Synthesis and anti-cancer activity of 1,4-disubstituted imidazo[4,5-c]quinolines

The synthesis and anti-cancer activity evaluation of fused imidazoquinoline compounds is reported in this paper. Yb(OTf)₃ has been utilized as a catalyst for the synthesis of 1,4-diaryl substituted imidazo[4,5-c]quinolines via a modified Pictet–Spengler approach. The desired imidazole ring was synthesized from imines using TosMIC (toluenesulfonylmethyl isocyanide) and subsequently functionalized at the C-4 position yielding an imidazoquinoline skeleton. Importantly, the final step was carried out without the aid of any prefunctionalization to obtain the resultant compounds in good yields. The synthesized compounds, when screened for anti-cancer activity, revealed the highest activity with 4-(2-bromophenyl)-1-phenyl-1H-imidazo[4,5-c]quinoline (IC₅₀: 103.3 μM).