Synthesis and lactim-lactam tautomerism of 1,2-dihydrofuro[2,3-b]quinol-4-one derivatives

Abstract

The reaction of O-ethylbutyrolactonium tetrafluoroborate with derivatives of ethyl anthranilate was used to synthesize tetrafluoroborates of cyclic imido esters, which were cyclized to furo[2,3-b]quinol-4-one derivatives by heating in a solution of sodium ethoxide. A number of N- and O-alkyl derivatives were obtained by alkylation of these compounds. The tautomerism of 6-chloro- and 7-chloro-2,3-dihydrofuro [2,3-b]quinol-4-ones that are unsubstituted in the benzene ring was studied, and a dependence of the position of the tautomeric equilibrium on the solvent and the substituent in the benzene ring was established.