Organic Electrode Reactions - Fundamentals and Applications of Organic Electrochemistry - page 139

not useful. Here, methods (iv)-(vi) are
explained.
In 1967, Grimshaw first reported the
asymmetric reduction of 4-methylcumarine
using optically active alkaloids, and a maximum
asymmetric yield (17%) was obtained using a
small amount of sparteine (1 mM) as a chiral
electrode adsorbant [35]. After 10 years, Miller
obtained 48% asymmetric yield in the cathodic
reduction of 2-acethylpyridine to the
corresponding alcohol in the presence of 0.5
mM of strychnine salt [36]. Asymmetric
induction seems to be attributable to the chiral
reaction fields constructed by the physical
adsorption of optically active alkaloids on the
cathode surface. However, such asymmetric
electrosynthesis is very sensitive to electrolytic
conditions such as stirring, concentration,
solvent, cathode potential and so on.
Miller and co-workers found that prochiral
carbonyl compounds like ethyl phenylglyoxylate
were reduced to chiral alcohols in 10%
asymmetric yield on a cathode chemically
modified with ( S )-phenylglycine [37]. They also
reported asymmetric oxidation of p -tolyl
methyl sulfide to the sulfone with 2.5% ee by
using a similar electrode modified with
(+)-camphoric acid [38]. These are also
pioneering works on chemically modified
electrodes. The low asymmetric yields seem to
be due to a low density of chiral compound on