| 摘要 |
The present invention provides a method for producing a compound represented by formula (A), the method comprising the steps of: (a) mixing a compound represented by formula (B) with p-toluenesulfonic acid or p-toluenesulfonic acid monohydrate at less than 1 molar equivalent with respect to the compound represented by formula (B) in a solvent under heating; (b) adding additional p-toluenesulfonic acid or p-toluenesulfonic acid monohydrate to the mixed solution under cooling, wherein the additional p-toluenesulfonic acid or p-toluenesulfonic acid monohydrate is added in such an amount that the total molar equivalent thereof with the p-toluenesulfonic acid or p-toluenesulfonic acid monohydrate of step (a) is 1 molar equivalent or more with respect to the compound represented by formula (B) of step (a); and (c) subsequently allowing the mixed solution to crystallize to obtain the compound represented by formula (A). |
