Enantiomerically enriched amines with a stereogenic center at the position adjacent to the primary amino group represent an important class of compounds. They serve as building blocks in the synthesis of drug molecules, as auxiliaries, and as ligands for homogeneous catalysis. Menthylamines are an underused class of chiral amines due to their poor availability.
Siegfried Waldvogel and co-workers, Bonn University, Germany, have reported an electrochemical synthesis of menthylamines in which the choice of cathodic material determines which epimer of menthylamine is formed. The reduction of menthone oxime on a Hg cathode generated (–)-menthylamine, while formation of (+)-neomenthylamine required a Pb cathode. Addition of quaternary ammonium salts allowed quantitative conversion and prevented corrosion of the Pb cathode.
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- Efficient and Stereodivergent Electrochemical Synthesis of Optically Pure Menthylamines
J. Kulisch, M. Nieger, F. Stecker, A. Fischer, S. R. Waldvogel,
Angew. Chem. Int. Ed. 2011.