Process for the preparation of asymmetrically substituted maleic

Abstract

Compounds of the formula I ##STR1## in which R, R.sub.1 and R.sub.2 are as defined in patent claim 1, can be prepared by a novel process, for example by treating a salt of imidazo[1,2-a]pyridin-2(3H)-one with fumaric acid, maleic acid or maleic anhydride, in the presence of a base, and converting the product to a salt of 3-(1,2-dicarboxyethyl)-imidazo[1,2-a]pyridin-2(3H)-one, in the presence of a strong acid, reacting the latter salt with a compound CH.sub.2 =C(R.sub.1)(R.sub.2) and treating the intermediate obtained with glacial acetic acid and sodium acetate. The compounds (I) can be converted, in a manner known per se, to corresponding imides having functional groups suitable for polymerization reactions of polycondensation reactions. These imides can be used to prepare photocrosslinkable polymers. The anhydrides (I) can also be used, in some cases, to prepare pharmaceutically active benzofuranones and homosalicylic acids by reaction with salts of suitable amines.