Reaction of ketenes with N,N ‐disubstituted α‐aminomethyleneketones. XII. Synthesis of N,N ‐disubstituted 4‐amino‐3‐chloro‐6‐(2‐methyl‐l‐propenyl) (2‐phenylethenyl)‐2 H ‐pyran‐2‐ones

Cycloaddition of dichloroketene to N,N ‐disubstituted ( E )‐amino‐5‐methyl‐1,4‐hexadien‐3‐ones IV and ( E,E )‐1‐amino‐5‐phenyl‐1,4‐pentadien‐3‐ones V occurred in moderate to good yield only in the case of aromatic N ‐substitution to give N,N ‐disubstituted 4‐amino‐3,3‐dichloro‐3,4‐dihydro‐6‐(2‐methyl‐l‐propenyl) (2‐phenylethenyl)‐2 H ‐pyran‐2‐ones, which were dehydrochlorinated with DBN to afford in good yield N,N ‐disubstituted 4‐amino‐3‐chloro‐6‐(2‐methyl‐propenyl)(2‐phenylethenyl)‐2 H ‐pyran‐2‐ones. In the case of aliphatic N,N ‐disubstitution (dimethylamino group) of enaminones IV and V, the Cycloaddition led directly in low yield to 3‐chloro‐4‐dimethylamino‐6‐(2‐methyl‐l‐propenyl)(2‐phenylethenyl)‐2 H ‐pyran‐2‐ones.