Enantioselective Epoxidation of Electrophilic Olefins by Using Glycosyl Hydroperoxides

Abstract

Anomeric hydroperoxides derived from 3,4,6-tri-O-benzyl-galactose and glucose were used for enantioselective epoxidation of naphthoquinone (12), chalcone (13), (E)-1,2-dibenzoyl ethylene (14) and (E)-iso-butyryl-phenyl ethylene (15). In the presence of sodium hydroxide, the epoxidations showed exceptional high asymmetric induction. The exchange of sodium by a potassium ion resulted in a low asymmetric induction. These results pointed to the crucial role of the counterion and strongly suggested that coordination of the alkaline ion occurs in the transition state of the epoxidation process by both reagents, hydroperoxide and the olefin. Theoretical studies of the reaction mechanism at the DFT B3LYP/6-31G* level fitted very well with experimental results.

Menadione: a platform and a target to valuable compounds synthesis

“…The authors studied a broad range of quinone derivatives among which compound 39 was obtained through reaction of menadione ( 10 ) and hydroperoxide 38 in 71% yield and 45% ee ( Scheme 11A ). Analogously, Kosnik and co-workers described a similar epoxidation methodology using a series of pyranose-derived anomeric hydroperoxides (HPO) to obtain epoxides 40 with moderate ees ( Scheme 11B ) [ 100 – 101 ]. Bunge and co-workers used the enantiomerically pure dihydroperoxide 41 in the DBU-mediated epoxidation of menadione ( 10 ) for the enantioselective synthesis of epoxide 42 (92% yield and 45–66% ee) ( Scheme 11C ) [ 102 ].…”

Facile Epoxidation of α,β-Unsaturated Ketones with trans-3,5-Dihydroperoxy-3,5-dimethyl-1,2-dioxolane as an Efficient Oxidant

“…[12][13][14][15][16][17][18][19] Anomeric hydroperoxides derived from 3,4,6-tri-O-benzyl-galactose and glucose were used for enantioselective epoxidation of naphthoquinone, chalcones, (E)-1,2-dibenzoyl ethylene, and (E)-iso-butyrylphenyl ethylene. 20 Most recently, we reported a novel use of trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane in selective sulfoxidation of sulfides. 21 In the last few years, great attention has been paid to epoxidation of a,b-unsaturated ketones due to the important role of epoxides, 22,23 especially chiral epoxides, as useful building blocks in organic synthesis, for example, in the synthesis of pharmaceutical and natural products.…”