The synthesis of 3-and 4-fluorofuroxansi sr eported for the first time. Underp hotoirradiation 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.

Nitric oxide (NO) has a range of biological activities in living systems. Because NO is a gaseous and short-lived molecule, the development of methods to enable a temporally and spatially resolved NO supply has been a challenging task. In this report, 3-aryl 4-alkoxy furoxan is revealed as a potent photo-induced NO-donor. While negligible levels of NO release were observed under ambient fluorescent light, a significant amount of NO was released under UV irradiation ( = 300-400 nm). The thiol mediator bearing a pendant amino group proved indispensable for the NO release from aryl alkoxy furoxans. Analysis of the NO-releasing reaction of aryl alkoxy furoxan revealed that the main coproduct is the corresponding aryl nitrile derived from furoxan ring-fragmentation. From these results, a plausible photo-induced NO-releasing mechanism was proposed, in which the key steps are nucleophilic attack by the thiol at the 3position of furoxan leading to the furoxan ring-fragmentation, and the formation of tetrahydrothiazole bearing a C-nitroso group. Comparison between fluorofuroxan and alkoxy furoxan is also discussed.