Abstract:
A process for preparing substituted phthalic anhydrides, e.g. 4-methylphthalic anhydride, in which the Diels-Alder addition product of a conjugated diene, e.g. isoprene, and maleic anhydride is reacted with bromine in the presence of an acid acceptor. The acid acceptor can be present in catalytic amounts. Typical acid acceptors include dimethylformamide and pyridine.