Intramolecular Fischer Indole Synthesis in Combination with Alkyne Hydroarylation: Synthesis of Tetracyclic Chromeno-indoles

Abstract

Aryl hydrazides bearing a carbonyl function connected through an alkyne tether underwent an intramolecular Fischer indolization and alkyne hydroarylation in a tandem fashion to afford novel tetracyclic chromeno-indoles. The accompanying isomerization of the 2H-chromene double bond can be avoided by stopping the tandem process at the indolophane stage and conducting the alkyne-hydroarylation reaction separately in the absence of a proton source.