Scope and mechanism of the electrochemical Reformatsky reaction of α-haloesters on a graphite powder cathode in aqueous anolyte

• >Six α-haloesters and eighteen carbonyl compounds were reduced on a graphite powder cathode using aqueous electrolyte free of organic solvents.>Preparative yields of coupling products could be obtained with ethyl 2-bromoisobutyrate and aromatic aldehydes.Ethyl 2-bromopropionate was much less efficient.>Extensive variation of applied potential, electrolyte composition, stoichiometry, catalyst, leaving halogen and activating substituents on the carbonyl compound were tested.>Ethyl chloroacetate produced only trace amounts of coupling product.

Six α-haloesters and eighteen carbonyl compounds were submitted to electrochemical coupling on a graphite powder cathode using aqueous anolyte free of organic solvents. Preparative yields of coupling products could be obtained with ethyl 2-bromoisobutyrate and aromatic aldehydes. Ethyl 2-bromopropionate was much less efficient. Extensive variation of applied potential, electrolyte composition, stoichiometry, catalyst, leaving halogen and activating substituents on the carbonyl compound led to the conclusion that the reaction mechanism in most cases proceeds via a radical intermediate generated from the halide reduction. Ethyl chloroacetate produced only trace amounts of coupling product, most probably by a carbanionic mechanism.

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