78133-20-7Relevant academic research and scientific papers
Enantioselective Silicon-Directed Nazarov Cyclization
Cao, Jin,Hu, Meng-Yang,Liu, Si-Yuan,Zhang, Xin-Yu,Zhu, Shou-Fei,Zhou, Qi-Lin
, p. 6962 - 6968 (2021)
The Nazarov electrocyclization reaction is a convenient, widely used method for construction of cyclopentenones. In the past few decades, catalytic asymmetric versions of the reaction have been extensively studied, but the strategies used to control the position of the double bond limit the substituent pattern of the products and thus the synthetic applications of the reaction. Herein, we report highly enantioselective silicon-directed Nazarov reactions which were cooperatively catalyzed by a Lewis acid and a chiral Br?nsted acid. The chiral cyclopentenones we synthesized using this method generally cannot be obtained by means of other catalytic enantioselective reactions, including previously reported methods for enantioselective Nazarov cyclization. The silicon group in the dienone substrate stabilized the β-carbocation of the intermediate, thereby determining the position of the double bond in the product. Mechanistic studies suggested that the combination of Lewis and Br?nsted acids synergistically activated the dienone substrate and that the enantioselectivity of the reaction originated from a chiral Br?nsted acid promoted proton transfer reaction of the enol intermediate.
A facile stereoselective synthesis of (2E)-3-silylallylic alcohols by hydromagnesiation of 1-aryl-2-silylacetylenes
Cai, Mingzhong,Zhou, Zhou,Jiang, Jianwen
, p. 1400 - 1402 (2007/10/03)
Hydromagnesiation of 1-aryl-2-silylacetylenes 1 in diethyl ether gave (1E)-2-silylvinyl Grignard reagents 2, which reacted with aldehydes or ketones 3 to afford stereoselectively (2E)-3-silylallylic alcohols 4 in good to high yields. Wiley-VCH Verlag GmbH
Cp2TiCl2-CATALYZED GRIGNARD EXCHANGE REACTIONS WITH ACETYLENES. A CONVENIENT METHOD FOR PREPARATION OF E-ALKENYL GRIGNARD REAGENTS
Sato, Fumie,Ishikawa, Hiroaki,Sato, Masao
, p. 85 - 88 (2007/10/02)
Disubstituted acetylenes react with isobutylmagnesium halide in the presence of a catalytic amount of Cp2TiCl2 in ether to afford E-alkenyl Grignard reagents selectively and in almost quantitative yields.The regiochemistry of this hydromagnesation reaction is high for alkylarylacetylenes and silylacetylenes giving E-ArC(MgBr)=CHR from alkylarylacetylenes, E-ArC(MgBr)=CH(SiMe3) from arylsilylacetylenes, and E-CHR=C(MgBr)(SiMe3) from alkylsilylacetylenes, respectively.Thanks to the high reactivity of the Grignard reagent, the present reaction offers a novel, selective and operationally simple route for preparation of trisubstituted olefins.
