Chemical and Biochemical Reactions of Aromatic Furazan Compounds

Abstract

Aromatic furazan has numerous pharmacologic and industrial applications. As part of our work on aromatic furazan chemistry and biochemistry, benzofurazan N-oxides, on irradiation using a high-pressure mercury lamp with a Pyrex filter in acetonitrile containing a little water, afforded 1H-azepine-2,7-dione. Mechanistic studies on the photoreaction using a low-pressure mercury lamp and photosensitizer suggest that photosensitized formation of 1H-azepine-2,7-dione with the aromatic hydrocarbon may be carried out by reabsorption of fluorescence. Quinoxaline 1,4-dioxide, phenazine 5,10-dioxide, and pyrido[2,3-b]pyrazine derivatives were synthesized from the corresponding aromatic or heteroaromatic furazan N-oxides by silica gel or molecular sieves under solvent-free conditions using microwave irradiation. The toxicities of some benzofurazans were examined on Escherichia coli; these may due to their reduction within the E. coli cell and their reoxidization by molecular dioxygen to form superoxide and hydrogen peroxide. The formation of 4,7-dicyanobenzofurazan anion radical in the E. coli cell suspension-4,7-dicyanobenzofurazan-glucose system in the absence of O2 was followed by ESR spectroscopy. 4,7-Dimethylbenzofurazan was transformed by 1O2 produced by irradiation of C60 into 4,7-dimethylbenzofurazan 4,7-endoperoxide. The endoperoxide decomposed back to 4,7-dimethylbenzofurazan at room temperature. 4,7-Dimethylbenzofurazan was transformed by irradiation with the third harmonic of a Quanta-Ray Nd:YAG laser (355 nm) into (2Z,4Z)-2,5-dimethylhexa-2,4-dienedinitrile monoxide. Irradiation of 4,7-dimethylbenzofurazan yielded a photoproduct with a quantum yield 0.48 and chemical yield 99%.