Oxalyl chloride combines with 1,3-bis(4-methylphenyl) propane-1,3-dione to afford novel titled compound furan-2,3-dione 1, whose synthesis, X-ray structure analysis and some reactions are reported. Thermolysis is supposed to occur by the ring opening of the compound 1 followed by the intermediate diacylketene dimerization resulting in the pyran-4-one 2. The reactions of 1 with some aromatic amines and diamines led to the formation of the pyrrole-2,3-diones 3, 4 and the quinoxalin-2-one derivatives 5, respectively. Most of them were compared with their previous analogs. The structures of all products were confirmed by IR, H-1- and C-13-NMR spectroscopic measurements, in the case of 1 also by an X-ray study. 1 crystallizes in the monoclinic space group C2/c with eight molecules 1 per cell. The reaction pathways leading to the compounds 1, 2 and 4 were briefly discussed.