Enantioselective Protonation of Cyclic Carbonyl Ylides by Chiral Lewis Acid Assisted Alcohols

Abstract

Chiral Lewis acid-catalyzed asymmetric alcohol addition reactions to cyclic carbonyl ylides generated from N-(α-diazocarbonyl)-2-oxazolidinones featuring a dual catalytic system are reported. Construction of a chiral quaternary heteroatom-substituted carbon center was accomplished in which the unique heterobicycles were obtained in good yields with high stereoselection. The alcohol adducts were successfully converted to optically active oxazolidine-2,4-diones by hydrolysis. Mechanistic studies by DFT calculations revealed that alcohols could be activated by Lewis acids, enabling enantioselective protonation of the carbonyl ylides.

Catalytic asymmetric [3+2] cycloaddition of isomünchnones with methyleneindolinones

“…Suga used achiral Rh( ii ) and chiral Ph-Pybox/Ln( iii ) as the bimetallic relay catalytic cycloaddition of six-membered cyclic carbonyl ylides with benzyloxyacetaldehydes, vinyl ethers and electron-deficient olefins, as well as the reaction of isomünchnones with oxazolidinones. 9 Our group used achiral Rh( ii ) and chiral N , N ′ -dioxides/Zn( ii ) as the bimetallic relay catalyst to accomplish the highly efficient [4+3] cycloaddition of β,γ-unsaturated α-ketoesters with isomünchnones to yield oxa-bridged oxazocines. 10…”