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Ring transformations of 4H‐pyrans into pyridines are reported. Treatment of 2‐amino‐4,6‐diaryl‐3,5‐dicyano‐4H‐pyrans (I) with nitrosylsulfuric acid brings about their transformation into 3,5‐dicyano‐4,6‐diaryl‐2‐pyridones (VI) which can also be obtained from α‐benzoylcinnamonitriles (IX) and cyanoacetamide. Similarly, 2‐amino‐4,6‐diaryl‐5‐carbethoxy‐3‐cyano‐4H‐pyrans (II) lead to 4,6‐diaryl‐5‐carbethoxy‐3‐cyano‐2‐pyridones (VII). Treatment of both series of pyrans with sulfuric acid results in the formation of the corresponding 3,4‐dihydro‐2‐pyridones (IV and V). Reaction of pyrans II with ammonium acetate in acetic acid yields 2‐amino‐4,6‐diaryl‐5‐carbethoxy‐3‐cyanopyridines (XII). Pyrans I undergo an entirely different type of reaction upon treatment with this reagent leading to 2,4,6‐triaryl‐3,5‐dicyano‐1,4‐dihydropyridines (XV).

Aus dem Cyanoessigsäurehydrazid (I) und den Benzylidenmalonitrilen (II) erhält man die N‐Amino‐pyridone (III).

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