Asymmetric Direct α‐Hydroxylation of β‐Oxo Esters by Phase‐Transfer Catalysis Using Chiral Quaternary Ammonium Salts

Abstract The first enantioselective direct α‐hydroxylation of β‐oxo esters was developed by using phase‐transfer catalysis. 1‐Indanone‐derived 1‐adamantyl (1‐Ad) β‐oxo esters, in the presence of commercially available cumyl hydroperoxide and a cinchonine‐based ammonium salt, resulted in the corresponding products with 69–91 % yield and 65–74 % ee . The reaction had also been successfully scaled‐up to a gram quantity, and a similar yield was obtained without loss of the enantioselectivity.