Preparation of halophthalic anhydrides

Abstract

A process for selectively substituting an aromatic nitro group of a nitrophthalic anhydride with a halo group which comprises contacting the nitroaromatic-containing compound with a phosphorus halide of formula: R.sub.n PX.sub.5-n wherein n is selected from 0, 1, 2 and 3; R is selected from the group consisting of C-6 to C-10 aryl and substituted aryl wherein the substituents are selected from the group consisting of: straight and branched chain alkyl, alkoxy, and haloalkyl; halogen, sulfonate and mixtures thereof; and X is a halogen. The process can take place in the presence of an arylphosphorusoxydihalide solvent or without using a solvent. The use of an arylphosphorustetrahalide and particularly phenylphosphorustetrachloride is preferred. The arylphosphorustetrahalide can be prepared in situ by contacting a solution of the corresponding arylphosphorusdihalide in an arylphosphorusoxydihalide solvent with a halogen. The process can further comprise the step of heating the reaction mixture to maintain a temperature of from about 25.degree. C. to about 175.degree. C. for from about 1 hour to about 24 hours.

Dependencies are inferred from the claim text.