Intramolecular Biradical Recombination of Dicarboxylic Acids to Unsaturated Compounds: A New Approach to an Old Kolbe Reaction

Abstract

The Kolbe or Non‐Kolbe electrolysis is one of the most studied electro‐organic reactions and a fundamental pillar of organic chemistry. In contrast to classical Kolbe dimerization of monocarboxylic acids, dicarboxylic acids are only scarcely subject for Kolbe electrolysis in the literature despite their vast natural abundance. Herein, we report on the intramolecular biradical recombination of dicarboxylic acids as a green way to prepare alkenes or alkynes over a newly proposed mechanistic route. Proceeding over a radical mechanism without dimerization, it clearly stands out from classical (Non‐)Kolbe electrolysis. In the presence of non‐toxic aqueous solvents, the desired products form in excellent yields (up to 83 %), which are the highest reported for this substrate class. Once feasibility had been shown for the electrolysis of methylsuccinic acid, we could demonstrate its application to a broad scope of different dicarboxylic acids.

Conversion of Polyethylene Waste into Gaseous Hydrocarbons via Integrated Tandem Chemical–Photo/Electrocatalytic Processes

“…This can be explained by the presence of longer chain diacids in the PE solution, which have been shown to be less reactive than succinic acid for the double-decarboxylation reaction. 33 In aqueous solution, acetylene was formed (0.9% Faradaic yield, 1.9 μmol cm cat –2 h –1 ), which was not the case in methanolic solutions ( Table S16 ). The Faradaic yield for H 2 was slightly higher for aqueous and lower for methanolic conditions, compared with the pure succinic acid solution ( Figure 3 , Tables S14 and S16 ).…”

“…Alkaline conditions are beneficial as acid deprotonation facilitates the decarboxylation step ( Figure S11 ), which gives access to a good Faradaic yield for this reaction. 33 Oxygen evolution (determined using a fluorescence oxygen sensor) contributed only approximately 5% to the Faradaic yield. The remaining charge was consumed by the cyclic parasitic nitrate/nitrite redox reaction ( Figure S12 and Table S12 ), which was also responsible for the relatively low Faradaic yield for H 2 evolution at the counter electrode (see the Supporting Information for more details).…”

“…An increased ethylene productivity was observed at higher pH values, giving a Faradaic yield of approximately 30% for carbon paper electrodes at pH 10 (Table S11). Alkaline conditions are beneficial as acid deprotonation facilitates the decarboxylation step (Figure S11), which gives access to a good Faradaic yield for this reaction . Oxygen evolution (determined using a fluorescence oxygen sensor) contributed only approximately 5% to the Faradaic yield.…”

Electrochemical Cleavage of Carbon‐Chlorine Bonds in Multiply Bridge‐Chlorinated Bicyclo[1.1.1]pentane‐1,3‐dicarboxylic Acids

“…Tafel already observed electrochemical reduction of oxalic to glyoxalic acid in 1904. Oxidation of dicarboxylic acids (Kolbe reaction) cannot play role at negative potentials used in this communication [28] …”

3D Printed Microreactors for the Continuous Non‐Kolbe Electrolysis

“…It provides access to nitrogen-or oxygen-functionalized molecules via the reaction with a nucleophile or molecules possessing a terminal double bond formed through deprotonation. These olefins include important monomers like propylene [12,13] or ethyl acrylate [3], whereas oxygenated products show promising applications in fuel design [4] or fine chemical industry [6]. While the general reaction con-ditions of (Non-)Kolbe electrolysis were thoroughly studied [7,8], current research focuses on the substrate scope [14,15], economical and ecologically improved anodes [3,16], and sophisticated reaction engineering like in situ product separation [3,9,10] or continuous processes [10,17,18].…”