REACTION OF KETENES WITH N,N-DISUBSTITUTED ALPHA-AMINOMETHYLENEKETONES .8. SYNTHESIS OF N,N-DISUBSTITUTED 4-AMINO-3-CHLORO-6-PHENYL-2H-PYRAN-2-ONES

The dipolar 1,4‐cycloaddition of dichloroketene to N,N‐disubstituted 3‐amino‐1‐phenyl‐2‐propene‐1‐onesled directly to N,N‐disubstituted 4‐amino‐3‐chloro‐6‐phenyl‐2H‐pyran‐2‐ones only in the case of an usual aliphatic N,N‐disubstitution. In the case of partial or full aromatic N‐substitution, N,N‐disubstituted 4‐amino‐3,3‐dichloro‐3,4‐dihydro‐6‐phenyl‐2H‐pyran‐2‐ones were instead obtained, which were dehydrochlorinated with DBN to the corresponding 4‐amino‐3‐chloro‐6‐phenyl‐2H‐pyran‐2‐ones. Copyright © 1979 Journal of Heterocyclic Chemistry