The Madelung synthesis is a base-promoted intramolecular cyclization of an N-acyl-o-alkylaniline to an indole. A strong base removes a benzylic proton from the ortho-alkyl substituent, producing a carbanion that attacks the amide carbonyl intramolecularly. Cyclization followed by dehydration and rearomatization forms the five-membered pyrrole portion of the indole. Reviews of indole synthesis classify the classical Madelung reaction as a strong-base cyclization of an ortho-alkylated anilide ^[1]. Modified procedures use lithiation of N-(2-alkylphenyl)alkanamides to permit cyclization under milder conditions ^[2]. The substrate relationship—an amide nitrogen attached to an aryl ring bearing an ortho carbon nucleophile—and formation of the new carbon–carbon bond to the amide carbonyl define the reaction. It is distinct from Fischer indole synthesis from arylhydrazones and from pyrrole syntheses involving 1,3-dicarbonyl compounds and aldehydes.