title: A Straightforward Route to Potent Phenolic Chain-Breaking Antioxidants by Acid-Promoted Transposition of 1,4-Benzo[b]oxathiines to Dihydrobenzo[b]thiophenes.
abstract: The transformation of simple phenols with limited antioxidant activity into potent chain-breaking antioxidants was achieved by a three-step protocol, consisting of the conversion of phenols into 1,4-benzo[b]oxathiines followed by an unprecedented acid-promoted transposition to o-hydroxydihydrobenzo[b]thiophenes, or dihydrobenzo[de]thiochromenes, starting from phenols or naphthols, respectively. These derivatives, bearing a benzo-fused heterocycle with a sulfide sulfur ortho to the phenolic OH, have a rate constant of reaction with alkylperoxyl radicals (kinh ) comparable to that of α-tocopherol. A solid rationale for the transposition mechanism as well as for the structure-antioxidant activity relationship is presented.
authors.affiliation: Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3-13, 50019, Sesto Fiorentino, Firenze (Italy). caterina.viglianisi@unifi.it.
authors.forename: Caterina
authors.initials: C
authors.lastname: Viglianisi
authors.affiliation: Department of Chemistry "G. Ciamician", University of Bologna, Via S. Giacomo 11, 40126 Bologna (Italy).
authors.forename: Riccardo
authors.initials: R
authors.lastname: Amorati
authors.affiliation: Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3-13, 50019, Sesto Fiorentino, Firenze (Italy).
authors.forename: Leonardo
authors.initials: L
authors.lastname: Di Pietro
authors.affiliation: Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3-13, 50019, Sesto Fiorentino, Firenze (Italy). stefano.menichetti@unifi.it.
authors.forename: Stefano
authors.initials: S
authors.lastname: Menichetti
keywords: S heterocycles; antioxidants; electrophilic substitution; phenols; vitamins