In situ formation of peracetic acid in iron-catalyzed epoxidations by hydrogen peroxide in the presence of acetic acid

Iron complexes (tpa)Fe( OTf)₂ (1) and (bpmen)Fe(OTf)₂ (2) [tpa = tris-(2-pyridylmethyl)-amine; bpmen = N,N′-bis-(2- pyridylmethyl)-N,N′-dimethyl-1,2-ethylenediamine] were found to catalyze the in situ formation of AcOOH from H₂O₂ and AcOH in the course of olefin oxidations. While oxidation of cyclooctene by H ₂O₂ catalyzed by 1 gives nearly equimolar epoxide and cis-diol products, introduction of AcOH to the reaction greatly enhances the selectivity for epoxidation. The resulting product distribution is nearly identical to that of cyclooctene oxidation by AcOOH catalyzed by 1. The in situ generation of AcOOH from H₂O₂ and AcOH in epoxidation catalyzed by some iron complexes opens a possibility to attain AcOOH-type efficiency of epoxidation using H₂O₂ as a terminal oxidant.