(Diacyloxyiodo)arenes as Versatile Reagents for the Asymmetric α-Acyloxylation of Aldehydes via Enamine Catalysis.

Enantioselective α-acyloxylation of aldehydes was successfully developed using hypervalent iodine(III) reagents in enamine catalysis. Investigation of various oxidants revealed that 2,6-dichloro(diacetoxyiodo)benzene serves as a highly efficient electrophile for the α-acetoxylation. When combined with a chiral tritylpyrrolidine catalyst, this protocol afforded the desired products with excellent enantioselectivity (up to >99% ee). A significant advantage of this method is its high versatility; various acyloxy groups can be introduced either by employing specific (diacyloxyiodo)arenes or through the in situ ligand exchange of the 2,6-dichloro reagent with the corresponding carboxylic acids.