New approaches to improve Skraup-type reactions for large-scale synthesis of 1,2-dihydroquinolines (1,2-DHQs) are highly desirable yet challenging in synthetic chemistry. Herein, an efficient sodium iodide-promoted Skraup-type reaction of anilines with ketones has been developed at low loading of HBF4 (0.5 mol%), thus providing a sustainable and economical strategy for the synthesis of 1,2-DHQs. A variety of 1,2-DHQs were obtained in moderate to good isolated yields. The practicality of this strategy was well demonstrated by a hundred-gram-scale synthesis of 6-fluoro-2,2,4-trimethyl-1,2-dihydroquinoline in 68% isolated yield. Intriguingly, an unusual azetine intermediate was successfully isolated and structurally determined by NMR and MS, indicating of an unprecedented mechanism for Skraup-type quinoline synthesis.

中文翻译：

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NaI 促进通过不常见的氮杂素中间体合成二氢喹啉


在合成化学中，改进大规模合成 1,2-二氢喹啉 （1,2-DHQ） 的 Skraup 型反应的新方法非常可取但具有挑战性。在此，在 HBF4 （0.5 mol%） 的低负载下开发了一种高效的碘化钠促进的苯胺与酮的 Skraup 型反应，从而为合成 1,2-DHQs 提供了一种可持续且经济的策略。获得各种 1,2-DHQs，分离产量中等至良好。6-氟-2,2,4-三甲基-1,2-二氢喹啉的百克级合成以 68% 的分离产率很好地证明了该策略的实用性。有趣的是，一种不寻常的氮杂素中间体被成功分离出来，并通过 NMR 和 MS 进行了结构测定，这表明 Skraup 型喹啉合成具有前所未有的机制。