An efficient iron-catalyzed C3-selective formylation of free (N–H) or N-substituted indoles was developed by employing formaldehyde and aqueous ammonia, with air as the oxidant. This new method gave 3-formylindoles in moderate to excellent yields with fairly short reaction times. Moreover, this procedure for catalytic formylation of indoles can be applied to gram-scale syntheses.

中文翻译：

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铁催化的吲哚与甲醛和氨水在空气下的 C3-甲酰化反应

通过使用甲醛和氨水，以空气作为氧化剂，开发了一种有效的铁催化的游离 (N-H) 或 N-取代吲哚的 C3 选择性甲酰化。这种新方法以相当短的反应时间以中等至极好的收率得到 3-甲酰基吲哚。此外，这种吲哚催化甲酰化过程可应用于克级合成。