Quinoli necarboxylates

The thermal ring closure of AKl,3-benzodithiol-5-yl)aminomethylene-malonate (860) in Dowtherm A at 253-258°C led to a 7.3 1 mixture of 1,3-dithiolo[4,5-g]quinolinecarboxylate (861) and l,3-dithiolo[4,5-/]quinoli-necarboxylate (862) in 81% yield (86M1339). The cyclization of diethyl N-(3,4-dimethylthiophenyl)aminomethylenemalonate under similar conditions afforded only ethyl 6,7-dimethylthio-4-hydroxyquinoline-3-carbox-ylate. 

Diethyl aryl(chloro)methylenemalonates (1670) were reacted with aniline in the presence of triethylamine at 90°C for 12 hr to give aryl(phenyl-amino)methylenemalonates (1671) in 57-66% yields (90JOC2513). The thermal cyclization of compound 1671 (Ar = 3-furyl) at 250°C gave quinoli-necarboxylate (1672) in 85% yield. The cyclizations of compounds 1671 (Pr = Ph, 3-thienyl) in polyphosphoric acid at 210-230°C for 5 min afforded tetracyclic derivatives (1673) in 50-75% yields. 

A general method for the preparation of 2-hydroxymethyl-3-quinoli-necarboxylic acid lactones 8 (70-100%) from an o-amino aromatic carbonyl compound uses tetronic acid 7 (Scheme 4) (58JOC1996). 

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