REACTIONS OF DEHYDROACETIC ACID AND RELATED PYRONES WITH SECONDARY AMINES

A study of the reactions of dehydroacetic acid (1) and related pyrones with secondary amines has been undertaken. Pyrrolidine reacts readily with dehydroacetic acid (1), 3-propionyl-4-hydroxy-6-methyl-2-pyrone (6), and 3-benzoyl-4-hydroxy-6-methyl-2-pyrone (10) to yield 3, 7, and 12, the respective products of nucleophilic attack at the 6 position of the pyrone, followed by ring opening and decarboxylation; with 3-acetyl-4-hydroxy-6-phenyl-2-pyrone (14) and dehydrobenzoylacetic acid (16), it gives in each case the product of condensation at the carbonyl of the side chain. Reaction of enediones 3 and 7 with pyrrolidine gives the corresponding dienones 4 and 9 which could also be obtained directly from dehydroacetic acid (1) and 3-propionyl-4-hydroxy-6-methyl-2-pyrone (6) and excess pyrrolidine. Enedione 12, however, gives 13, the pyrrolidinamide of benzoylacetic acid, when treated with pyrrolidine. When morpholine and diethylamine are employed as amines, a more complex reaction produces in the case of dehydroacetic acid (1) not only enediones and dienones but also acetoacetamides formed by attack at the 2 position of the pyrone. Mechanisms for these various transformations are discussed. © 1969, American Chemical Society. All rights reserved.