Stereocontrolled Synthesis of β-Lactams within [2]Rotaxanes: Showcasing the Chemical Consequences of the Mechanical Bond

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• 作者：Alberto Martinez-Cuezva ; Carmen Lopez-Leonardo ; Delia Bautista ; Mateo Alajarin ; Jose Berna
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：July 20, 2016
• 年：2016
• 卷：138
• 期：28
• 页码：8726-8729
• 全文大小：369K
• 年卷期：0
• ISSN：1520-5126

文摘

The intramolecular cyclization of N-benzylfumaramide [2]rotaxanes is described. The mechanical bond of these substrates activates this transformation to proceed in high yields and in a regio- and diastereoselective manner, giving interlocked 3,4-disubstituted trans-azetidin-2-ones. This activation effect markedly differs from the more common shielding protection of threaded functions by the macrocycle, in this case promoting an unusual and disfavored 4-exo-trig ring closure. Kinetic and synthetic studies allowed us to delineate an advantageous approach toward β-lactams based on a two-step, one-pot protocol: an intramolecular ring closure followed by a thermally induced dethreading step. The advantages of carrying out this cyclization in the confined space of a benzylic amide macrocycle are attributed to its anchimeric assistance.