One-pot rapid and efficient synthesis of new spiro derivatives of 11H-indeno[1,2-b] quinoxalin-11-one, 6H-indeno[1,2-b] pyrido [3,2-e]pyrazin-6-one and isatin-based 2-pyrazolines

Some new spiro derivatives (5a-h, 9a-c and 13a-c) of 11H-indeno[1,2-b]quinoxalin-11-ones 1a-b and 6H-indeno[1,2-b]pyrido[3,2-e]pyrazin-6-one 6 and isatin 10 were synthesized by two different pathways. The chalcones 4a-h, 8a-c and 12a-c were prepared by the reaction of acetophenone and its four derivatives with 1a-b, 6 and 10 via base-catalyzed condensation followed by addition of acid. In the first procedure, the chalcones were isolated and reacted with hydrazine hydrate to give products. In the second procedure, the chalcones were in situ reacted with hydrazine hydrate without isolation to give spiro compounds in improved yields.