Synthesis of beta- and gamma-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.