Patent US2558862 - Manufacture of brominated phthalic anhydride ...

http://www.google.com/patents/US2558862

Electrophilic aromatic substitution. You need to generate a bromonium ion, say using NaBrO3 and HBr. There are other methods as well. Follow this with some chromatography and you should have bromophthalic anhydrides.

if you are working at microscale you could use as an alternative, NBS in methanol, remember that NBS is a good form to produce bromonium ion. Even the reaction of NaBrO3 / HBr , is a very good idea too !

In this web page:

http://www.google.co.in/patents/US4962206