InCl3-mediated addition of indole to isatogens: an expeditious synthesis of 13-deoxy-isatisine A.

A strategy directed towards the total synthesis of isatisine A that involves several late-stage metal-catalyzed transformations that address the key carbon-carbon and carbon-heteroatom bond formations has been developed. As a part of this strategy, methods for the addition of indoles to isatogens that lead selectively to either 2,2-disubstituted N-hydroxyindolin-3-one or 2,2-disubstituted indolin-3-one compounds have been developed by employing InCl(3) as a catalyst or as the reagent. The present methods provide the first examples of the additions of indoles to the isatogen nucleus. To demonstrate its viability, the synthesis of 13-deoxy-isatisine A has been completed in ten steps from a known and easily available lactone.