Abstract
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.
Highlights
Indenoquinoxaline derivatives are important classes of nitrogen containing heterocycles and they constitute useful intermediates in organic synthesis.[18,19,20]. They have been reported for their applications in dyes and have been used as building blocks for the synthesis of organic semiconductors
Giving attention to the possible biological effects of the presence of both 2-pyrazoline and indenoquinoxaline or isatin moieties in an organic compound, it appeared useful to synthesize a series of spiroindenoquinoxalines and spiroisatins based 2-pyrazolines.As a part of our ongoing research programs in the area of heterocyclic compounds containing nitrogen, 62-69 we report a novel one-pot procedure for synthesis of some new spiro indenoquinoxalines, indenopyridopyrazines and isatins based 2-pyrazolines in good yields, via condensation of chalcones and hydrazine in acidic condition
Many of 2-pyrazoline derivatives have been synthesized in last century,[70,71,72] but these synthesized spiro derivatives have not been reported yet
Summary
Nitrogen containing heterocycles are frequently found in privileged structures (pharmacophores) 1-3 but their incorporation sometimes possess special problems (multistep sequences, lack of generality, preparation from acyclic precursors, etc.); only a limited number of strategies have been successfully applied in the synthesis of heterocyclic scaffolds.[4,5,6,7,8,9,10] The development of new, rapid, and clean synthetic routes toward focused libraries of such compounds is of great importance to both medicinal and synthetic chemists.[11,12,13,14] the designand development of procedures for the generation of new heterocycles receives growing interest.[15,16,17]Indenoquinoxaline derivatives are important classes of nitrogen containing heterocycles and they constitute useful intermediates in organic synthesis.[18,19,20] They have been reported for their applications in dyes and have been used as building blocks for the synthesis of organic semiconductors. Our aim was to prepare some new spiro compounds with spiro 2-pyrazoline ring at C-11 carbon of indenoquinoxalines 1a-b, C-6 carbon of indenopyridopyrazine 6 and C-3 carbon of isatin 10, by the reaction of chalcones with hydrazines in one-pot rapid and efficient procedure.
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