Friedländer reaction/quinoxalinone–benzimidazole rearrangement sequence: expeditious entry to diverse quinoline derivatives with the benzimidazole moieties

Abstract

A protocol has been developed for the efficient synthesis of structurally diverse 4-(benzimidazol-2-yl)quinolines via reactions of 3-(2-aminophenyl)quinoxalin-2(1H)-ones and ketones, including acetone, acetophenones, 1,3-pentanedione and ethyl acetoacetate. The selective formation of the very different quinoline derivatives depends on the structure of ketones. The key steps are proposed to involve the new acid-catalyzed rearrangement of the spiro-quinoxalinone derivatives formed in situ from the reaction of 3-(2-aminophenyl)quinoxalin-2(1H)-ones and ketones under the modified Friedländer reaction. This transformation would facilitate the synthesis by short reaction times, large-scale synthesis, simple and prompt isolation of the products, which are the main advantages of this procedure.