Abstract
Ethyl 4-oxopyrimido [1, 6-α] pyrimidine-3-carboxylates (4) were prepared by the thermal cyclization of diethyl N-(4-pyrimidinyl) aminomethylenemalonates (3) in which no substituent was present at position 2. Some of the compounds 4 readily afforded stable covalent hydrates which proved to be ethyl 6, 7-dihydro-6-hydroxy-4-oxopyrimido-[1, 6-α] pyrimidine-3-carboxylated (9) formed by the addition of a molecule of water across the 6, 7 C=N bond in 4. This hydration was affected by the electronic character of the substituent at position 8 in the 4H-pyrimido [1, 6-α] pyrimidine ring.
