Methods for Organic Electrosynthesis - Fundamentals and Applications of Organic Electrochemistry - page 72

stereocontrol. In the cases of cathodic
hydrogenation and anodic addition of cyclic
olefins, cis -form products are preferentially
formed. This is also attributable to addition of
protons and nucleophiles to the anionic and
cationic intermediates adsorbed on the
electrode, respectively.
(b) Stereoselectivity Controlled by Steric
Hindrance between Substrate and Electrode
Simple stereocontrol is achieved by steric
hindrance between substrate and electrode. As
we can easily see in Figure 4.7 , the orientation
of bicyclic gem -dibromocyclopropane at the
cathode surface as shown in (a) is favoured over
that of the substrate shown in (b) owing to
steric repulsion between the cathode and the 6-
or 8-membered ring fused to cyclopropane.
Therefore, the exo -bromide near the cathode is
more easily reducible than the endo -bromide,
and consequently the endo -bromide product is
mainly formed [15].