Abstract
The ring transformation of 2, 2-dimethyl-1, 3-dioxin-4-ones (1) to nitrogen heterocycles was studied. Heating of 1 with imines such as Schiff bases gave rise to [2+4] cycloadducts of imines to acylketenes (2), i.e., 3, 4-dihydro-1, 3-oxazin-4-one derivatives (4). Similarly, 1 reacted with carbodiimides to yield 2-imino-1, 3-oxazin-4-one derivatives (11 and 12). The reaction of 1 with phenyl isocyanate gave 3-phenyl-1, 3-oxazine-2, 4-diones (15), while the reaction with 2-pyridyl isocyanate gave pyrido [1, 2-a] pyrimidin-4-one derivatives (18).
