Flavanoid Expoxides - XIII: Acid and Base Catalysed Reactions of 2'-Tostyloxychalcone epoxides. Mechanism of the Algar-Flynn-Oyamada Reaction

2'-Tosyloxychalcon.e epoxide (6a) on reaction with alkali gave flavonol (4a) while similar treatment of 6'-methoxy-2'-tosyloxychalcone·epoxide (6b), both at room temperature and. at the boiling point of the reaction medium, afforded 5-methoxyaurone (5b). The latter result indicates that an epoxide is not an intermediate in the production of flavanols from 2'-hydroxy-6'-methoxychalcone epoxides on treatment with alkaline hydrogen peroxide (AFO Reaction) at the higher temperature. Epoxide 6a on treatment with boron trifluoride etherate gave a mixture of flavanonol and flavonol while epoxide 6b gave.formyldesoxybenzoin (9) under similar conditions.