Photolysis of ethyl diazoacetate and of ethyl diazomalonate in acetonitrile gave oxazoles. Photolysis of ethyl diazoacetate in the presence of benzophenone gave an oxazoline incorporating the elements of carbethoxymethylene. benzophenone, and acetonitrile. Photolysis of ethyl diazomalonanilate gave 5-ethoxy-2-methyl-4-phenylcarbamoyloxazole, 5-ethoxy-3-methyl-4-phenylcarbamoylisoxazole, and ethyl α-hydroxymalonanilate. With 2537 Å wavelength radiation the oxazole was formed predominantly; on the other hand, with benzophenone-sensitization, the isoxazole was formed (among other products) but no oxazole. The oxazole was isomerized to the isoxazole when irradiated in the presence of a sensitizer, while the isoxazole was isomerized to the oxazole when irradiated with radiation of 2537 Å wavelength. A tentative mechanism is advanced to explain formation of the different products.
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Buu et al. (1972) studied this question.
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