Visible-light photoredox catalysis: direct synthesis of fused β-carbolines through an oxidation/[3 + 2] cycloaddition/oxidative aromatization reaction cascade in batch and flow microreactors

Abstract

Fused β-carbolines were synthesized via a visible light photoredox catalyzed oxidation/[3 + 2] cycloaddition/oxidative aromatization reaction cascade in batch and flow microreactors. Several structurally diverse heterocyclic scaffolds were obtained in good yields by coupling of tetrahydro-β-carbolines with a variety of dipolarophiles under photoredox multiple C–C bond forming events. The photoredox coupling of tetrahydro-β-carboline with 1,4-benzoquinone was significantly faster in continuous flow microreactors and the desired products were obtained in higher yields compared to batch reactors.