Synthesis of β- and γ-Carbolines by the Palladium-Catalyzed Iminoannulation of Internal Alkynes

[reaction: see text] A variety of substituted beta- and gamma-carbolines have been prepared in good to excellent yields by the annulation of internal acetylenes by the tert-butylimines of N-substituted 3-iodoindole-2-carboxaldehydes and 2-haloindole-3-carboxaldehydes, respectively, in the presence of a palladium catalyst.