From simple phenols to potent chain-breaking antioxidants by transposition of benzo[1,4]oxathiines to benzo[b]thiophenes

Simple phenols, including food stock recycled derivatives, were used for the synthesis of 1,4-benzooxathiine intermediates, with limited or no antioxidant activity. Depending upon their substitution pattern, these compounds, through an acid promoted transposition, can be converted into o-hydroxydihydrobenzo[b]thiophenes or o-hydroxy-benzo[b]thiophenes as a new class of potent chain-breaking antioxidants, showing, in the reaction with alkyl peroxyl radicals, kinetic rate constants (kinh) comparable to that of α−tocopherol, the more potent natural lipophilic phenolic antioxidant.