Mediated electrochemical syntheses in conductive microemulsions

Date of Completion

January 1998


Chemistry, Biochemistry|Chemistry, Organic




Microemulsions are attractive as reaction media for electrochemical synthesis owing to their low toxicity and good solubility for species of different polarities. The apparent rates of bimolecular reactions occurred in the interfacial area of bicontinuous microemulsions may be controlled by compositions of microemulsions.^ Intermolecular additions of primary alkyl iodides to 2-cyclohexene-1-one to give 3-alkyl cyclohexanone were mediated by electrogenerated Co(I) form of vitamin B$\sb{12}$. Comparable yields of 3-alkyl cyclohexanone in microemulsions and DMF were achieved. Cyclization of 2-(4-bromobutyl)-2-cyclohexen-1-one to form 1-decalone not only gave 90% of yield but also a high trans/cis ratio (93:7). Mechanistic studies showed that the stereoselective formation of trans isomer of 1-decalone was caused by a keto-enol tautomerization of 1-decalone catalyzed by hydroxide ions which were produced by co-electrolysis of water during the reaction. In an acidic medium, trans and cis isomers were formed in equal amounts.^ A disfavored cyclization of 2-(3-bromopropyl)-2-cyclohexen-1-one to give 4-hydrindanone (70%) was realized under an electrochemical cleavage mode in a bicontinuous microemulsion. This reaction was possibly facilitated by properties of the microemulsion. A 5-exo-trig cyclization in a microemulsion was directed almost exclusively to unsaturated or saturated product by proper control of reaction conditions, which was not achieved in methanol.^ In a separate research project, reductions of the protein myoglobin reconstituted with cobalt(III) heme (MbCo(III)) were accomplished in surfactant films on PG electrodes in buffer. Mediated reduction of oxygen was accomplished with the MbCo(III)/MbCo(II) couple. Electrochemically reversible reduction of MbCo(II) to MbCo(I), the demonstrated reactivity of MbCo(I) with EDB and n-butyl bromide suggest interesting future applications of this reconstituted protein for carbon-carbon bond formation via reactions of alkyl halides with MbCo(I). ^