Synergy between bis(dimethyldioctylammonium) molybdate and tetraethylene glycol monooctyl ether: A winning combination for interfacial catalysis in thermo-controlled and switchable microemulsions

• Synergy between dimethyldioctylammonium molybdate and tetraethyleneglycol octyl ether.
• Thermo-responsive catalytic one-phase microemulsion with only 6% of surfactants.
• Efficient [DiC8]2[MoO4]/C8E4/cyclohexane/H2O system for dark singlet oxygenation.
• Separation of products and catalyst in a Winsor I microemulsion at low temperature.

A simple thermo-responsive one-phase microemulsion (μem) is designed to enable the dark singlet oxidation of organic substrates while allowing a straightforward separation of the catalytic surfactant and products in two distinct phases by cooling down the reaction medium. This latter is prepared by combining a small amount (1%) of the catalytic surfactant bis(dimethyldioctylammonium) molybdate, [DiC8]2[MoO4], with the nonionic amphiphile tetraethylene glycol monooctyl ether, C8E4. Tensiometry and dynamic light scattering are used to rationalize the synergy between the two surfactants which strongly interact. The oxidation takes place in the effective one-phase Winsor IV system which separates into two phases (μem + oil, i.e. Winsor I) just by temperature change thanks to the presence of the thermo-sensitive C8E4. The thermal-controlled nanostructured reaction medium is applied to the ene reaction, [4+2] cycloaddition and sulfide oxidation.

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