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Short Paper | Regular issue | Vol 85, No. 9, 2012, pp.2291-2303
Published online, 20th July, 2012
DOI: 10.3987/COM-12-12531
Enaminones as Building Blocks in Heterocyclic Preparations: Synthesis of Novel Pyrazoles, Pyrazolo[3,4-d]pyridazines, Pyrazolo[1,5-a]pyrimidines, Pyrido[2,3-d]pyrimidines Linked to Imidazo[2,1-b]thiazole System

Sobhi M. Gomha* and Hatem A. Abdel-Aziz

*Department of Organic Chemistry, Cairo University, Giza-Haram 12613, Egypt

Abstract

The unreported 2-[E-3-(N,N-dimethylamino)acryloyl]-3-methyl-5,6-diphenylimidazo[2,1-b]thiazole 3 was prepared via the reaction of 2-acetyl-3-methyl-5,6-diphenylimidazo[2,1-b]thiazole 2 with dimethylformamide dimethyl acetal (DMF-DMA). Enaminone 3 underwent regioselective 1,3-dipolar cycloaddition with nitrilimines 5a-f, to afford the corresponding pyrazoles 7a-f. The reaction of 7a,d,g with hydrazine hydrate, afforded the pyrazolo[3,4-d]pyridazines 8a-c, respectively. Enaminone 3 also reacted with a hydrazines, hydroxylamine hydrochloride, 5-aminopyrazole 11, 6-aminothiouracil 15 and hippuric acid 22. The structures of the newly synthesized compounds were confirmed by spectral data and elemental analyses.