A facile one-pot cascade reaction for the synthesis of pyrazinone-fused pyridones has been developed without a metal catalyst. Hydroamination of the Ugi propargyl adducts arising from aromatic isocyanides would be promoted by the intramolecular protonation of the alkyne with the amide NH to form an unstable oxazolopyridinium. The cascade reaction was applied to alkyl isocyanide to synthesize pyrazinone-fused pyridones under strongly acidic conditions. This novel cascade reaction proceeds through an Ugi/Michael/Retro-Michael reaction, aromatization, and 5-exo-dig cyclization cascade sequence. The reaction features a simple operation procedure, one purification step, and good yields, which could be applicable to a broad scope of Ugi starting materials. This is the first report on the intramolecular hydroamination occurring between an amide and an alkyne under conditions with an organic base.

中文翻译：

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一种简洁且出乎意料的一锅法合成吡嗪酮融合的吡啶酮

在没有金属催化剂的情况下，已经开发出一种容易的一锅级联反应，用于合成吡嗪酮稠合的吡啶酮。由炔基与酰胺NH的分子内质子化作用形成不稳定的恶唑并吡啶鎓，可促进由芳族异氰化物引起的Ugi炔丙基加合物的加氢胺化。在强酸性条件下，将该级联反应应用于烷基异氰化物以合成吡嗪酮稠合的吡啶酮。这种新颖的级联反应通过Ugi / Michael / Retro-Michael反应，芳香化和5- exo-dig进行环化级联序列。该反应具有简单的操作程序，一个纯化步骤和良好的收率，其可适用于广泛的Ugi起始原料。这是关于在具有有机碱的条件下酰胺和炔烃之间发生分子内加氢胺化的首次报道。