2,6-Dimethyl 3,5-diphenyl-4H pyran

Used for the preparation of 2,6-dimethyl-3,5-diphenyl-4H-pyrane-4-one and tetraphenylcyclopentadienone. 

Pyrones. A soln. of l,3-diphenyl-2-propanone, acetic acid, and polyphosphoric acid refluxed 1.5 hrs. at 140-150 crude 2,6-dimethyl-3-5-diphenyl-4H-pyran-4-one, Y 76%.— This reaction is a simple route to 4-pyrones and, in certain cases, to benzoIa]fluorcnones. F. e. s. R. L. Letsinger and J. D. Jamison, Am. Soc. 83, 193 (1961). 

Propanol with magnesium in reduction of chlorobenzene, 47, 104 Propionyl fluoride, 46, 6 n Propylamine, 46, 85 n Propylhydrazine, 46, 85 C ( Propyl) N phenylmtrone, genera tion from phenylhydroxylamme and n butyraldehyde, 46, 97 Purification of tetrahydrofuran (Warning), 46,105 4H Pyran 4-one, 2 6 dimethyl 3,5 diphenyl, 47, 54... 

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). 

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