Synthesis of [1,3,4]Thiadiazolo[3′,2′:1,2]imidazo[4,5-c]quinolines including Pictet–Spengler Reaction and Exploration of Their C-2 Reactivity through SNAr

This work reports the design of [1,3,4]thiadiazolo[3′,2′:1,2]imidazo[4,5-c]quinolines using a Pictet–Spengler reaction. The scope of the reaction was achieved from 6-(2-aminophenyl)imidazo[2,1-b][1,3,4]thiadiazole derivatives and available aldehydes. A wide range of aldehydes were employed to examine the scope of the cyclization. In parallel, a mechanism investigation was realized and showed a hydride transfer which led to a dismutation of the intermediate species. To complete this methodological study, a “sequential” oxidation/SNAr procedure was performed to achieve C-2 nucleophilic substitution using several amine types.