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Heterocyclic synthesis via enaminones: Regioselective synthesis of some novel pyrazole, isoxazole, pyrimidine, pyrido[1,2-a]benzimidazole and pyrazolo[1,5-a]-pyrimidine derivatives

✍ Scribed by Kamal M. Dawood; Zaghloul E. Kandeel; Ahmad M. Farag

Publisher: John Wiley and Sons
Year: 1999
Tongue: English
Weight: 164 KB
Volume: 10
Category: Article
ISSN: 1042-7163
DOI: 10.1002/(sici)1098-1071(1999)10:5<417::aid-hc12>3.0.co;2-3

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✦ Synopsis

2-Acetylbenzothiazole (1) reacts with

dimethylformamide dimethylacetal (DMF-DMA) to afford the enaminone 2. Compound 2 reacts regioselectively with some nitrilimines 5a-d and nitrile oxides 6b-d to afford the novel pyrazole and isoxazole derivatives 11a-d and 12b-d, respectively, which react with hydrazine hydrate to give the new pyrazolo [3,4d]pyridazine and isoxazolo [3,4-d]pyridazine derivatives 13a-d and 14b-d, respectively. The enaminone 2 reacts with 1H-benzimidazole-2-acetonitrile ( ) to afford the pyrido[1,2-a]benzimidazole derivatives 19. Compound 2 reacts also with 5-amino-3-phenylpyrazole (20) and with guanidine to afford the new pyrazolo [1,5-a]pyrimidine and the 2-aminopyrimidine derivatives 22 and 24, respectively.

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