Abstract An efficient protocol for the stereoselective synthesis of pyrazolo[5,1-b]thiazole-3-carboxylate tethered β-lactam conjugates 8a–j from novel pyrazolo [5,1-b]thiazole-3-carboxylate substituted Schiff’s bases 6a–f is reported here. The reaction between various ketene precursors and novel Schiff’s bases 6a–f afforded exclusive formation of trans-β-lactams 8a–j. The substrate scope of this approach was investigated extensively by varying different groups (R, Z). All the novel compounds were characterized using various spectroscopic techniques, such as FT-IR, 1H NMR, 13C NMR, elemental analysis, 13C NMR (DEPT-135), and mass spectrometry in representative cases. Single crystal X-ray crystallographic study of trans-ethyl 7-(1-(4-methoxyphenyl)-4-oxo-3-phenoxyazetidin-2-yl)-6-methyl-2-(methylthio)pyrazolo[5,1-b]thiazole-3-carboxylate 8a has confirmed the molecular structure and the stereochemical outcome. To the best of our knowledge, the synthesis of such types of Schiff’s bases and β-lactam conjugates has not been reported so far. Graphical Abstract

中文翻译：

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trans-3-functionalized-4-pyrazolo[5,1-b]thiazole-3-carboxylate 取代的β-内酰胺的立体选择性合成：多种生物活性剂的潜在合成子

摘要 从新型吡唑并[5,1-b]噻唑-3-羧酸酯取代的席夫碱6a-立体选择性合成吡唑并[5,1-b]噻唑-3-羧酸酯系β-内酰胺缀合物8a-j的有效方案f 在这里报告。各种乙烯酮前体与新型席夫碱 6a-f 之间的反应提供了反式-β-内酰胺 8a-j 的独家形成。这种方法的底物范围通过不同的不同组 (R, Z) 进行了广泛研究。所有新化合物均使用各种光谱技术进行表征，例如 FT-IR、1H NMR、13C NMR、元素分析、13C NMR (DEPT-135) 和质谱分析。trans-乙基7-(1-(4-甲氧基苯基)-4-oxo-3-phenoxyazetidin-2-yl)-6-methyl-2-(methylthio)pyrazolo[5, 1-b]thiazole-3-carboxylate 8a 已经证实了分子结构和立体化学结果。据我们所知，迄今为止尚未报道此类席夫碱和 β-内酰胺缀合物的合成。图形概要