trimethylsilyl groups leads to 2 then substitution of OSiMei by trimethylsilyl or H takes place to give ?, ? - bis (trimethylsilyl) nitrile or ? - trimethyls...
متن کاملSilylation of Alcohols and Phenols Using HMDS Catalyzed by SiO2-Cl in Solution and Solvent-Free Conditions
Trimethylsilylation of a variety of alcohols and phenols, in the presence of silica chloride, using hexamethyldisilazane (HMDS) in solution and under solvent-free conditions is reported. Trimethylsilyl ethers were formed in excellent yields both for aliphatic alcohols and phenols without having an electron-withdrawing group. In addition, SiO2-Cl can be recovered and reused after drying.
متن کاملShielding simulations for safe use of curtain electron accelerator by MCNP4C
In an electron curtain accelerator, when the electron beam passes through the titanium exit window of the accelerator chamber, X-ray photons are produced as a negative by-product of retarding accelerated electrons. Controlling the produced X-ray photons to avoid their detrimental effects or in fact, proper shielding of the accelerator is an important issue that has to be considered in the use o...
متن کامل