Synthesis of indoloquinazoline alkaloids using cascade reactions

We describe the total synthesis of indolo [2,1-6] quinazoline alkaloids tryptanthrin (1a), candidine (2), phaitanthrins A (3), B (4), C (5), cruciferane (8), and cephalanthrin A (9) using oxidative cascade sequences as the key step. Phaitanthrin E (7a) was synthesized by a novel methodology that features a concise approach involving the intermolecular condensation and intramolecular aryl C-H amination mediated by Cu-complexes to construct the indolo [2,1-6] quinazoline core. Moreover, an acid catalyzed one-pot synthesis of phaitanthrin E (7a) via intermolecular amination/intramolecular cyclization cascade using NCS was also developed.