1,5-Diphenylpentane-1,3,5-trione (1) was transformed by the reaction either with N,N-dimethylformamide dimethyl acetal (DMFDMA) or N,N-dimethylacetamide dimethyl acetal (DMADMA) into (N,N-dimethylamino)-methylidene derivatives 2a,b as intermediates. They were converted in the presence of silica gel into 5-benzoyl-2-phenylpyran-4-one (3a) and its 6-methyl derivative 3b, while the corresponding 5-benzoyl- 2-phenylpyridin-4(1H)-one (4) was formed by the reaction with NH4Cl. Compound 3b gave the corresponding (N,N-dimethylamino)methylidene derivative 5 with DMFDMA, which was cyclized in aqueous ammonia into 2,5-diphenyl-4H-pyrano3,2-cpyridin-4-one (7). The reaction of 1 with excess of DMFDMA followed by reaction with ammonia or primary amines yielded 1-substituted 3,5-dibenzoylpyridin-4(1H)-ones (9a-m).
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