137204-62-7Relevant academic research and scientific papers
Br?nsted acid-promoted cyclizations of siloxy alkynes with unactivated arenes, alkenes, and alkynes
Zhang, Liming,Sun, Jianwei,Kozmin, Sergey A.
, p. 11371 - 11380 (2007/10/03)
In this article, we describe the development of a general concept for the development of new carbon-carbon bond-forming processes, which is based on Br?nsted acid-mediated activation of a siloxy alkyne, followed by efficient interception of the resulting highly reactive ketenium ion by unactivated arenes, alkenes or alkynes. We found that trifluoromethane sulfonimide (HNTf2) proved to be a superior promoter of these reactions compared to a range of other Br?nsted acids. This finding could be attributed to a high acidity of HNTf2 in aprotic organic solvents combined with a low nucleophilicity of the NTf2- anion. Depending on the nature of the nucleophile, the carbocyclizations proceeded either via 6-endo-dig or 5-endo-dig manifolds. In the case of 1-siloxy-1,5-diynes, the cyclizations occurred with a concomitant halide abstraction or arylation.
Bronsted acid-promoted cyclizations of siloxyalkynes with arenes and alkenes
Zhang, Liming,Kozmin, Sergey A.
, p. 10204 - 10205 (2007/10/03)
We have described the first Bronsted acid-mediated cyclizations of siloxyalkynes with simple arenes and alkenes to afford substituted tetralone and cyclohexenone derivatives. The most notable aspect of the carbocyclizations involving siloxyalkynes is the ability to employ a range of substrates that are not restricted to those containing electron-rich arenes and alkenes. The key mechanistic feature of the reaction is the generation of a highly reactive ketenium ion upon protonation of siloxyalkyne. We believe that the low nucleophilicty of the counteranion is crucial for enabling the formation and effective interception of this highly reactive intermediate. Copyright
Aldol Reaction and Robinson-Type Annelation Catalyzed by Lanthanoid Triisopropoxides
Okano, Tamon,Satou, Yoshikazu,Tamura, Motoshi,Kiji, Jitsuo
, p. 1879 - 1886 (2007/10/03)
Lanthanoid triisopropoxides are active catalysts for aldol reactions.Aldehydes give the corresponding β-hydroxyaldehydes at low temperatures in good yields, whereas ketones are less reactive, but form condensation products at high temperatures.Exceptionally, γ- or δ-diketones easily undergo condensation to give five- and six-membered unsaturated ketones in high yields.The lanthanoid propoxides, catalyzing the Michael addition of ketones to α,β-unsaturated ketones, which give δ-diketones, are also good catalysts for the Robinson-type annelation.In these reactions, the catalytic activity of the lanthanum propoxide is higher than those of the heavy lanthanoid propoxides, and is almost comparable to that of sodium isopropoxide.Since aluminum triisopropoxide shows poor activity, the lanthanoid propoxides are considerably basic for trivalent metal alkoxides.
