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.