Divergent Construction of N‐Doped Polycyclic Aromatic Hydrocarbons with Indole as the Nitrogen Source Building Block

Abstract

AbstractAn Ag/Au‐catalyzed divergent cascade reaction of alkyne embedded diazoketones with indoles has been described. Preliminary mechanistic studies indicate that the reaction goes through a [4+2]‐cycloaddition of an in situ formed isobenzopyrylium intermediate with indole, followed by a sequential retro‐Michael addition/carbene N−H insertion process to give the benzo[i]phenanthridines products with gold catalysis; whereas a dearomatization/rearomatization sequence occurs favourably when the reaction is catalyzed by a silver catalyst, delivering benzo[b]carbazoles in generally high to excellent yields. Notably, this is a rare example of using indole as the dienophile for cycloaddition with the isobenzopyrylium species, providing a concise and practical approach for the selective construction of N‐doped polycyclic aromatic hydrocarbons (PAHs) with structural diversity and broad functional‐group compatibility.