Reaction of primary enamines, such as 3-aminocrotononitrile (IIIa), β-aminocinnamonitrile (IIIb), 4-amino-3-penten-2-one (IIIc), and ethyl β-aminocinnamate (IIId), with ketene gives results in acylation of their enamine-carbon to give C-acetates (Va, b) or C, N-diacetates (VIc, d). Acetylation of III (a to d) with acetic anhydride gives their N-acetates (IVa-d) whose reaction with ketene does not afford C, N-diacetates (VI). On the other hand, III (a to d) reacts with diketene and their enamine-carbon and-nitrogen are both acylated, giving 2, 3-disubstituted 6-methyl-4-pyridone (VIIa-d), N-acetoacetate (IXa, b), and 2, 6-dimethyl-4-oxopyran-3-carboxamide derivatives (Xa, b). Similar results were also obtained with other enamines such as ethyl 3-aminocrotonate (IIIe), 3-amino-2-cyclohexen-1-one (IIIf), and 3-amino-5, 5-dimethylcyclohexen-1-one (IIIg).
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