Enantioselective Synthesis of 3‐Acetyl Coumarin Substituted 3‐Hydroxy Oxindoles and Pyranocoumarin Fused Spirooxindoles

Abstract

AbstractEnantioselective construction of bioinspired coumarin and oxindole hybrid structures always enduring challenges in organic chemistry due to the generation of asymmetric quaternary/spiro center at the C3 position of oxindole. Herein, we demonstrated a facile enantioselective synthesis of highly functionalized 3,3’‐disubstituted oxindole derivatives containing 3‐acetyl coumarins and pyranocoumarin fused spirooxindoles using L‐proline derived bifunctional thiourea organocatalyst through Aldol reaction and Michael addition/cyclization. The L‐proline derived thiourea catalyst well performed with broad substrate scope to produce desired products in very good yields (up to 95 %) and excellent enantioselectivities (up to 99 % ee).