a lower alkyl group such as a methyl group ethyl group isopropyl group butyl group etc a carboxyl lower alkyl group such as a carboxymethyl group carboxyethyl group carboxybutyl group etc a di lower alkylamino lower alkyl group such as a dimethylaminomethyl group dimethylaminoethyl group diethylaminomethyl group diethylaminoethyl group etc or an amino group sulfuric acid used in this invention may be concentrated sulfuric acid or fuming sulfuric acid according to the practice of this invention the compound of formula ii is caused to react with an equimolar or excessive molar amount of the compound of formula iii in the presence of sulfuric acid at room temperature or under heating the amount of sulfuric acid used is usually more than 2 mole times preferably more than 5 mole times the amount of the compound of formula ii in addition at the reaction sulfuric acid itself used acts as an inorganic solvent but if necessary polyphosphoric acid etc may be further used as an inorganic solvent the reaction is usually finished within several minutes to several hours the desired product of formula i formed can be isolated from the reaction mixture by dispersing the reaction mixture in ice water and adjusting the ph of the solution to deposit the desired product the product.