Enantioselective Scandium-Catalyzed Vinylsilane Additions: A New Approach to the Synthesis of Enantiopure β,γ-Unsaturated α-Hydroxy Acid Derivatives
作者:David A. Evans、Yimon Aye
DOI:10.1021/ja063878k
日期:2006.8.1
The development of the Lewis acid-catalyzed alkenylation using trimethylvinylsilanes is described. Both aliphatic and aromatic vinylsilanes were effective nucleophiles at room temperature affording chiral allylic alcohol products in excellent enantioselectivities (97 → 99% ee) and in moderate to good yields (45−99%). Complete retention of vinysilane geometry was observed where applicable.
Arenediazonium tetrafluoroborates (ArN2BF4 where ArPh, 4-MeC6H4, 4-BrC6H4, 4-IC6H4 and 4-NO2C6H4) reacted easily with CH2CHSiMe3 at 25 δC to give ArCHCH2, (E-ArCHCHSiMe3 and Ar(Me3Si)CCH2 in excellent yields under palladium(O) catalysis. (E)-ArCHCHSiMe3 compounds were obtained predominantly and isolated in good yields by using an excess of CH2CHSiMe3 over ArN2BF4. Protodesilylation of the reaction
Direct coupling of alcohols with alkenylsilanes catalyzed by indium trichloride or bismuth tribromide
作者:Yoshihiro Nishimoto、Masayuki Kajioka、Takahiro Saito、Makoto Yasuda、Akio Baba
DOI:10.1039/b816072d
日期:——
Indium halides or bismuth halides catalyzed the coupling of various alcohols with alkenylsilanes to give the corresponding alkenes stereospecifically without any other activators.
Treatment of triphenylbismuth difluoride with alkenyltrimethylsilanes 1 or trimethylsilyl cyanide–alkenyltrialkylstannanes 3 in the presence of boron trifluoride–diethyl ether gave the corresponding alkenyltriphenylbismuthonium tetrafluoroborates 2 in moderate to good yields. An X-ray crystallographic analysis of the salt 2e confirmed the distorted tetrahedral geometry of the central bismuth atom. When treated with a sulfinate 5 or the thiolate 11, the salts 2 readily transferered both the vinyl and phenyl moieties to these nucleophiles to afford the sulfones 7–10 or the sulfides 12, 13, respectively. In the presence of a palladium catalyst, the salt 2e underwent the Heck-type reaction with ethyl acrylate 17 to afford the dienoate 18 and cinnamate 19 in moderate yields. Action of KOBut on the salt 2b yielded p-tolylacetylene 22, while a similar reaction with the salt 2e in the presence of the styrenes 23 gave the cyclopropanes 24. A Hammett study of the latter reaction has suggested a possible involvement of an alkylidenecarbene as the intermediate in these base-promoted reactions.
作者:Mendoza-Espinosa, Daniel、Rendón-Nava, David、Vásquez-Pérez, Jose M.、Sandoval-Chávez, Cesar I.、Alvarez-Hernández, Alejandro
DOI:10.1021/acs.organomet.0c00517
日期:——
of complexes 4a–d featuring a [Rh(CO)2I] fragment used for the detemination of the donor properties of the new triazolylidene ligands. All complexes have been fully characterized by means of 1H and 13C NMR spectroscopy, melting point, elemental analysis, and in the case of complex 3a, by X-ray crystallography. Comparison of the catalytic activity of the new rhodium complexes in C–C and C–Si bond forming