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The condensation of 1,4-diacetyl- or 3-substituted 2,5-piperazinediones (PDO) with various salicylaldehyde derivatives in the presence of a base, such as potassium t-butoxide or triethylamine, was found to give two extremely different kinds of products: 1-acetyl-3-arylmethylene-PDO and 3-(acylamino)coumarin derivatives. The former, which has a (Z)-geometric structure, was readily converted to the latter by irradiation. Furthermore, the conversion mechanism and the structural confirmation are discussed.
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Shin et al. (1986) studied this question.
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