A Divergent and Selective Synthesis of Isomeric Benzoxazoles from a Single N鈥揅l Imine

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• 作者：Cheng-yi Chen ; Teresa Andreani ; Hongmei Li
• 刊名：Organic Letters
• 出版年：2011
• 出版时间：December 2, 2011
• 年：2011
• 卷：13
• 期：23
• 页码：6300-6303
• 全文大小：717K
• 年卷期：v.13,no.23(December 2, 2011)
• ISSN：1523-7052

文摘

A divergent and regioselective synthesis of either 3-substituted benzisoxazoles or 2-substituted benzoxazoles from readily accessible ortho-hydroxyaryl N鈥揌 ketimines is described. The reaction proceeds in two distinct pathways through a common N鈥揅l imine intermediate: (a) N鈥揙 bond formation to form benzisoxazole under anhydrous conditions and (b) NaOCl mediated Beckmann-type rearrangement to form benzoxazole, respectively. The reaction path also depends on the electronic nature of the aromatic ring, with the electron-rich aromatic rings favoring the rearrangement and the electron-deficient rings favoring the N鈥揙 bond formation. A Beckmann-type rearrangement mechanism via net [1,2]-aryl migration for the formation of 2-substituted benzoxazole is proposed.