Darzens reaction of 2‐bromo‐4,6‐dimethoxy‐3(2 H )‐benzofuranone with aromatic aldehydes to form flavonoids

The applicability of 2‐bromo‐4,6‐dimethoxy‐3(2 H )‐benzofuranone ( 1 ) to produce flavonoid‐derived epoxides in the course of the Darzens reaction with aldehydes was investigated. However, instead of the epoxides, flavonols 3 and, in certain cases, benzofuranyl‐substituted flavonols 4 were isolated. The generation of 3 is assumed due to a ring expansion of the initially formed epoxides. These flavonols can react with 1 to produce the unexpected 1:2 adducts 4 as minor products. The structure of the hexamethoxy derivative 4b (R 1 = H, R 2 = R 3 = OMe) was confirmed by X‐ray crystallographic analysis.