Enantioselective Organocatalytic Epoxidation Driven by Electrochemically Generated Percarbonate and Persulfate

Abstract

An organocatalytic asymmetric epoxidation reaction using iminium salt catalysts is described, in which the stoichiometric persulfate oxidant is generated electrochemically. This system offers comparable ees to the use of commercially available persulfate. Electrochemically generated percarbonate ion is also a successful and novel oxidant system for use with iminium salts

Green Organocatalytic Oxidative Methods using Activated Ketones

“…[32] Along the lines of oxaziridines, Bulman Page and co-workers have spent most of their research in the epoxidation of alkenes by using iminium salts such as 13 and 14 ( Figure 1). [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] More recently,i n2 013, Bulman Page managed to extend the use of catalyst 15 in heterogeneousc atalysis, while showing the first resultso fk inetic resolution in the epoxidation reaction by employing iminium salt catalysis,b yw hich enantiomeric excess values of up to 99 %f or the epoxidation of racemic cischromenes could be achieved (Scheme 11). Furthermore, a new familyo fc arbohydrate-based dihydroisoquinolinium salts 14 and 16 has been reported,a nd most recently,B ulman Page and co-workersh ave developed the first examples of the asymmetrice poxidation of dihydroquinoline substrates with iminium salt catalysts (Scheme 12).…”

Electrosynthesis of cyclic carbonates from epoxides and atmospheric pressure carbon dioxide

“…Currently the only successful system is that reported by North and co-workers which employs a bimetallic salen complex such as 3 ( Figure 1) and tetrabutylammonium bromide as a co-catalyst, 12 although later 60 developments have incorporated the co-catalyst into the salen substructure. We were interested in developing a low energy alternative in line 65 with our current research portfolio aimed at electrosynthesis 13 coupled with semiconductor photoelectrodes to drive light assisted electrosynthetic reactions. 14 We were therefore attracted to the possibility of employing an electrosynthetic system as this type of process could be designed to be cost neutral in terms of energy consumption if combined with a suitable solar powered energy source.…”

Elektrifizierung der organischen Synthese

“…Further work was done on electrochemical epoxidations.Page,Marken, and co-workers used electrochemically generated peroxodicarbonate and peroxodisulfate for the epoxidation of an iminium catalyst. [142] Thee nantiomeric excess was generally higher when persulfates were employed. Styrene-type alkenes were successfully converted, and boron-doped diamond was crucial for the generation of the peroxo species.H igh current densities were applied, and the electrolysis step was performed prior to catalyst addition.…”

“…Percarbonate-or persulfate-mediated epoxidation. [141,142] Scheme 50. Hypobromide-mediated epoxidation for the synthesis of indinavir.…”