Functionally Substituted Quinaldic Acid Esters

Steglich reaction of hydroxybenzaldehydes with quinaldic acid resulted in the formation the corresponding esters. Their condensation with 4-aminophenol and 2-naphthylamine gave (E)-azomethines. The latter were subsequently acylated with 4,5-dichloroisothiazole-3-carbonyl chloride in the presence of triethylamine to form products containing quinoline and isothiazole moieties. Condensation of these compounds with dimedone in butanol afforded benzacridines. The latter were also obtained by a cascade three-component condensation of the aldehydes with dimedone and 2-naphthylamine in butanol in higher yields.