Chemistry Reference
In-Depth Information
8.2.3 Paired Electrosynthesis of
Phthalide and
t
-Butylbenzaldehyde
Recently, BASF commercialized the paired
electrosynthesis of phthalide and
t
-butylbenzaldehyde dimethylacetal, as shown
in
Eq. 8.4
[2]. The products are useful as plant
protectors, additives for plating baths,
ultraviolet absorbers, aroma chemicals,
fungicides and so on. Phthalide has been
prepared by classical catalytic hydrogenation of
phthalic acid anhydride, but this method
requires pure hydrogen gas and high pressure.
On the other hand, during anodic
dimethoxylation of
t
-butyltoluene, protons are
predominantly reduced at the cathode to
generate hydrogen gas. BASF made great efforts
to find a compatible reduction process that can
be used instead of proton reduction. Eventually,
the combination of anodic dimethoxylation of
t
-butyltoluene and cathodic reduction of
phthalic acid diester was found to establish the
paired electrosynthesis, as shown in
Eq. 8.4
.
Cathodic reduction of phthalic acid
dimethylester produces phthalide and
methanol, while the resulting methanol is used
for anodic dimethoxylation of
t
-butyltoluene to
provide dimethylacetal in good yield. In this
paired electrosynthesis, the balance of
methanol, proton and electron is remarkable.
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