Laser Flash Photolysis Studies on Radical Monofluoromethylation by (Diarylamino)naphthalene Photoredox Catalysis: Long Lifetime of the Excited State is Not Always a Requisite.

Organic photoredox catalysis has become a useful tool for the development of metal-free radical reactions. Recently, we have reported that 1,4-bis(diphenylamino)naphthalene serves as an efficient photoredox catalyst for radical monofluoromethylation with -tosyl--monofluoromethyl--phenylsulfoximine . In this paper, we report the preparation and photo- and electrochemical properties of (diarylamino)naphthalene derivatives, 1,4-bis(di(--butylphenyl)amino)naphthalene , 1,5-bis(di(--butylphenyl)amino)naphthalene , and 1-(di(--butylphenyl)amino)naphthalene) , as supported by density functional theory (DFT) and time-dependent-DFT calculations. In addition, their performance of photocatalysis has been evaluated by means of methoxy-monofluoromethylation of aromatic alkenes. Laser flash photolysis shows that the fluorescence of in the excited state is efficiently quenched by (quenching rate constant = 2 × 10 M s). Transient absorption spectroscopic analyses reveal that the excited species of in the presence of starts decreasing in 100 ps, suggesting the occurrence of fast electron-transfer processes. These results lead to the unconventional concept for the catalyst design, that is, long lifetime of the excited state is not always a requisite for efficient photoredox catalysts.