R FCO 2H as electron acceptors. The reaction between 2,5-di- tert-butyl-1,4-dimethoxybenzene and R FCO 2H—a hydro-debutylation process

Abstract

▪ By careful EPR, radical scavenging, kinetic, isotope exchange and product studies of the hydro-debutylation process of the titled aryl ether 1 in the media of R FCO 2H (R F=CF 3, n-C 3F 7) with various co-solvents (C 6H 6, n-C 7H 16, THF, PHCOCH 3, (CF 3CO) 2O, CH 3CO 2H and (Cl 3CO 2H) at different temperatures (25⇄70°C), we conclude 1. R FCO 2H may serve as effective one-electron oxidants for generating EPR detectable cation-radicals of various aromatic compounds including aryl ethers, such as 1 in their salutions with none-polar co-solvents. 2. The kinetic studies show that the process obeys the third-order kinetics as following, dp/at=k[ 1 ] 2 · [CF 3CO 2H] 3. All the evidence support our mechanistic rationale that (R FCO 2H 2) + and its π-complex with the titled aryl ether, [R FC(OH) 2… 1 ] + may be the real oxidizing agents. 4. After the electron transfer from 1 to the π-complex, a powerful H-atom donor (R FCO 2H 2) · may he formed, and it in turn, attack the radical cation 1 + in original solvent cage, cause cleavage of Csp 2Csp 3 bond and end up with the final, hydro-debutylation product 2 (2- tert-butyl-1, 4-dimethoxybenzene). 5. This piece of work has opened up, at least, a new facet of the chemistry of perfluorocarboxylic acids and this is worthy to be continued. The rather detailed mechanistic picture, the transition state of the reaction, and the medium and temperature effects on the reaction, are also discussed.