Reaction of 2-oxoindolin-3-ylidene derivatives with heterocyclic enamines, a convenient one-pot synthesis of pyrimido [5,4:5′,6′]pyrido[2,3-b]indole-2, 4-dione and spiro indolin-2-one-3, 5′-pyrido [2,3-d] pyrimidines

The reaction of 6-aminouracils 2a, b with 2-oxoindolin-3-ylideneacetophenones la-h afforded Pyrimido[5,4:5', 6'] pyrido-[2, 3-b] indole- 2, 4-diones 3 a-k via a regiospecific Michael addition, followed by cyclization, Alternatively, the reaction of 2a with 2-oxoindolin-3-ylidenemalononitriles 6a, b gave rise to regiospecific formation of spiro indolin-2-one-3, 5'-pyrido[2,3-d]pyrimidines 7a,b.