5-benzoyl-7-halo-1,2-dihydro-3H-pyrrolo[1,2-a]-pyrrole-1-carboxylic acids, represented by the formula ##STR1## and the pharmaceutically acceptable non-toxic esters and salts thereof, wherein:R is hydrogen or lower alkyl;X is hydrogen, lower alkyl, lower alkoxyl, lower alkoxycarbonyl, carboxyl, lower alkylcarbonyl, sulfonic acid, sulfonic acid alkyl ester, fluoro, chloro, or bromo; and Y is chloro or bromo, which are novel, and 5-benzoyl-1,2-dihydro-3H-pyrrolo[1,2-a]pyrrole-1-carboxylic acids which are represented by the formula ##STR2## wherein X and R are as above defined except that X cannot be chloro or bromo, are prepared by decarboxylation of the corresponding 1,1 dicarboxylates. Intermediates in said preparation are also disclosed.