Methods for Organic Electrosynthesis - Fundamentals and Applications of Organic Electrochemistry - page 63

However, such polarity inversion (umpolung)
can be readily achieved in one step by cathodic
reduction of the alkyl halides, as shown in Eq.
4.1 . When the basic products are isolated after
Grignard reaction, the work up can be
troublesome, and it may be rather difficult to
separate the product from aqueous alkaline
solution due to insoluble Mg(OH) 2 . In sharp
contrast, in the case of electrolytic reactions,
the product isolation is rather easy and the
severe waste problem does not occur because
there is no use of metals. In addition,
electrolytic reactions do not require easily
flammable ethereal solvents, and alternative
solvents like acetonitrile can be used as
electrolytic solvents.
(4.1)
When alkyl substituents are introduced to
phosphine, silicon and stannum compounds,
their corresponding chloro compounds (R 3 ZCl,
R 2 PCl) and alkyl Grignard reagents are usually
used. However, electrochemical reduction of
these chloro compounds generates the anionic
intermediates, which can readily react with
alkyl halides (R′X) to provide the
corresponding alkyl-substituted products ( Eq.
4.2 ).
(4.2)