Arsines and Arsine Oxides as Catalysts

Inspired by a daim in the patent literature ]27], Sheldon et al. identified di-n-butyl-phenylarsine as a highly active catalyst for the epoxidation of cydohexene as the substrate, and with 60% hydrogen peroxide in TFE as the solvent [28]. Among a series of purely aromatic arsines, electron-rich ones (such as Ph3As) were found to be 

Active oxidant involved in H202-epoxidations catalyzed by (a) arsenic acids, 

By modifying the n-butyl substituents in di-n-butylphenylarsine to —(CH2)2-CgFi7, Sheldon et al. obtained a catalyst system that, in principle, can be recycled by extraction with prefiuorinated solvents [28]. Thus far, the partitioning of the corresponding arsine oxide proved unsatisfactory. Nevertheless, at least partial recovery could be achieved by crystallization from hexane or acetone. 

Epoxidation catalysis by arsonic acids (both free and polymer-bound) had been reported as early as 1979 by Jacobson et al. [29]. However, these early experiments were typically carried out in 1,4-dioxane as solvent. The latter had been identified as an optimal solvent, as it is miscible both with the aqueous oxidant and the organic 

Epoxidations with 60 % H2O2 in 2,2,2-trifluoroethanol (TFE), catalyzed by di-/i-butylphenyl arsine - yield [%], catalyst loading [mol-%], reaction time - 

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