Reactions of 3‐oxo‐2,3‐dihydrobenzofuran with alkyl 2‐cyano‐3‐alkoxypropenoate and alkyl 2‐alkoxycarbonyl‐3‐alkoxypropenoate. Synthesis of pyran derivatives

Abstract 3‐Oxo‐2,3‐dihydrobenzofuran reacted with ethyl 2‐cyano‐3‐ethoxypropenoate, methyl 2‐cyano‐3‐methoxy‐propenoate affording compounds 3 (2‐(2‐cyano‐2‐alkoxycarbonylvinyl)‐3‐hydroxybenzofuran) obtained as a mixture of Z + E isomers. Methyl 2‐methoxycarbonyl‐3‐methoxypropenoate gave compound 4. Malonic compounds added on 2‐dimethylaminomethylene‐3‐oxo‐2,3‐dihydrobenzofuran 6 for giving compound 3 or 2‐oxo‐3‐methoxycarbonyl‐2H‐pyrano[3,2‐b]benzofuran 8. Compound 8 was also obtained by heating compound 4 in xylene.