Carbocations in the β-Lactam and β-Thiolactam Series
作者:Xavier Creary、Chen Zhu、Ziqi Jiang
DOI:10.1021/ja9624329
日期:1996.1.1
products in a process which exhibits a large solvent effect as well as large substituenteffects. A common ion rate suppression as well as largely racemic products from solvolyses of an optically active substrate all point to the involvement of β-lactam derived carbocationic intermediates. Unlike acyclic analogs, these cations are captured by solvent to give simple substitution products with no competing
3-芳基-3-羟基取代的β-硫代内酰胺和β-内酰胺的甲磺酸酯和三氟乙酸酯衍生物的溶剂分解在表现出大溶剂效应和大取代基效应的过程中进行以产生取代产物。常见的离子速率抑制以及来自旋光底物的溶剂分解的主要外消旋产物都表明涉及β-内酰胺衍生的碳阳离子中间体。与无环类似物不同,这些阳离子被溶剂捕获以产生简单的取代产物,而没有竞争性质子损失。计算研究表明,由于潜在消除产物中的抗芳香性,这些 β-内酰胺衍生的阳离子中间体的质子损失是不利的过程。计算研究还表明,这些阳离子的 CS 和 CO 共轭稳定作用很小或不存在。取代基效应研究表明,这些阳离子获得稳定的主要方式是通过芳基电荷离域。叠氮...
Hydroxy-β-Thiolactams to Oxazole-2-thiones. A Novel DMSO-Promoted Oxidation
作者:Xavier Creary、Andrea Losch
DOI:10.1021/ol802050a
日期:2008.11.6
3-Aryl-3-hydroxy-1-methylazetidine-2-thiones react with HCl in DMSO to give 3-methyl-5-aryloxazole-2-thiones. Substituenteffects correlate with rateeffects on hydrolyses of acetals of benzaldehyde. An (17)O labeling experiment indicates that the oxygen atom of the product is derived from the hydroxyl group. Trifluoroacetic anhydride/DMSO in CH2Cl2 can also promote the reaction. Mechanisms involving