Versatile Biaryls and Fused Aromatics through Oxidative Coupling of Hydroquinones with (Hetero)Arenes

Abstract

Hydroquinones bearing an electron‐withdrawing group at the C2‐position can effectively underwent oxidative coupling with (hetero)arenes (e. g., indoles, electron‐rich benzene derivatives) in the presence of 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone (DDQ) and FeCl3 to produce the corresponding biaryl products. In the present reactions, the DDQ‐mediated oxidation of hydroquinone derivatives produce benzoquinone intermediate, which subsequently underwent FeCl3‐catalyzed nucleophilic addition of (hetero)arenes to the α,β‐unsaturated carbonyl moiety to give the biaryl product in a one‐pot manner. Especially, the indole‐based biaryl products were further converted into tetracyclic aromatics through DDQ‐mediated oxidation followed by FeCl3‐catalyzed intramolecular cyclization. Thiophene derivatives were also applicable to give the tetracyclic aromatics. Moreover, the photophysical properties of the indole‐ and thiophene‐based tetracyclic aromatics in the solution and the solid states were investigated.