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The reaction of homophthalic acid and some aza analogues with vilsmeier reagent: a reinvestigation
Author(s) -
Deady Leslie W.,
Rodemann Thomas
Publication year - 2001
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.5570380524
Subject(s) - chemistry , reagent , aldehyde , pyridine , quinoline , yield (engineering) , chloride , dimethylformamide , methanol , acetyl chloride , medicinal chemistry , carboxylate , hydrogen chloride , cleavage (geology) , ring (chemistry) , organic chemistry , stereochemistry , catalysis , solvent , materials science , geotechnical engineering , fracture (geology) , engineering , metallurgy
Homophthalic acid and its pyrido and 8‐methylquinolino analogues with dimethylformamide/phosphoryl chloride at 0 ° give the appropriate 4‐(dimethylaminomethylene)isochroman‐1,3‐dione ( 2a, 2b, 2c , respectively). Under the literature conditions for conversion of 2a to 2‐methyl‐1‐oxo‐1,2‐dihydroisoquinoline‐4‐carboxylic acid ( 3a ), the aza analogues give instead 7‐hydroxy‐5‐oxo‐5 H ‐pyrano[4,3‐ b ]pyridine‐8‐carbox‐aldehyde ( 5b ) and 3‐hydroxy‐6‐methyl‐1‐oxo‐1 H ‐pyrano[4,3‐ b ]quinoline‐4‐carboxaldehyde ( 5c ), respectively. Modified conditions were required to isolate analogues 3b and 3c . Further, while reaction of 2a with hydrogen chloride in methanol gave the known change to methyl 1‐oxo‐1 H ‐isochromene‐4‐carboxylate ( 4 ), 2b and 2c gave only products of oxa‐ring cleavage. Methyl 2‐( cis ‐2‐hydroxyvinyl)‐8‐methylquinoline‐3‐carboxylate ( 8 ) was the main product from 2c , while a novel quinolizinium species ( 11 ) was formed in good yield from 2b.