A strategy of visible light‐induced salan‐copper(II)‐catalyzed asymmetric α‐hydroxylation of β‐keto ester with utilization of sustainable air as the oxidant was developed. This protocol allows convenient access to a number of enantioenriched α‐hydroxyl β‐keto esters (up to 95% yield, 96% ee), especially for β‐keto methyl esters that are valuable architectures in pharmaceuticals, including the key intermediate
A novel library of chiral guanidines featuring a tartaric acid skeleton was developed from diethyl L-tartrate. These guanidines are easily accessed with tunable style and electronic properties. The utilities of the guanidines were highlighted by their ability to catalyze the alpha-hydroxylation of beta-ketoesters and beta-diketones with remarkable efficiency and excellent enantioselectivity.