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[摘要]：4,7-Dimethylbenzofurazan 1 was more reactive than other dimethylbenzofurazans, methylbenzofurazans and benzofurazan for short duration irradiation using a Xe lamp (Pyrex filter). Compound 1 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 2 in CDCl3 at room temperature in excellent yield. With increasing temperature, the isomeric opened form compound 2 is thought to be thermally reverted to the original benzofurazan structure. The rate constant for this recyclization of 2 to 1 using CHCl3 at 293 K was 1.16 x 10(-5) s(-1). Irradiation of 1 in CDCl3 yields. photoproduct compound 2 with a quantum yield of 0.48, and a chemical yield of 99%. The yield of this photoreaction was dependant on the laser power and exposure time. |
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