Reactions of N-hydroxysuccinimide esters of anthranilic acids with anions of beta-keto esters. A new route to 4-oxo-3-quinolinecarboxylic acid derivatives.

A new approach for the synthesis of 4-oxo-3-quinolinecarboxylic acid derivatives is described. This methodology involves the C-acylation of the anions of appropriate beta-keto esters with novel N-hydroxysuccinimide esters of anthranilic acids. The intermediate C-acylation products 3 are spontaneously cyclized to afford 3-ethoxycarbonyl-4-oxoquinoline derivatives 4. The introduction of a variety of substituents at positions 1 and 2 of the quinoline ring is feasible with the selection of suitable anthranilic acids and beta-keto esters. The structure of the obtained 2-substituted 3-ethoxycarbonyl-4-oxoquinolines was confirmed by IR and NMR spectral data.