Synthesis of 3-methyl-4H-benzo[b][1,4]thiazine-2-carboxylates Using CAN as a Catalyst and Its Conversion Into Guanidines

Background: 1,4-benzothiazine carboxylates show wide application in the field of medicinal chemistry. Therefore, we have designed convenient and efficient method for the synthesis of 1,4-benzothiazine carboxylates. Objective: Synthesis of 1,4-benzothiazine carboxylates and its guanidines by simple and facile method using efficient catalyst. Methods: Derivatives of 1,4-benzothiazine carboxylates were synthesized by cyclocondensing β- keto esters with 2-aminobenzenethiols using CAN as a catalyst at room temperature. 1,4-benzothiazine carboxylate, condensed with guanidine hydrochloride in the presence of sodium methoxide in DMF to obtained new 3-substituted-l-4H-benzo[b][1,4]thiazine-2-carboxyguanidines (88-91%). Results: All the products were obtained with good to excellent yields within 40 min. Here, CAN oxidizes aminothiophenol into disulfide and then nucleophilic attack of enolic form of β-ketoesters on the disulphide and 1, 4-benzothiazine acetates, were obtained with good yields. Conclusion: We have designed convenient and efficient method for the synthesis of 1,4-benzothiazine carboxylates. Most remarkable features of this cyclocondensation such as use of efficient catalyst and non-volatile solvent under mild reaction condition to obtain excellent yield. </jats:sec

Ionic Liquid Catalyzed One-Pot Synthesis of 5-(4-Substituted-Phenyl)-1,3,4-Thiadiazole-2-Amines

A highly efficient ionic liquid catalyzed protocol has been investigated for the synthesis of 5-(4-substituted-phenyl)-1,3,4-thiadiazole-2-amine derivatives from the cyclocondensation of diversely substituted aromatic carboxylic acid and thiosemicarbazide by using recyclable N-methylpyridiniumtosylate as an ionic liquid. Highly efficient, inexpensive, solvent and metal free, high step and atom efficiency and excellent yield (95%–98%) are remarkable features of present protocol.</p