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Updated: Apr 16, 2026

Efficient Synthesis of Polyfunctionalized Benzenes in Water via Persulfate-promoted Benzannulation of α,β-Unsaturated Compounds and Alkynes
Published on: December 16, 2019
Σ- versus π-activation of alkynyl benzoates using B(C₆F₅)₃
Alexander Bähr1, Lewis C Wilkins2, Kevin Ollegott3
1School of Chemistry, Main Building, Cardiff University, Cardiff CF10 3AT, Cymru/Wales, UK. alexander.baehr@rub.de.
Abstract:
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.
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