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首页> 外文期刊>Chemistry: A European journal >Three- and four-membered rings from cycloadditions of 1,3-thiazolium 4-olates and aldehydes
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Three- and four-membered rings from cycloadditions of 1,3-thiazolium 4-olates and aldehydes

机译：1,3-噻唑鎓4-油酸酯和醛的环加成反应的三元和四元环

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摘要

2-Aminothioisomunchnones, a well-known family of masked dipoles, react with aromatic aldehydes in a domino cascade reaction that produces episulfides (thiiranes) or eta -lactams (2-azetidinones). This sequence is initiated by a [3+2] dipolar cycloaddition followed by ring opening of cycloadducts and intramolecular rearrangement to afford these unusual ring contractions. The nature of the reaction products depends on the structural characteristics of the starting dipole and the experimental conditions. Episulfides are obtained selectively as cis isomers with respect to both aryl groups, whereas beta -lactams are produced as cis/trans mixtures. These structural features were determined unequivocally by X-ray crystallographic analysis. The beta -lactams still possessed a flexible acyclic chain containing sulfur, a salient lead modification of the bioactive cyclic penems and cephems. The preferential production of exo transition structures was rationalized with the aid of computational calculations at the B3LYP/6-31G* level. [References: 67]
机译：2-Aminothioisomunchnones是一种众所周知的掩蔽偶极子家族，在多米诺级联反应中与芳族醛发生反应，从而产生环硫化物（噻喃类）或η-内酰胺类（2-氮杂环丁酮）。该序列由[3 + 2]偶极环加成开始，随后是环加合物的开环和分子内重排以提供这些异常的环收缩。反应产物的性质取决于起始偶极的结构特征和实验条件。相对于两个芳基，环硫化物选择性地作为顺式异构体获得，而β-内酰胺以顺式/反式混合物形式产生。通过X射线晶体学分析明确地确定了这些结构特征。 β-内酰胺类仍然具有含硫的柔性无环链，这是生物活性环状青霉素和头孢烯的显着铅修饰。借助B3LYP / 6-31G *级别的计算，合理地优化了exo过渡结构的优先生产。 [参考：67]

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