Selective Electrosynthetic Hydrocarboxylation of α,ß-Unsaturated Esters with Carbon Dioxide*.

The carboxylation of low-value commodity chemicals to provide higher-value carboxylic acids is of significant interest. Recently alternative routes to the traditional hydroformylation processes that used potentially toxic carbon monoxide and a transition metal catalyst have appeared. A significant challenge has been the selectivity observed for olefin carboxylation. Photochemical methods have shown a viable route towards the hydrocarboxylation of α,ß-unsaturated alkenes but rely on the use of an excess reducing or amine reagent. Herein we report our investigations of an electrochemical approach that is able to hydrocarboxylate α,ß-unsaturated alkenes with excellent regioselectivity and the ability to carboxylate hindered substrates to afford α-quaternary center carboxylic acids. The reported process requires no chromatography and the products are purified by simple crystallization from the reaction mixture after work-up.

Selective α,δ-hydrocarboxylation of conjugated dienes utilizing CO2 and electrosynthesis.

To date the majority of diene carboxylation processes afford the α,δ-dicarboxylated product, the selective mono-carboxylation of dienes is a significant challenge and the major product reported under transition metal catalysis arises from carboxylation at the α-carbon. Herein we report a new electrosynthetic approach, that does not rely on a sacrificial electrode, the reported method allows unprecedented direct access to carboxylic acids derived from dienes at the δ-position. In addition, the α,δ-dicarboxylic acid or the α,δ-reduced alkene can be easily accessed by simple modification of the reaction conditions.