Regioselective metalation of gamma-carbolines

The synthesis of new 3-substituted gamma-carbolines is described and these products were subjected to ortho-lithiation experiments. Whereas 3-carboxam ido derivatives (5a,b) were cleanly lithiated at 4-position, the 3-amino de rivatives (6a,b) gave only small amounts of addition products. The results obtained are compared to those previously published in the alpha-carboline series and semiempirical calculations were performed. Various 3,4-disubstit uted gamma-carbolines were obtained in acceptable yields.