Constant current electrolysis of 2-(2-propynyloxy)bromobenzenes in DMF using an undivided cell equipped with a Pt cathode and an Mg anode in the presence of carbon dioxide and an electron transfer mediator, methyl 4-tert-butylbenzoate, resulted in aryl radical cyclization with a carbon–carbon triple bond followed by fixation of two molecules of carbon dioxide to give 2,2-ring-fused succinic acid derivatives in moderate to good yields. Dihydrobenzofuran, indoline, dihydrobenzothiophene, and indane as well as tetrahydropyran skeletons were successfully constructed by aryl radical cyclization, and unique tandem carboxylation successively occurred to produce succinic acids. One of the resulting succinic acid derivatives, 3-carboxy-2,3-dihydrobenzofuran-3-ylacetic acid, was successfully applied to the synthesis of a novel spiro compound consisting of 2,3-dihydrobenzofuran and γ-butyrolactone at each C3 position in two steps in high yield.

Electrochemical direct carboxylation of benzyl alcohols having an electron-withdrawing group on the phenyl ring was successfully carried out by constant current electrolysis using an undivided cell equipped with a platinum plate cathode and a magnesium rod anode in DMF in the presence of carbon dioxide. Reductive cleavage of the C–O bond followed by fixation of carbon dioxide efficiently took place at the benzylic position without any additive to give the corresponding phenylacetic acids in good yields in one step under neutral and mild conditions.

Sacrificial anode-free efficient electrochemical carboxylation of benzylic halides was successfully performed by using a paired electrolysis protocol. Constant-current electrolysis of a DMF solution of benzylic halides in the presence of carbon dioxide using a one-compartment cell equipped with a Pt plate cathode and a Pt wire anode (quasi-divided cell) resulted in efficient three-component coupling reaction of benzylic halides, carbon dioxide and DMF to yield N-methyl-N-(phenylacetoxy)methylformamides, as carboxylated coupling products, in good yields.

Hg cathode-free electrochemical detosylation of N,N-disubstituted p-toluenesulfonamides was successfully carried out by a constant current electrolysis using an undivided cell equipped with a platinum cathode and a magnesium anode in the presence of an arene mediator. The deprotection proceeded efficiently and selectively under neutral and mild conditions with a stoichiometric amount of electricity without the use of an Hg cathode to obtain the corresponding secondary amines in good to excellent yields.

•Studies carried out in the past two years on electrochemical carboxylation.•Recent results on Asymmetric Electrochemical Carboxylation.•Use of Ionic Liquids in Electrochemical Carboxylation.•Recent developments in Sacrificial Anode-free Electrochemical Carboxylation.•Tandem Carboxylation following Aryl Radical Cyclization to Alkynes.Studies carried out in the past two years on electrochemical fixation of carbon dioxide with carbon-carbon bond formation, so-called electrochemical carboxylation or electrocarboxylation, are reviewed. Among about twenty papers on electrochemical carboxylation published from 2014 to the present, recent advances in electrochemical carboxylation regarding asymmetric carboxylation, sacrificial anode-free carboxylation, and carboxylation following aryl radical cyclization are focused on and discussed.Download high-res image (209KB)Download full-size image