1,2,5-Chalcogenadiazoles fused with electron-withdrawing heterocycles have been actively investigated for the preparation of organic photovoltaic materials. [1,2,5]Oxadiazolo[3,4-d]pyridazines are much less studied than other chalcogenadiazolopyridazines due to their low availability. In this communication, we report our study showing that 5,6-dihydro-[1,2,5]oxadiazolo[3,4-d]pyridazine-4,7-dione, a key precursor for the synthesis of 4,7-dihalo-[1,2,5]oxadiazolo[3,4-d]pyridazines, is formed via the cyclization of 1,2,5-oxadiazole-3,4-dicarbohydrazide in hydrochloric acid. The structure of the newly synthesized compound was established by means of elemental analysis; high-resolution mass spectrometry; 1H and 13C NMR; IR spectroscopy, and mass spectrometry.

New donor-acceptor-donor (D-A-D)-type structures are widely used to design effective organic light-emitting diodes (OLEDs). In this communication, 4,7-bis(1,2,3,4,4a,9a-hexahydro-9H-carbazol-9-yl)-[1,2,5]oxadiazolo[3,4-d]pyridazine was obtained in a 65% yield by the treatment of 4,7-dichloro[1,2,5]oxadiazolo[3,4-d]pyridazine 1-oxide with 2,3,4,4a,9,9a-hexahydro-1H-carbazole. The structure of the newly synthesized compounds was established by means of an elemental analysis, 1H, 13C NMR, IR and UV spectroscopy, and HRMS and LR mass-spectrometry.

Electron-withdrawing heterocyclic units are found in most organic optoelectronic materials. Benzo[1,2-d:4,5-d′]bis([1,2,3]thiadiazole) is an interesting new heterocyclic system, the chemical properties of which are much less studied than other fused thiadiazoles. Cyano derivatives of electron-accepting heterocycles are known as potential components of photoluminescent materials. In this communication, benzo[1,2-d:4,5-d′]bis([1,2,3]thiadiazole)-4-carbonitrile was successfully obtained via the cyanation of 4-bromobenzo[1,2-d:4,5-d′]bis([1,2,3]thiadiazole) with copper(I) cyanide in DMF. The structure of the newly synthesized compound was established by means of elemental analysis, high-resolution mass spectrometry, 1H and 13C NMR, and IR spectroscopy.