Preparation of Indolenines via Nucleophilic Aromatic Substitution

An unusual aromatic substitution to access indolenines is described. 2-(2-Methoxyphenyl)­acetonitrile derivatives are reacted with various alkyl and aryl Li reagents to furnish the corresponding indolenine products, constituents of natural products, and cyanine dyes such as indocyanine green. This new method was used to synthesize 41 indolenines with large functional group tolerance, and selected examples were further converted to the corresponding indolenine dyes. Key experiments provide insight into the mechanism of this nucleophilic aromatic substitution.