Communication
ChemComm
Notes and references
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Scheme 5 Proposed mechanism between 1a and 2a.
anion, to generate the intermediate B. Intermediate B under-
goes sequential anodic oxidation and deprotonation to furnish
the 3-methyl-1-phenyl-4-thiocyanato-1H-pyrazol-5-ol product 4a.
Next, the cathodic reduction of 4a leads to the corresponding enol
anion, which then combines with NH4+ to afford the desired cross-
coupling product 3a. Note that although no base was employed in
the reaction, the cathode reduction of 4a can also form the
corresponding enol anion.
In conclusion, an electrochemical oxidative cross-coupling
reaction between 2.5-substituted-pyrazolin-5-ones and ammonium
thiocyanate has been developed. Under metal catalyst-,
exogenous-oxidant-, and exogenous-electrolyte-free electro-
chemical conditions, a series of unprecedented oxidative
cross-coupling products have been synthesized in up to 97%
yields without silica gel column purification. It is worth noting
that the resulting ammonium oxides are versatile building blocks
for synthesizing other functionalized pyrazole derivatives.
We thank the Jiangxi Normal University for financial support.
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13 CCDC 2041170 (6a).
Conflicts of interest
There are no conflicts to declare.
This journal is The Royal Society of Chemistry 2021
Chem. Commun., 2021, 57, 2768À2771 | 2771