The reaction of homophthalic acid and some aza analogues with Vilsmeier reagent: a reinvestigation

Citation
Lw. Deady et T. Rodemann, The reaction of homophthalic acid and some aza analogues with Vilsmeier reagent: a reinvestigation, J HETERO CH, 38(5), 2001, pp. 1185-1190
Citations number
7
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
JOURNAL OF HETEROCYCLIC CHEMISTRY
ISSN journal
0022-152X → ACNP
Volume
38
Issue
5
Year of publication
2001
Pages
1185 - 1190
Database
ISI
SICI code
0022-152X(200109/10)38:5<1185:TROHAA>2.0.ZU;2-7
Abstract
Homophthalic acid and its pyrido and 8-methylquinolino analogues with dimet hylformamide/phosphoryl chloride at 0 degrees give the appropriate 4-(dimet hylaminomethylene)isochroman-1,3-dione (2a, 2b, 2c, respectively). Under th e literature conditions for conversion of 2a to 2-methyl-1-oxo-1,2-dihydroi soquinoline-4-carboxylic acid (3a), the aza analogues give instead 7-hydrox y-5-oxo-5H-pyrano[4,3-b]pyridine-8-carboxaldehyde (5b) and 3-hydroxy-6-meth yl-1-oxo-1H-pyrano[4,3-b]quinoline-4-carboxaldehyde (5c), respectively. Mod ified conditions were required to isolate analogues 3b and 3c. Further, whi le reaction of 2a with hydrogen chloride in methanol gave the known change to methyl 1-oxo-1H-isochromene-4-carboxylate (4), 2b and 2c gave only produ cts 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.