First Total Synthesis of 9-Hydroxy-8H-pyrano[3,2-f]indol-2-one

Article abstract of DOI:10.1002/jhet.2251

A simple and efficient approach to synthesize a novel pyrrolocoumarin 9-hydroxy-8H-pyrano[3,2-f]indol-2-one (7) has been described. Starting from vanillin, the key intermediate 7-methoxy-1H-indol-6-yl propiolate (6) was synthesized in six steps. Then, the target compound was obtained by forming pyrone-ring and demethylation simultaneously in one step. A plausible mechanism invoking PtCl₄ catalyzed one-step reaction of cyclization and demethylation was also presented.