The synthesis of 3- and 4-fluorofuroxans is reported for the first time. Under photoirradiation and physiological conditions, 4-fluorofuroxans with weaker nitric oxide-releasing ability are converted into 3-fluorofuroxans, which show remarkable thiol-mediated nitric oxide-releasing properties, thereby suggesting that 4-fluorofuroxans are potent photoinduced nitric oxide donors.

Diverse furoxans (1,2,5-oxadiazole 2-oxides) were synthesized from the corresponding styrenes using nitrosonium tetrafluoroborate as the nitrosation reagent in pyridine (basic media) or dichloromethane (neutral media). Acid-sensitive functional groups were tolerated under these conditions. The probable reaction mechanism was elucidated. The experimental results support an ionic reaction pathway in contrast to the conventional acidic conditions with a radical mechanism.

The photoinduced persistent intramolecular charge-transfer state of 4-carbazolyl-3-(trifluoromethyl)benzoic acid was confirmed. It showed a higher catalytic activity in terms of yield and selectivity in the photochemical reduction of alkyl halides compared to the parent carbazole. Even unactivated primary alkyl bromides could be reduced by this photocatalyst. The high catalytic activity is rationalized by considering the slower backward single-electron transfer owing to the spatial separation of the donor and acceptor subunits.

We have revisited the Saito photochemical reduction and established practical reaction conditions, under which the reduction of m-(trifluoromethyl)benzoates, derived from secondary and tertiary alcohols, proceeds selectively at high concentration to afford the corresponding alkane products in good yields without formation of alkenes. A one-pot deoxygenation of alcohols to alkanes has also been developed.