DFT study on the mechanism of simultaneous trifluoromethylation and
oximation of aryl-substituted ethylene.
Abstract
The effects of different substituents located at the para position of
the aromatic ring and β carbon atom of the styrene on the reaction were
investigated. The results showed that the reaction steps with higher
energy barriers changed a little with the substituents of the reactants,
which indicates that the reaction has a good adaptability to reactants
containing different substituents. It was found the proton transfer in
the final tautomerism step of nitroso intermediate to oxime is the rate
limiting step under anhydrous conditions. Although the solvent effect
did not influence the the rate limiting step significantly, the water
mediated proton transfer significantly decreased the energy barrier of
final tautomerism step. Compared with the direct proton transfer in
vacuum, the energy barrier of the final tautomerism step decreased from
57.80kcal/mol in vacuum to 12.98kcal/mol with the water mediated proton
transfer in water, which declined by 77.5%. When water participates in
rate-limiting steps in organic solvents, the energy barrier also
decreases significantly, which indicates that a small amount of water in
the organic solvent is conducive to the reaction. This study is of great
significance for the application of bifunctionalized reaction in the
synthesis of organic fluoride compounds with different substituents.