Palladium-Catalyzed C-C Ring Closure in α-Chloromethylimines: Synthesis of 1H-Indoles

The C-C ring closure of alpha-chloromethyl alkyl or aryl N-aryl imines catalyzed with 1 to 10 % Pd(OAc)(2)/P(p-tolyl)(3) afford efficiently 2-aryl- and 2-alkyl-1H-indoles. The heterocyclization reaction involves the initial formation of [2-(arylimino)ethyl]palladium(II) chloride complexes with subsequent C-H activation of the aromatic amine ring. Readily or commercially available alpha-chloromethyl-aryl or -alkyl ketones are used as the precursors. Functionalized indoles at the benzene ring are obtained when the imines are derived from substituted anilines.