Methyl 2‐benzoylamino‐3‐dimethylaminopropenoate in the synthesis of fused pyranones. The synthesis of derivatives of tetrahydro‐2 H ‐1‐benzopyran‐2‐one, isomeric 2 H ‐naphtho[1,2‐ b ]pyran‐2‐one and 3 H ‐naphtho[2,1‐ b ]pyran‐3‐one, pyrano[3,2‐ c ]benzopyran‐2,5‐dione, and 7 H ‐pyrano[2,3‐ d ]pyrimidin‐7‐one

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‐2 H ‐1‐benzopyran‐2‐one derivative 17 , in acetic acid to afford the corresponding 3‐benzoylamino substituted 5‐oxo‐5,6,7,8‐tetrahydro‐2 H ‐1‐benzopyran‐2‐ones 5–7 , and 2 H ,5 H ‐pyrano[3,2‐c][1]benzopyran‐2,5‐dione derivative 18 . 1‐Naphthol ( 12 ) and 2‐naphthol ( 13 ) produce the isomeric 2 H ‐naphtho[1,2‐ b ]pyran‐2‐one ( 14 ) and 3 H ‐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(4 H )‐oxazolone ( 10 ). 4,6‐Dihydroxypyrimidine derivative 19 affords in acetic acid the noncyclized intermediate 20 , which can be further transformed in polyphosphoric acid into 7 H ‐pyrano[2,3‐ d ]pyrimidin‐7‐one derivative 21 .