Tetra-acetylethylene (I), prepared by oxidation with iodine of the dithallium(1) salt of tetra-acetylethane (11), reacts with hydrazine to give a mixture of 1,4,5,8-tetramethylpyridazino [4,5-d] pyridazine (IV) and 6-amino-1,4,5,7-tetramethylpyrrolo[3,4-d]pyridazine (V). Treatment of compound (I) with hydrochloric or hydrobromic acid yields furan derivatives, whose structures can be established by chemical and spectroscopic methods. Compound (I) gives a Diels-Alder adduct with 2,3-dimethylbutadiene.THIS work arose from attempts to synthesise 1,4,5,8tetramethylpyridazino[4,5-d]pyridazine (IV) . Pyridazines can be obtained by the reaction of hydrazine with 2,3-unsaturated 1,4-diketones; 2-4 we therefore needed to prepare t etra-acetylethylene (3,4-diacetylhex-3-ene-2,5-dione) (I).Attempts to prepare this compound from 3-bromoacetylacetone, in alkaline medium, failed. Oxidation, by iodine, of tetra-acetylethane (11), previously treated with sodium ethoxide (2 mol.), was equally unsuccessful. However, oxidation of the dithallium(1) salt of compound (11) afforded compound (I) as pale yellow needIes, m.p. 139-140'.The i.r. evidence strongly supports a centrosymmetric structure for this compound in the solid state: only two carbonyl bands (1690 and 1680 crn.-l) are observed in the double bond region. In solution a small distortion probably occurs since besides the bands at 1690 and 1703 cm.-l, the Raman modes at 1703 (C=O) and 1600 (C=C) cm.-l appear as weak bands at about the same frequencies.