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A relay visible-light photoredox catalysis strategy has been accomplished. Three successive photoredox cycles (one oxidative quenching cycle and two reductive quenching cycles) are engaged in a single reaction with one photocatalyst. This strategy enables formal [4 + 1] annulation of hydrazones with 2-bromo-1,3-dicarbonyl compounds, which functionalizes three C-H bonds of hydrazones. This method affords rapid access to a complex and biologically important pyrazole scaffold in a step-economical manner with high efficiency under mild conditions.

The reductive single electron transfer (SET) umpolung amination of aldehyde-derived hydrazones has been developed through visible-light-promoted photoredox catalysis. The ideal transformation of hydrazones into the corresponding hydrazonamide through selective carbon-hydrogen (C-H) bond functionalization represents one of the most step- and atom-economical methods. This SET umpolung strategy features mild conditions and a remarkably broad substrate scope, offering an entirely new substrate class to direct C-H amination.

A novel visible light photoredox catalysis three-component 1,2-difluoroalkylarylation of styrenes was disclosed, and two new C–C bonds were generated in a single step through regioselective incorporation of a CF2 group and a variety of indoles to CC bonds. The well-designed photoredox system achieved the synthesis of a series of difluoro-containing indole derivatives with mild conditions and a broad substrate scope.

C-1-monofluoromethylated tetrahydroisoquinolines are obtained by visible-light photoredox-catalyzed reaction of tetrahydroisoquinolines with β-fluorinated gem-diols as CF-source under mild reaction conditions.

Visible light induced photoredox catalysis is an efficient method for radical activation. Herein, we report the photoredox catalysis involving an intramolecular radical–radical coupling reaction that proceeds through a biradical intermediate. This protocol represents a new synthetic route to construct multi-substituted N-heterocycles. Four, five and six-membered N-heterocyclic structures with a quaternary carbon center are accessible under mild conditions.

Oxazolo[3,2-a]indolone and spiro[furan-2,2′-indolin]one are synthesized by the visible-light-induced aerobic dearomative reaction of indoles. The common indole tethered alcohol at the N1 or C2 position reacts in a cascade fashion, providing facile access to diverse indolone scaffolds.

C-1-monofluoromethylated tetrahydroisoquinolines are obtained by visible-light photoredox-catalyzed reaction of tetrahydroisoquinolines with β-fluorinated gem-diols as CF-source under mild reaction conditions.