Methyl 2‐benzoylamino‐3‐dimethylaminopropenoate (1) reacts with carbocyclic and heterocyclic 1,3‐diketones or potential 1,3‐diketones, such as 1,3‐cyclohexanediones 2–4, and 4‐hydroxy‐2H‐1‐benzopyran‐2‐one derivative 17, in acetic acid to afford the corresponding 3‐benzoylamino substituted 5‐oxo‐5,6,7,8‐tetrahydro‐2H‐1‐benzopyran‐2‐ones 5–7, and 2H,5H‐pyrano[3,2‐c][1]benzopyran‐2,5‐dione derivative 18. 1‐Naphthol (12) and 2‐naphthol (13) produce the isomeric 2H‐naphtho[1,2‐b]pyran‐2‐one (14) and 3H‐naphtho[2,1‐b]pyran‐3‐one (15) derivatives, respectively. Ethyl cyclopentanone‐2‐carboxylate (8) and ethyl cyclohexanone‐2‐carboxylate (9) do not react under these conditions, while in polyphosphoric acid the cyclization of the reagent 1 is taking place to give 4‐dimethylaminomethylene‐2‐phenyl‐5(4H)‐oxazolone (10). 4,6‐Dihydroxypyrimidine derivative 19 affords in acetic acid the noncyclized intermediate 20, which can be further transformed in polyphosphoric acid into 7H‐pyrano[2,3‐d]pyrimidin‐7‐one derivative 21.
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