Organocatalytic Sequential α-Amination/Corey–Chaykovsky Reaction of Aldehydes: A High Yield Synthesis of 4-Hydroxypyrazolidine Derivatives

A tandem reaction of <i>in situ</i> generated α-amino aldehydes with dimethyloxosulfonium methylide under Corey–Chaykovsky reaction conditions proceeds efficiently to give 4-hydroxypyrazolidine derivatives in high yields with excellent enantio- and diastereoselectivities. This organocatalytic sequential method provides for the efficient synthesis of <i>anti-</i>1,2-aminoalcohols, structural subunits present in several bioactive molecules as well

Proline-Catalyzed Sequential <i>syn</i>-Mannich and [4 + 1]-Annulation Cascade Reactions To Form Densely Functionalized Pyrrolidines

A highly efficient one-pot [4 + 1]-annulation process for the asymmetric synthesis of densely functionalized pyrrolidine derivatives is described. The in situ generated <i>syn</i>-Mannich adduct obtained via proline catalysis acts as a four-atom component, and Corey’s sulfur ylide or ethyl bromoacetate acts as a one-atom carbon source to construct pyrrolidine units in a highly enantio- and diastereoselective manner

Fluoride Anions in Self-Assembled Chiral Cage for the Enantioselective Protonation of Silyl Enol Ethers

The potential of Song’s chiral oligoethylene glycols (oligoEGs) as catalysts was explored in the enantioselective protonation of trimethylsilyl enol ethers in combination with alkali metal fluoride (KF and CsF) and in the presence of a proton source. Highly enantioselective protonations of various silyl enol ethers of α-substituted tetralones were achieved, producing chiral α-substituted tetralones in full conversion and with up to 99% ee. The established protocol was successfully extended to the synthesis of biologically relevant chiral α-substituted chromanone and thiochromanone derivatives