1.5- Diphenyl-l,3,5-pentanetrione

Diphenyl-l,3,5-pentanetrione (45) has proved successful in other conversions with DMroMA. When l,5-diphenyl-l,3,5-pentanetrione (45) reacted only with 1 equivalent of DMFDMA, the isolated product was pyranone 47 (Scheme 18). The structure of 47 was confirmed by single crystal X-ray analysis. 

Diphenyl-l,3,5-pentanetrione (45) with 1 equivalent of N,N-dimethylacetamide dimethyl acetal (DMADMA) yielded 5-benzoyl-2-phenil-6-methyl-4-pyranone (49). Pyranone 49 with DMFDMA yielded 50, which was converted to 2,5-diphenyl-lH,4H-pyrido[4,3- 7]pyrane-4-one (51) by cyclization of compound 50 with aqueous ammonia. This reaction was performed in DMF at 80 °C and the product precipitated from the mixture (Scheme 19). 

Reaction of l,5-diphenyl-l,3,5-pentanetrione (45) with DMFDMA was carried out in propyl acetate under reflux for 12 h, followed by removal of the solvent by vacuum distillation. The oily residue was dissolved in another solvent (usually ethanol) and cyclization with various amines under reflux in the presence of catalytic amounts of concentrated hydrochloric acid was performed to form 1-substituted 3,5-dibenzoyl 4-oxo-l,4-dihydropyridines (46) (Scheme 17). 

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