Peroxy esters reactions with copper salts

Oxidation of C—bonds by copper ion catalyzed reaction with an organic peroxy ester (the Kha-rasch-Sosnovsky reaction) was at one time very popular for allylic oxidation and has been thoroughly reviewed. The reaction is usually carried out by dropwise addition of peroxy ester (conunonly r-butyl peracetate or r-butyl perbenzoate) to a stirred mixture of substrate and copper salt (0.1 mol % commonly copper(I) chloride or bromide) in an inert solvent at mildly elevated temperature (60-120 C). The mechanism involves three steps (i) generation of an alkoxy radical (ii) hyttogen atom abstractitm and (iii) radical oxidation and reaction with carboxylate anion (Scheme 11). 

Allylic hydrogens are replaced by acyloxy groups by reaction of peroxy esters in the presence of catalytic amounts of copper salts, including Cu(OAc)2- The reaction probably proceeds via the formation of an aUylic radical, which reacts quickly with Cu to form a Cu intermediate that generates the most substituted aUcene, probably via a pericyclic transition state (eq 6)T Allylic oxidation can be enantioselective when performed in AcOH and pivalic acid in the presence of Cu(OAc)2 and an L-amino acid. ... 

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