Reductive Coupling of Isatins with α,β-Unsaturated Carbonyl Compounds by Low-Valent Titanium

Abstract

Abstract The reductive coupling of isatins with α,β-unsaturated carbonyl compounds by Zn-TiCl4 in THF at 0 °C gave one-to-one coupled products, 3-hydoxy-3-alkyloxindoles. The coupled products obtained from α,β-unsaturated esters were transformed to the corresponding spiro-γ-lactones by refluxing in cat. PPTS/benzene. The two-to-one coupled products, 3,3-bis(2-carbomethoxyethyl)oxindoles, were formed by the reduction of isatins with methyl acrylate by Zn-TiCl4 in THF at 30 °C. The one-to-one coupled products obtained from the reductive coupling of isatins with methyl acrylate were reduced to 3-(2-carbomethoxyethyl)oxindoles by Zn-TiCl4 in THF at 30 °C. The 3-(2-carbomethoxyethyl)oxindoles added to acrylonitrile to give 3-(2-carbomethoxyethyl)-3-(2-cyanoethyl)oxindoles.