Synthesis and Reactions of 3‐Methylthiazolo[3,2‐a]Benzimidazole‐2‐Carboxylic Acid Hydrazide: Synthesis of Some New Pyrazole, 1,3‐Thiazoline, 1,2,4‐Triazole and 1,2,4‐Triazolo[3,4‐b]‐1,3,4‐Thiadiazine Derivatives Pendant to Thiazolo[3,2‐a]Benzimidazole Moiety |
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Authors: | Hatem A Abdel‐Aziz Nehal A Hamdy Ahmad M Farag Issa M I Fakhr |
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Institution: | 1. Applied Organic Chemistry Department, National Research Center, Dokki, Cairo 12622, Egypt;2. Department of Chemistry, Faculty of Science, Cairo University, Giza 12613, Egypt |
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Abstract: | The reaction of 3‐methylthiazolo3,2‐a]benzimidazole‐2‐carboxylic acid ethyl ester (1) with hydrazine hydrate gives the hydrazide 2 which reacts with CS2/KOH to afford the potassium salt 3. Treatment of 3 with l‐aryl‐2‐bromoethanones 4a,b afforded the 1,3‐thiazoline derivatives 6a,b, respectively, while the reaction of 3 with hydrazine hydrate afforded 1,2,4‐triazole‐3‐thione derivative 9. The reaction of 9 with l‐aryl‐2‐bromoethanones 4a,b and with hydrazonyl chlorides 11a,b gave the 1,2,4‐triazolo3,4‐b]‐1,3,4‐thiadiazine derivatives 10a,b and 12a,b, respectively. Treatment of hydrazide 2 with phenyl isothiocyanate in refluxing benzene gave the thiosemicarbazide derivative 16. The latter reaction gave 1,3,4‐oxadiazole derivative 17 when benzene was replaced by DMF. Cyclization of the thiosemicarbazide derivative 16 with NaOH resulted in the formation of the 1,2,4‐triazole‐3‐thione derivative 18. |
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Keywords: | Thiazolo[3 2‐a]benzimidazole Pyrazoles 1 3 4‐Oxadiazoles 1 3‐Thiazolidines 1 2 4‐Triazoles 1 2 4‐Triazolo[3 4‐b]‐1 3 4‐thiadiazines Hydrazonyl chlorides |
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