Premium
Ring transformations of 4 H ‐pyrans. Pyridines from 2‐amino‐4 H ‐pyrans
Author(s) -
Seoane Carlos,
Soto José L.,
Zamorano Pilar,
Quinteiro Margarita
Publication year - 1981
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570180216
Subject(s) - chemistry , reagent , ammonium acetate , acetic acid , ring (chemistry) , cyanoacetamide , sulfuric acid , medicinal chemistry , ammonium , organic chemistry , high performance liquid chromatography
Ring transformations of 4 H ‐pyrans into pyridines are reported. Treatment of 2‐amino‐4,6‐diaryl‐3,5‐dicyano‐4 H ‐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‐4 H ‐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).