Some 5-alkyl-2-amino-1,3,4-thiadiazoles have been synthesized by the MW-mediated solvent-free method. The reaction mixture is consisted of aliphatic acid, thiosemicarbazide and concentrated sulfuric acid (98%). Molar ratio of thiosemicarbazide and carboxylic acid was 1:2, reaction time was shortened (20 houres vs. 30 minutes). The structures of these aminothiadiazoles were confirmed by spectrospcopic methods (IR and 1 H-NMR). | Journal of Chemistry, Vol. 47 (4), P. 518 - 522, 2009 MICROWAVE-ASSISTED DIRECT SYNTHESIS OF SOME 5-ALKYL2-AMINO-1,3,4-THIADIAZOLES Received 10 December 2008 1* Nguyen Dinh Thanh , Pham Hong Lan2 and Nguyen Thi Minh Hai1 1 Faculty of Chemistry, Hanoi University of Science, VNU 2 Institute E17,Head Department VI, Ministry of Public Security Abstract Some 5-alkyl-2-amino-1,3,4-thiadiazoles have been synthesized by the MW-mediated solvent-free method. The reaction mixture is consisted of aliphatic acid, thiosemicarbazide and concentrated sulfuric acid (98%). Molar ratio of thiosemicarbazide and carboxylic acid was 1:2, reaction time was shortened (20 houres vs. 30 minutes). The structures of these aminothiadiazoles were confirmed by spectrospcopic methods (IR and 1H-NMR). I - Introduction The different classes of thiadiazole compounds have drawn attention of many organic chemists during recent years, since many of these compounds known to possess interesting biological properties such as antimicrobial [1], antituberculosis [2], antiinflammatory [3], anticonvulsant [4], antihypertensive [5], local anesthetic [6], anticancer [7] and hypoglycemic activities [8]. The 1,3,4-thiadiazole derivatives, hence, were synthesized with the aim of new antituberculosis drugs development. The most common procedure for synthesis of 5substituted 2-amino- or 2-alkylamino-1,3,4thiadiazoles is the acylation of a thiosemicarbazide or alkylthiosemicarbazides followed by dehydration in the presence of some inorganic acids, such as sulfuric acid, polyphosphoric acid or phosphorus halides [9 - 11]. 2-Amino-5-alkyl-1,3,4-thiadiazole compounds are also conventionally prepared by cyclization of a 4-alkylthiosemicarbazide and cyclodehydrating the resulting product. The cyclodehydration is customarily carried 518 out in the presence of concentrated sulfuric acid or polyphosphoric acid. Other well documented methods of cyclodehydration involve the use of polyphosphoric acid, phosphorous .
