Enantioselective Construction of Chiral Cyclopropa[<i>c</i>]coumarins via Lewis Base-Catalyzed Cyclopropanation
Jun‐Chao Sun, Xiaohui Wang, Cong‐Bin Ji, Yiyuan Peng, Xing‐Ping Zeng
Abstract
The first highly enantioselective construction of chiral cyclopropa[c]coumarins was described. Using commercially available (bis)cinchona alkaloid (DHQ)2PYR as the chiral Lewis base catalyst, together with Cs2CO3 as the achiral base, the reaction of a series of coumarin-3-carboxylate and 3-benzoyl coumarins with tert-butyl 2-bromoacetate could give rise to the corresponding cyclopropa[c]coumarins bearing three continuous chiral stereocenters in 83–93% ee and 90–97% ee, respectively. The reaction is proposed to proceed via an in situ generated ammonium ylide intermediate.
Topics & Concepts
CyclopropanationEnantioselective synthesisCatalysisLewis acids and basesBase (topology)ChemistryOrganic chemistryStereochemistryMathematicsMathematical analysisCyclopropane Reaction MechanismsAsymmetric Synthesis and CatalysisCatalytic C–H Functionalization Methods