Organocatalytic Aza-Michael/Mannich Cascade Reaction: Synthesis of Enantioenriched 3,3'-Spirooxindole γ-Lactams
Xiao-Tong Li1, Heng-Zhi Tian1, Xing-Wen Sun1
1Department of Chemistry, Fudan University, Shanghai 200433, China.
Abstract:
Highly enantioselective synthesis of 3,3'-spirooxindole γ-lactams with three contiguous stereocenters (two quaternary) was achieved. The aza-Michael/Mannich cascade reaction of α-imine-β-oxobutanamides and methyleneindolinones catalyzed by a bifunctional diaminocyclohexane-derived thiourea catalyst gave the desired products in moderate to good yields (up to 78%), moderate to good diastereoselectivities (up to 10:1 dr), and good to excellent enantioselectivities (up to >99% ee). A gram-scale synthesis and some transformations of 3,3'-spirooxindole γ-lactams were also carried out.
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