Tohru Takabatake

Reaction of 4,7-dimethylbenzofurazan with singlet oxygen

Abstract 4,7-Dimethylbenzofurazan ( 1 ) was transformed by 1 O 2 produced by irradiation of C 60 into 4,7-dimethylbenzofurazan 4,7-endoperoxide ( 2 ) in CDCl 3 or CD 2 Cl 2 at 0°C in excellent yields. The endoperoxide decomposed back to 1 at room temperature. When tetramethylethylene (TME) was added to the decomposing endoperoxide at 37°C, the hydroperoxide from reaction of TME with 1 O 2 was detected. The rate constant for the reaction of 1 O 2 with 1 was determined by the quenching of 1 O 2 luminescence to be 4.8×10 3 M −1 s −1 .

SILICA GEL CATALYZED SYNTHESIS OF QUINOXALINE 1,4-DIOXIDES UNDER SOLVENT-FREE CONDITIONS USING MICROWAVE IRRADIATION

We report on the simple and quick synthesis of quinoxaline 1,4-dioxides in solvent-free conditions under microwave irradiation. Heating of various benzofuroxans and β-ketoesters or 1,3-diketones adsorbed on silica gel in a microwave oven for two minutes affords diverse biologically attractive quinoxaline 1,4-dioxides in high to excellent yields. Silica gel functions not only as support using microwave but also as catalyst and dehydration reagent.