In contrast with the reaction of α-aminonitriles 1 a, the corresponding N-acylated α- aminonitriles 1 bf and oxalyl chloride do not yield pyrazinone derivatives, but 5- aminooxazoles 9-11 or 4 (5H)-imidazolones 12, the latter being converted in some cases into imidazo [2, 1-a] isoquinoline-2, 5, 6 (3H)-triones. Reactions of compounds 1 bf and ethyl chlorooxoacetate provide evidence for a 5 (4H)-iminooxazole intermediate 7, which ...