Bifunctional phosphonium/thioureas derived from tert-leucine behaved as highly selective catalysts for enantioselective protonation of enol esters, providing α-chiral ketones in yields of up to 99% with high enantioselectivities (up to 98.5:1.5 er). Control experiments clarified that a bulky tert-butyl group and phosphonium and thiourea moieties were necessary to achieve such high stereoselectivity
Like an enzyme: Asymmetric hydrolysis of enolesters is accomplished by chiral phase‐transfer catalysts under biphasic base hydrolysis conditions. Stoichiometric reactions support the generation of a well‐organized chiral ammonium hydroxide species (Q+OH−).