Divergent Synthesis of Methylisatoid and Tryptanthrin Derivatives by Ph<inf>3</inf>P-I<inf>2</inf>-Mediated Reaction of Isatins with and without Alcohols

Abstract

© 2020 American Chemical Society A novel phosphonium-mediated reaction of isatins is described. In the presence of alcohol, the reaction proceeds to furnish C-12 modified tryptanthrin derivatives. Without alcohol, self-dimerization of isatins gives rise to tryptanthrin and its analogs. This divergent and step-economic approach provides a facile access to diverse indoloquinazoline structures including the natural alkaloids, methylisatoid and cephalanthrin B, in high yields from simple precursors under mild and metal-free reaction conditions.