Electrochemical synthesis of carboxylic acids from alkenes using various nickel-organic mediators:: CO2 as C1-synthon

Direct and mediated electrochemical reductive coupling reactions between alkenes and CO2 have been studied using an undivided electrochemical cell. Propene and 1-butene were used to study the behavior of monoenes. Propene, in the absence of a mediator, yielded two main products: 2-methyl-butanedioic acid and 3-butenoic acid; from 1-butene, mainly ethenylsuccinic acid and 3-pentenoic acid were generated. As a conjugated diene, 1,3-butadiene was investigated intensively. In the absence of a mediator, 1,3-butadiene was mainly dicarboxylated to give the 1,2- (2-ethenyl-succinic acid) and 1,4-addition product (3-hexene-1,6-dioic acid) and various higher coupling products. Using an NiN3 mediator the reaction between 1,3-butadiene and CO2 resulted in a preferred generation of the 1,4-addition product: 3-hexene-1,6-dioic acid. Experiments with a Ni(cyclam) mediator resulted in an increased concomitant generation of a monocarboxylation product: 3-pentenoic acid. Copyright (C) 2001 John Wiley & Sons, Ltd.