Substitution of Hydroxyl Groups by Deuterium in the Electrochemical Reduction of Methanesulfonates

Abstract

The electrochemical reduction of dodecyl methanesulfonate (ROMs; R = n-C₁₂H₂₅ ⁻, Ms = CH₃SO₂ ⁻) as model compound was studied in deuterated media. This reaction could be of potential use in syntheses of partially deuterated compounds by conversion of C‒OH-groups into C‒D-bonds in the presence of other reactive groups. In order to obtain detailed information about the origin of the introduced hydrogen all individual components (solvent, supporting electrolyte, substrate) of the reaction system were deuterium labelled in the model reaction. The experiments indicate, that this reduction does not proceed along a uniform pathway. Dodecyl anions play the dominating role in the reaction mechanism. Deuterium is transferred into the product dodecane-d ₁ from all components of the reaction mixture in the order of their relative proton acidities Ms-d ₃ > Bu₄N⁺-d ₃₆ > DMF-d ₇ > R-1,1-d ₂-OMs.

In the presence of D²O a hydrogen isotope exchange was found with the methyl group of MsO⁻, catalyzed by electrogenerated bases.

Key Words:

• Deuterium
• dimethylformamide
• dodecane
• dodecyl methanesulfonate
• electrochemical reduction
• isotope exchange
• NMR
• reaction mechanism
• tetrabutylammonium tosylate