32346-08-0Relevant academic research and scientific papers
Coupling Reaction of Enol Derivatives with Silyl Ketene Acetals Catalyzed by Gallium Trihalides
Nishimoto, Yoshihiro,Kita, Yuji,Ueda, Hiroki,Imaoka, Hiroto,Chiba, Kouji,Yasuda, Makoto,Baba, Akio
supporting information, p. 11837 - 11845 (2016/08/05)
A cross-coupling reaction between enol derivatives and silyl ketene acetals catalyzed by GaBr3took place to give the corresponding α-alkenyl esters. GaBr3showed the most effective catalytic ability, whereas other metal salts such as BF3?OEt2, AlCl3, PdCl2, and lanthanide triflates were not effective. Various types of enol ethers and vinyl carboxylates as enol derivatives are amenable to this coupling. The scope of the reaction with silyl ketene acetals was also broad. We successfully observed an alkylgallium intermediate by using NMR spectroscopy, suggesting a mechanism involving anti-carbogallation among GaBr3, an enol derivative, and a silyl ketene acetal, followed by syn-β-alkoxy elimination from the alkylgallium. Based on kinetic studies, the turnover-limiting step of the reaction using a vinyl ether and a vinyl carboxylate involved syn-β-alkoxy elimination and anti-carbogallation, respectively. Therefore, the leaving group had a significant effect on the progress of the reaction. Theoretical calculations analysis suggest that the moderate Lewis acidity of gallium would contribute to a flexible conformational change of the alkylgallium intermediate and to the cleavage of the carbon?oxygen bond in the β-alkoxy elimination process, which is the turnover-limiting step in the reaction between a vinyl ether and a silyl ketene acetal.
Gallium tribromide catalyzed coupling reaction of alkenyl ethers with ketene silyl acetals
Nishimoto, Yoshihiro,Ueda, Hiroki,Yasuda, Makoto,Baba, Akio
supporting information; experimental part, p. 8073 - 8076 (2012/08/29)
A 'Ga'llant couple: The α-alkenylation of esters was accomplished by GaBr3-catalyzed coupling between alkenyl ethers and ketene silyl acetals. In this reaction system, various alkenyl ethers, including those with vinyl and substituted alkenyl groups, were applicable, and the scope of applicable ketene silyl acetals was sufficiently broad. The mechanism is also discussed. Copyright
Carbogallation of alkynes using gallium tribromide and silyl ketene acetals and synthetic application to cross-coupling with aryl iodides
Nishimoto, Yoshihiro,Ueda, Hiroki,Yasuda, Makoto,Baba, Akio
supporting information; experimental part, p. 11135 - 11138 (2011/10/31)
Try substituted alkynes with GaBr3: The regio- and stereoselective carbogallation of alkynes has been achieved by a simple treatment of GaBr3, alkynes, and ketene silyl acetals. The produced alkenylgallium compounds can be used for the synthesis of selective trisubstituted alkenes through successive cross-coupling with aryliodides (see scheme). The usability of the carbogallation was presented by the total synthesis of meroterpenoid nodosol, which was extracted from the seagrass Cymodocea nodosa. Copyright
Indium tribromide catalyzed cross-Claisen condensation between carboxylic acids and ketene silyl acetals using alkoxyhydrosilanes
Nishimoto, Yoshihiro,Okita, Aya,Yasuda, Makoto,Baba, Akio
supporting information; experimental part, p. 8623 - 8625 (2011/11/06)
Acylations achieved: The title reaction between carboxylic acids and ketene silyl acetals has been accomplished (see scheme). The additive, (MeO) 3SiH, is believed to play an important role in the promotion of the condensation reaction. This reaction system was compatible with a diverse range of functional groups, including alkenes, alkynes, chlorides, alcohols, esters, and nitro groups. Copyright
The Synthesis of O-Silyl Ketene Acetals from α-Haloesters
Schulz, William J.,Speier, John L.
, p. 163 - 166 (2007/10/02)
α-Haloesters of the general structure R1R2CXCO2R3 1 have been shown to react with sodium in the presence of a halosilane 2 to yield the corresponding O-silyl ketene acetals 3 (SKAs) according to equation 4.The factor that most influences the yields in these reactions is the concentration of halosilane; if there is a deficiency of halosilane, then acyloin condensation products will detract from the yield of SKAs.The reaction is quite general, and often gives yields in excess of 90percent of the desired SKAs.
