Studies towards a new C-alkylation method at 3-position of indoles

We report a new facile synthesis procedure for the C-alkylation reaction of indole and indole derivative at 3-position with cyclic enol ethers in the presence of 2.5 mol% of I₂ under mild conditions. The optimum composition of the reaction mixture and catalyst were determined for maximum yield of C-alkylated indole derivative with molar ratio of indole derivative: cyclic enol ether was fixed at 1.0 equivalence: 1.5 equivalence with the presence of 2.5 mol% of I₂ in acetonitrile solvent and room temperature conditions. The results showed that under optimum conditions indole derivatives can be obtained good to excellent yields (80–92%) by the C-alkylation of indoles with cyclic enol ethers. Graphic abstract: