α-Azidochalcones were coupled with 1/2-naphthols or 2-hydroxy-1,4-naphthoquinone using Ru­(bpy)3­(PF6)2 as a photocatalyst under blue LED light irradiation to yield 2,3-fused pyrroles in high yields (68–84%). The overall transformation involves photosensitized decomposition of α-azidochalcones into highly reactive 2H-azirines which are trapped by 1/2-naphthols or 2-hydroxy-1,4-naphthoquinone, leading to the construction of two new C–N and one new C–C bonds.

1,2,3,4-Tetrahydro-β-carbolines were coupled with α-keto vinyl azides through an unprecedented visible light-Ru(bpy)3(PF6)2/TBHP mediated photocascade strategy that involves photosensitization, photoredox catalysis and [3 + 2] cycloaddition reaction. The scope and scale-up feasibility of the photocascade strategy was demonstrated by synthesizing 18 different fused β-carbolines in moderate to good yields using batch and continuous flow microreactor. This operationally simple synthetic protocol allows the formation of one C-C and two C-N new bonds in the overall transformation.

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 microreactor and the desired products were obtained in higher yields compared to batch reactor.