American Hoechst Corporation

James R Hazen

Richard L Castenson

Rex Y Tien

A novel method for the preparation of 4-bromo-1,8-naphthalic acid anhydride is disclosed. This method is carried out by the bromination, with alkali metal bromide or molecular bromine in the presence of a hypohalite, of a di-alkali metal salt of 1,8-naphthalic acid in aqueous solution at a pH of between 6.5 and 9.5 and at a temperature of between 0.degree. and 30.degree. C. to a di-alkali metal salt of 4-bromo-1,8-naphthalic acid and cyclizing to produce 4-bromo-1,8-naphthalic acid anhydride. This novel direct bromination method produces the desired product in good yields and high purity. 4-Bromo-1,8-naphthalic acid anhydride is a valuable intermediate for the preparation of dyestuffs, pigments and optical brighteners.

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Warwick, RI, United States of America

James R Hazen