Madelung吲哚合成（马德隆吲哚合成）是 N-(取代)苯基酰胺与强碱（氨基钠、叔丁醇钾、丁基锂或乙醇钠）在高温隔绝空气共热，发生分子内环化生成吲哚衍生物的反应。

若 N-甲酰基邻甲苯胺发生分子内环化，则得到吲哚。

这个反应也可得到5、7-位有烷基取代基的吲哚， 但不能用于制备硝基 和卤代 吲哚。环化反应的温度取决于 N-酰基邻烷基苯胺分子中取代基的性质，如果反应温度过高，则发生分解。一般来说，加热温度高于 N-酰基邻烷基苯胺熔点5～10℃以上能取得较满意的结果。

Houlihan改进法：(经过锂化)

The Madelung synthesis is a chemical reaction that produces (substituted or unsubstituted) indoles by the intramolecular cyclization of N-phenylamides using strong base at high temperature. The Madelung synthesis was reported in 1912 by Walter Madelung, when he observed that 2-phenylindole was synthesized using N-benzoyl-o-toluidine and two equivalents of sodium ethoxide in a heated, airless, reaction. Common reaction conditions include use of sodium or potassium alkoxide as base in hexane or tetrahydrofuran solvents, at temperatures ranging between 200-400 °C. A hydrolysis step is also required in the synthesis. The Madelung synthesis is important because it is one of few known reactions that produce indoles from a base-catalyzed thermal cyclization of N-acyl-o-toluidines. The overall reaction for the Madelung synthesis follows.