Reaction of ketenes with N,N-disubstituted α-aminomethyleneketones. XVI. Synthesis of N,N-disubstituted 4-amino-5,6-tetramethylene-3-phenyl-2-pyranones

1,4-Cycloaddition of phenylchloroketene (prepared in situ from α-chlorophenylacetyl chloride and triethyl-amine) to a number of N,N-disubstituted (E)-2-aminomethylenecyclohexanones gave the corresponding adducts, namely N,N-disubstituted 4-amino-3-chloro-3,4,5,6,7,8-hexahydro-2H-1-benzopyran-2-ones III in the case of aliphatic N,N-disubstitution or aromatic N-monosubstitution. Purification of III was possible only in the case of IIIh (NR₂ = NMePh), therefore they were dehydrochlorinated in situ with DBN to give the title compounds in moderate overall yields.