The synthesis of 5‐substituted 3‐benzoylamino‐6‐(2‐substituted amino‐1‐ethenyl)‐2H‐pyran‐2‐ones and their transformations into 2H‐pyrano[3,2‐c]pyridine derivatives

A new approach to the 2H‐pyrano[3,2‐c]pyridine system is described. 5,6‐Disubstituted 3‐benzoylamino‐2H‐pyran‐2‐ones 3a,b, prepared from the corresponding 1,3‐dicarbonyl compounds 1a,b and methyl (Z)‐2‐benzoylamino‐3‐dimethylaminopropenoate (2), were converted into 3‐benzoylamino‐6‐(2‐dimethylamino‐1‐ethenyl)‐5‐ethoxycarbonyl‐2H‐pyran‐2‐one (4a) and 5‐acetyl derivative 4b. The exchange of the dimethylamino group in 4a,b with aromatic amines 5a‐f,m, héteroaromatic amines 5g‐i, and benzylamines 5j‐l produced 5‐ethoxycarbonyl‐3‐benzoylamino‐6‐(2‐arylamino‐ or heteroarylamino‐or benzylamino‐1‐ethenyl)‐2H‐pyran‐2‐ones 6a‐l, and its 5‐acetyl analog 6m. The compounds 6 were cyclized in basic media into 2H‐pyrano[3,2‐c]pyridine derivatives 7a‐h. Analogously react also α‐amino acid derivatives 8a‐c and 11 as nitrogen nucleophiles producing 9a‐c, 10 and 12.