title: Σ- versus π-activation of alkynyl benzoates using B(C₆F₅)₃.
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.
authors.affiliation: School of Chemistry, Main Building, Cardiff University, Cardiff CF10 3AT, Cymru/Wales, UK. alexander.baehr@rub.de.
authors.forename: Alexander
authors.initials: A
authors.lastname: Bähr
authors.affiliation: School of Chemistry, Main Building, Cardiff University, Cardiff CF10 3AT, Cymru/Wales, UK. WilkinsLC@cardiff.ac.uk.
authors.forename: Lewis C
authors.initials: LC
authors.lastname: Wilkins
authors.affiliation: School of Chemistry, Main Building, Cardiff University, Cardiff CF10 3AT, Cymru/Wales, UK. kevin.ollegott@rub.de.
authors.forename: Kevin
authors.initials: K
authors.lastname: Ollegott
authors.affiliation: School of Chemistry, Main Building, Cardiff University, Cardiff CF10 3AT, Cymru/Wales, UK. KariukiB@cardiff.ac.uk.
authors.forename: Benson M
authors.initials: BM
authors.lastname: Kariuki
authors.affiliation: School of Chemistry, Main Building, Cardiff University, Cardiff CF10 3AT, Cymru/Wales, UK. MelenR@cardiff.ac.uk.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Melen
mesh_terms: D000480:Alkynes / Q000138:chemical synthesis* / Q000737:chemistry; D001565:Benzoates / Q000138:chemical synthesis* / Q000737:chemistry; D058116:Lewis Acids; D008958:Models, Molecular; D015394:Molecular Structure; D014961:X-Ray Diffraction
chemical_list: D000480:Alkynes; D001565:Benzoates; D058116:Lewis Acids