σ- versus π-Activation of Alkynyl Benzoates Using B(C6F5)3

Molecules

Alexander Bähr¹  Lewis C. Wilkins¹  Kevin Ollegott¹  Benson M. Kariuki¹  Rebecca L. Melen² 

[1] School of Chemistry, Main Building, Cardiff University, Cardiff CF10 3AT, Cymru/Wales, UK;

关键词: boron;    trispentafluorophenyl borane;    B(C₆F₅)₃;    Lewis acid;    alkyne;   

DOI  :  10.3390/molecules20034530

来源: mdpi

【 摘 要 】

We have prepared a range of alkynyl benzoates in high yields and have investigated their reactivities with the strong Lewis acid B(C₆F₅)₃. In such molecules both σ-activation of the carbonyl and π-activation of the alkyne are possible. In contrast to the reactivity of propargyl esters with B(C₆F₅)₃ which proceed via 1,2-addition of the ester and B(C₆F₅)₃ across the alkyne, the inclusion of an additional CH₂ spacer switches off the intramolecular cyclization and selective σ-activation of the carbonyl group is observed through adduct formation. This change in reactivity appears due to the instability of the species which would be formed through B(C₆F₅)₃ activation of the alkyne.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.