Stereoselective Access to β‐gem‐Difluorinated Alcohols Through Enzymatic Reduction

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We report here a mild process to access diversely functionalized enantioenriched β‐ gem ‐difluorinated ( S )‐alcohols by using biocatalytic reduction in >99% yield and enantiomeric excesses ranging from 96% to >99%. This novel approach involves enzymatic reduction of α‐ gem ‐difluorinated heterocyclic and carbocyclic ketone derivatives as well as an acyclic gem ‐difluorinated β‐ketosulfone and proceeds under mild conditions at 30 °C under aqueous conditions to produce a range of high added value enantioenriched difluorinated alcohols including 3,3‐difluorochromanol, 3,3‐difluorothiochromanol, 3,3‐difluoro‐dihydroquinolinol, and α‐difluorinated β‐hydroxysulfone derivatives. A comparative study between enzymatic reduction and metal‐catalyzed asymmetric transfer hydrogenation was carried out as well.