Preparation of Polyfunctionally Substituted Pyridine-2(1H) thione Derivatives as Precursors to Bicycles and Polycycles
Abstract
Reaction of acetylacetone with 1 mole of dimethylformamide dimethyl acetal (DMFDMA) affords enamine 2a which react with cyanothioacetamide to give pyridinethione 3a. Pyridinethione 3a reacts with methyl iodide, halogenated compounds, aromatic aldehyde and malononitrile / elemental sulfur to yiled compounds 7-10 respectively. Reactions of thioether (7) in ethanolic K2CO3, 1 mole DMFDMA and 4-(dimethylamino) benzaldehyde gave compounds (11, 13, 14) respectively. Enaminone (12) can be prepared by reaction of compound (11) with DMFDMA. Also, compounds (13) and (14) can be obtained by reaction of compounds (3a) and (9a) with 2 mole of DMFDMA and methyl iodide respectively. Reactions of enaminone (9) with hydrazine hydrate and cyanothioacetamide gave compounds (11) and (12) respectively. Malononitrile dimmer when reacted with chalcones (9a), (14) and enaminone (12), (13) gave bipyridyl (15), (16) and (19a,b) respectively. Bipyridyl (15) can be converted to (16) by methylation using methyl iodide. Reactions of thienopyridine (8) with DMFDMA and sodium nitrite in acetic acid gave tricyclic compounds (20) and (21) respectively. Finally, reactions of (21a) with malononitrile / elemental sulfur and DMFDMA gave compounds (22) and (23) respectively.
Keywords: Acetyl acetone; DMFDMA; Malononitrile dimmer; Bipyridyl; 5-Acetylpyridinethione.
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