METHOD OF PRODUCING DIOXAZINE

摘要

PROBLEM TO BE SOLVED: To provide a method of producing an dioxazine that gives reduced amounts of byproducts. SOLUTION: A dianilide represented by general formula (4) [wherein Ar and Ar' are each an aromatic group to be described in detail in general formula (1)] is cyclized in fuming sulfuric acid to monooxazine represented by general formula (5) [wherein Ar and Ar' have the same meanings as in the formula (4)]. Subsequently, the monooxazine is cyclized in persulfate salt to produce the objective dioxazine represented by general formula (1) [wherein Ar and Ar' represent each a benzene ring bearing one amino group and two sulfonate groups].