Organocatalytic Asymmetric Cyclization Reactions with γ‐Hydroxyenones

An overview of recent advancements in γ-hydroxyenone-based organocatalytic asymmetric cyclization techniques is given in this review paper. Because γ-hydroxyenones are bifunctional, they are an effective building block for creating oxa-heterocycles.

This review article provides an overview of the recent developments in organocatalytic asymmetric cyclization strategies utilizing γ-hydroxyenones.  Due to the bifunctional nature of γ-hydroxyenones, it is a powerful building block for synthesizing oxygen- and nitrogen-containing heterocycles. The cyclization strategies are systematically categorized based on the nature of the organocatalysts employed: (i) chiral prolinol analogs, which obtain tetrahydrofuran-fused 3,4-dihydrocoumarins and 2,3,4-trisubstituted tetrahydrofurans; (ii) chiral bifunctional squaramides, affording diverse spirocyclic frameworks such as spiro-tetrahydrofuran-pyrazolones, morpholinones, and oxindole-derived systems; (iii) chiral bifunctional thioureas, which forms 1,3-dioxolanes, oxazolidines, and cyclic acetals; (iv) multifunctional modular organocatalysts, affording enantioenriched α,β-disubstituted γ-butyrolactones; and (v) other chiral organocatalysts which cannot be grouped in previous categories such as Song's chiral oligoethylene glycol as a cation-binding catalyst leads to the generation of chiral 1,4,2-dioxazinanes.