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)-2H-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)-2H-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)-2H-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)-2H-pyran-2-ones.