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tert ‐Amino effect at a coumarin and a 2‐quinolone system: Synthesis of 1,2 fused 5 H ‐chromeno[4,3‐ b ]pyridin‐5‐ones and a 6 H ‐benzo[ h ][1,6]naphthyridin‐5‐one
Author(s) -
Ivanov Ivo C.,
Glasnov Toma N.,
Belaj Ferdinand
Publication year - 2008
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.5570450120
Subject(s) - chemistry , iminium , intramolecular force , ring (chemistry) , coumarin , knoevenagel condensation , stereochemistry , medicinal chemistry , quinolone , pyrone , redox , ion , organic chemistry , catalysis , biochemistry , antibiotics
ome novel 1,2‐fused 5 H ‐chromeno[4,3‐ b ]pyridin‐5‐ones ( 5a,b ) and a 6 H ‐benzo[ h ][1,6]naphthyridin‐5‐one ( 5c ) have been synthesized starting from the 4‐chlorocoumarin‐3‐carbaldehyde ( 1a ) or its N ‐methyl‐2‐quinolone analogue ( 1b ) via subsequent Knoevenagel condensation and ring closure reaction known as the ‘ tert ‐amino effect’. These are rare examples of the tert ‐amino effect occurring at 2‐pyrone and 2‐pyridone ring. An unusual intramolecular redox reaction of the iminium ion 6 , reported earlier, most probably follows analogous mechanism as the tert‐ amino effect reactions leading to 5 .