An efficient, metal free and environment friendly synthesis of isoquinoline-fused benzimidazole has been developed via in situ air oxidation. Also, syntheses of isoquinoline-fused quinazolinone heteroacenes were successfully achieved. The synthesized isoquinoline-fused benzimidazole and isoquinoline-fused quinazolinone derivatives showed λ_max, F_max and Φ_f values in the ranges 356–394 nm, 403–444 nm and 0.063–0.471, respectively, in CHCl₃.