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

Abstract

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.