An Efficient Synthesis of New Thiazole Based Heterocycles (original) (raw)

Synthesis of new aminopyrazole, pyrazolo[3,4-d]-1,2,3-triazine, 1,3,4thiadiazole, thiophene and 1,2-dihydropyridine derivatives containing thiazole template has been carried out by simple, efficient and good yielding routes starting from the versatile and readily accessible 2-cyano-N-(thiazol-2-yl)acetamide. Thiazoles and their derivatives have attracted continuing interest over the years because of their diverse biological activities. 1,2 They found application in drug development for the treatment of allergies, 3 hypertension, 4 inflammation, 5 schizophrenia, 6 bacterial 7 and HIV infections. 8 They are also used as hypnotics, 9 for the treatment of pain, 10 and as inhibitors of LFA-1/ICAM-1 mediated cell adhesion. 11 In addition, thiazole derivatives show strong FabI and FabK inhibitory effects with potent antibacterial activity. 12 In view of the above mentioned findings, and as a continuation of our interest in the synthesis of a variety of heterocyclic ring systems for biological evaluation, 13-28 we report in the present work the synthesis of some heterocycles containing thiazole template. During our search, we have found that 2-cyano-N-(thiazol-2-yl)acetamide (1) 29 is a versatile, readily accessible building block for synthesis of the target compounds. Treatment of the acetamide 1 with 2-oxo-N'-phenylpropanehydrazonoyl chloride (2) 30 in ethanolic sodium ethoxide, at room temperature, furnished a single product identified as the aminopyrazole derivative 4a. The IR spectrum of the reaction product exhibited absorption bands at 3443, 3331, 3191, 1692 and 1638 cm-1 due to amino, amide-NH and two carbonyl groups, respectively. Prompted by the foregoing results and to generalize this reaction, we have also studied the behaviour of the acetamide 1 towards the 2-oxo-2-(phenylamino)-N'-p-tolylacetohydrazonoyl chloride (5a), 31 under the same experimental