Reactivity of alkynylindole-2-carboxamides in [Pd]-catalysed C-H activation and phase transfer catalysis: formation of pyrrolo-diindolones vs. β-carbolinones.

The divergent behaviour of 3-alkynylindole-2-carboxamides, under palladium catalysed conditions and phase-transfer catalytic conditions, is described. Thus, palladium catalysed intramolecular C-N and C-C bond formation in a single step by C-H activation involving 3-alkynylindole-2-carboxamides and leading to pyrrolodiindolones in high yields is developed. In contrast, using the same precursors, a high yielding regio- and chemo-selective route for 3-substituted β-carbolinones by phase-transfer catalysis is established via intramolecular C-N bond formation. The structures of key products are confirmed by X-ray crystallography.