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Probing the Reactivity of Cyclic N,O-Acetals versus Cyclic O,O-Acetals with NaBH4 and CH3MgI
Journal of Chemical Education ( IF 3 ) Pub Date : 2018-05-09 00:00:00 , DOI: 10.1021/acs.jchemed.7b00734
James A. Ciaccio 1 , Shahrokh Saba 1 , Samantha M. Bruno 1 , John H. Bruppacher 1 , Alexa G. McKnight 1
Affiliation  

An operationally straightforward, project-like laboratory experiment has been developed in which students directly compare the reactivity of two heterocycles, a cyclic O,O-acetal (standard C═O protecting group) and a cyclic N,O-acetal (oxazolidine), toward sodium borohydride and methylmagnesium iodide. Students synthesize a substrate containing both structural features, and then experimentally establish the chemo- and regioselective ring-opening of the N,O-acetal by identifying their 2-amino-1-alkanol products through spectral analysis. This experiment demonstrates that nonaromatic N- and O-heterocycles beyond those usually encountered by students in introductory organic textbooks, such as O,O-acetals and epoxides, are also reactive to nucleophiles, and it emphasizes the great effect on chemical reactivity of a seemingly minor structural alteration: exchanging O for N in a heterocycle.

中文翻译:

用NaBH 4和CH 3 MgI探讨环状N,O-缩醛与环状O,O-缩醛的反应性

已开发出一种操作简单,类似项目的实验室实验,学生可以直接比较两个杂环的反应性,即环状O,O-缩醛(标准C═O保护基)和环状N,O-缩醛(恶唑烷),朝向硼氢化钠和甲基碘化镁。学生合成包含两种结构特征的底物,然后通过光谱分析鉴定其2-氨基-1-链烷醇产物,通过实验建立NO-缩醛的化学和区域选择性开环。该实验表明,非芳香族N-O-杂环超出了学生在有机入门书中通常遇到的杂环,例如OO-乙缩醛和环氧化物,也对亲核试剂具有反应性,它强调了看似较小的结构变化对化学反应性的巨大影响:将O交换为N杂环。
更新日期:2018-05-09
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