Facile Synthesis of Some New Pyrazole-Based 2-Thioxo-4-thiazolidinone

5-Ethoxymethylene-2-thioxo-4-thiazolidinone (1) reacts with hydrazine hydrate at room temperature to afford 5-(hydrazinylmethylene)-2-thioxo-4-thiazolidinone (3). Compound 3 condensed with different aromatic aldehydes 6a–d in ethanol in the presence of a few drops of piperidine to give the corresponding Schiff’s bases 7a–d. On the other hand, compound 3 reacts with o-hydroxybenzaldehyde derivatives 8a and 8b in refluxing ethanol catalyzed by a few drops of piperidine to yield 1H-inadzolyl-2-thioxo-4-thiazolidinones 9a and 9b. Reaction of compound 3 with α-ketoesters 10a and 10b or α-diketones 10c–e in refluxing glacial acetic acid furnished the pyrazolyl-2-thioxo-4-thiazolidinone derivatives 11a–e. Also, compound 3 reacts with some different enaminones 12a–f in refluxing glacial acetic acid to afford the new pyrazolyl-2-thioxo-4-thiazolidinone derivatives 13a–f. Pyrazoles 15a–d was obtained via reaction of compound 3 with chalcones 14a–d in dimethylformamide (DMF). The structures of all the newly synthesized products were confirmed on the basis of their elemental and spectral data, and a plausible mechanism has been postulated to account for their formation.

5-乙氧基亚甲基-2-硫代-4-噻唑烷二酮(1)（5-Ethoxymethylene-2-thioxo-4-thiazolidinone）与水合肼在室温下反应，得到5-肼基亚甲基-2-硫代-4-噻唑烷二酮(3)（5-(hydrazinylmethylene)-2-thioxo-4-thiazolidinone）；化合物3与不同的芳香醛6a~d在乙醇中，滴加少量哌啶催化缩合，得到相应的希夫碱(Schiff base)7a~d。另一方面，化合物3与邻羟基苯甲醛衍生物8a、8b在回流乙醇中以少量哌啶催化反应，得到1H-吲唑基-2-硫代-4-噻唑烷二酮类化合物9a和9b。化合物3与α-酮酸酯10a、10b或α-二酮10c~e在回流冰醋酸中反应，得到吡唑基-2-硫代-4-噻唑烷二酮类衍生物11a~e；此外，化合物3与不同的烯胺酮12a~f在回流冰醋酸中反应，得到新型吡唑基-2-硫代-4-噻唑烷二酮类衍生物13a~f。吡唑类化合物15a~d可通过化合物3与查尔酮14a~d在N,N-二甲基甲酰胺(dimethylformamide, DMF)中反应制得。所有新合成产物的结构均通过元素分析与光谱数据得以确证，同时本文提出了合理的反应机理以阐释其生成过程。