✍ Scribed by Kamal M. Dawood
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The pyridinium salts 2a,b reacted with dimethyl acetylenedicarboxylate (DMAD) to give the indolizine derivatives 6a,b. Pyridinium salts 2a,b also reacted with pyrazole‐5‐diazonium salt to afford the hydrazonoyl bromides 8a,b, which on treatment with aqueous ethanolic sodium carbonate furnished the 8a__H__‐1,2,4‐triazolo[4,3‐a]pyridine 10. When sulfonium bromide 11 was treated with nitrous acid and with pyrazole‐5‐diazonium salt, it afforded the new hydroximoyl and hydrazonoyl halides 12 and 17, respectively. Compound 12 reacted with 2‐methylthiobenzimidazole to furnish benzimidazo[1,2‐d]‐1,2,4‐oxadiazole derivative 14. Treatment of either 12 with 3‐phenyl‐5‐aminopyrazole or 17 with triethylamine resulted in the formation of the same product: pyrazolo[1,5‐c]‐1,2,4‐triazole derivative 16. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:432–436, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20037
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## Abstract magnified image __E__‐3‐(__N,N__‐Dimethylamino)‐1‐(3‐methylthiazolo[3,2‐__a__]benzimidazol‐2‐yl)prop‐2‐en‐1‐one (**2**) was synthesized by the reaction of 1‐(3‐methylthiazolo[3,2‐__a__]benzimidazol‐2‐yl)ethanone (**1**) with dimethylformamide‐dimethylacetal. The reaction of **2** with