Synthesis of Indenoindole Derivatives under Deep Eutectic Solvent Conditions

Abstract

In this study, we synthesized a variety of indole derivatives using commercially available 2,5‐dimethoxybenzaldehyde 18 as a starting material. The synthetic route involves a sequential usage of Knoevenagel and Fischer indolization reactions as key steps and the Fischer indolization is facilitated by deep eutectic solvent (DES) such as L‐tartaric acid/dimethylurea (TA:DMU). All the compounds prepared here are characterized by HRMS, 1H‐NMR and 13C‐NMR data. The methodology described in this study showcases the utility of deep eutectic solvents in facilitating the synthesis of diverse indole derivatives, thereby expanding the toolkit of sustainable synthetic methodologies. These compounds are medicinally important and play a key role as an effective template in Kinase inhibitors (CK2). Various functionalized indeno[1,2‐b]indole scaffolds synthesized here might be valuable as novel inhibitors of human CK2. Elevated levels of protein kinase CK2, previously known as casein kinase 2 or II, have been linked to higher cell growth and proliferation in both normal and cancerous cells.