Diastereoselective Three-Component 1,3-Dipolar Cycloaddition: Concise Synthesis of Functionalized Tetrahydrocarboline-fused Spirooxindoles

A novel diastereoselective and regioselective three-component 1,3-dipolar cycloaddition for the concise synthesis of functionalized tetrahydrocarboline-containing spirooxindoles is reported. Diverse 5-(2-nitroaryl)-2,4-dienones were ingeniously employed as dipolarophiles in 1,3-dipolar cycloaddition, affording two types of isomerized tetrahydrocarboline-fused spirooxindoles in 61-93% yields with excellent diastereoselectivities (up to >99 : 1 dr). This reaction not only expands the scope of dipolarophiles in 1,3-dipolar cycloadditions but also enhances the structural and functional diversity of spirooxindoles.