Divergent Reactivity of N-Isocyanates with Primary and Secondary Amines: Access to Pyridazinones and Triazinones

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• 作者：Joshua S. Derasp ; Jean-François Vincent-Rocan ; André M. Beauchemin
• 刊名：Organic Letters
• 出版年：2016
• 出版时间：February 19, 2016
• 年：2016
• 卷：18
• 期：4
• 页码：658-661
• 全文大小：341K
• ISSN：1523-7052

文摘

Cascade reactions for the synthesis of 1,2,4-triazinones and 5-aminopyridazinones are reported using α-ketocarbazones as N-isocyanate precursors and exploiting the divergent reactivity observed with primary and secondary amines. Triazinones were formed with primary amines, likely through addition of the amine on the N-isocyanate, followed by cyclization (condensation) on the ketone. In contrast, such cyclization is impossible for secondary amines; this allows in situ formation of enamines, which, upon cyclization, generate 5-amino pyridazinones. This sequence further illustrates the versatility of N-isocyanates in heterocyclic synthesis and provides a rare example of carbon nucleophiles reacting with N-isocyanates.