Bypassing the stereoselectivity issue: transformations of Kinugasa adducts from chiral alkynes and non-chiral acyclic nitrones
作者:Rafał Kutaszewicz、Barbara Grzeszczyk、Marcin Górecki、Olga Staszewska-Krajewska、Bartłomiej Furman、Marek Chmielewski
DOI:10.1039/c9ob00940j
日期:——
reported. Electronic circular dichroism (ECD) in combination with NMR spectroscopy was used to determine the absolute configuration of all components of complex mixtures of azetidinones. Stereochemical preferences observed in the studied reactions are discussed and a model of a new reaction pathway supported by DFT conformational analysis is proposed. Subsequent transformations of the synthesized Kinugasa
报道了通过手性乙炔铜和无环硝酮之间的反应制备β-内酰胺的方法。电子圆二色性(ECD)结合NMR光谱用于确定氮杂环丁酮复杂混合物的所有组分的绝对构型。讨论了在所研究反应中观察到的立体化学偏好,并提出了由DFT构象分析支持的新反应途径的模型。合成的Kinugasa加合物的后续转化,然后在C-3碳原子上进行差向异构化,导致立体选择性提高的反式取代氮杂环丁酮,模仿了多种重要的β-内酰胺结构。另一方面,将呋喃基残基氧化成羧基,然后用四乙酸铅氧化脱羧,得到热力学上更稳定的反式取代的4-乙酰氧基氮杂环丁酮。对于其中在C-3碳原子上具有相同构型的异构体占优势的非对映异构混合物而言,后一种策略特别有吸引力。