To obtain the above compound important as an intermediate for producing chemicals in a high yield without producing by products by oxidizing specific phenols with an oxidizing agent in the presence of specific phenols.

(A) Phenols of formula I (X is H or hydroxyl; R1 to R4 are H or an alkyl, an alkoxy, an alkylsulfonyl, an arylaryloxy, etc., which may have a substituent group) are oxidized with (C) an oxidizing agent in the presence of (B) a metal porphyrin complex (the metal is a complex-forming metal, preferably either one of Fe, N, Cr and Mn) to provide the objective compound of formula H. Moreover, the component B is preferably either one of hematins, hemins, hemes, hemoglobins and methemoglobin and the component C is preferably hydrogen peroxide or a material capable of isolating the hydrogen peroxide.