Nonheme Iron-Catalyzed Enantioselective cis-Dihydroxylation of Aliphatic Acrylates as Mimics of Rieske Dioxygenases

Abstract

Enantioselective cis-dihydroxylation of alkenes represents an ideal route to synthesize enantioenriched syn-2,3-dihydroxy esters that are important structural motifs in numerous biologically and pharmaceutically relevant molecules. Bioinspired nonheme iron-catalyzed enantioselective cis-dihydroxylation meets the requirement of the modern synthetic chemistry from the atomic economy, green chemistry, and sustainable development perspectives. However, nonheme iron-catalyzed enantioselective cis-dihydroxylation is much underdeveloped because of the formidable challenges of controlling chemo- and enantioselectivities and product selectivity caused by the competitive epoxidation, cis-dihydroxylation, and overoxidation reactions. Herein, we disclose the fabrication of a biologically inspired nonheme iron complex-catalyzed enantioselective cis-dihydroxylation of multisubstituted acrylates using hydrogen peroxide (H2O2) as the terminal oxidant by controlling the non-ligating or weakly ligating counterions of iron(II) complexes, demonstrating a dramatic counteranion effect on the enantioselective cis-dihydroxylation of olefins by H2O2 catalyzed by nonheme iron complexes. A range of structurally disparate alkenes were transformed to the corresponding syn-2,3-dihydroxy esters in practically useful yields with exquisite chemo- and enantioselectivities (up to 99% ee). Given the mild and benign nature of this biologically inspired oxidation system as well as the ubiquity and synthetic utility of enantioenriched syn-2,3-dihydroxy esters as pharmaceuticals candidates and natural products, we expect that this strategy could serve as a promising complement to the well-known Sharpless asymmetric dihydroxylation, which is the chemical reaction of an alkene with OsO4 to produce a vicinal diol.