Ring Acyloxylation

Ring Acyloxylation. Soluble and supported palladium catalysts are suitable reagents used to achieve ring acyloxylation of aromatic compounds.499 503 693 780 Reaction conditions, however, are critical since coupling and side chain substitution also occur. 

Acetoxylation of naphthalene was achieved with stoichiometric amount of Pd(OAc)2 or in a catalytic reaction using the Cu2+ + 02 system for the reoxidation of Pd(0) 786 

Highly selective formation of phenyl acetate was observed in the oxidation of benzene with palladium promoted by heteropoly acids.694 Lead tatraacetate, in contrast, usually produces acetoxylated aromatics in low yields due to side reac-tions. Electrochemical acetoxylation of benzene and its derivatives and alkoxylation of polycyclic aromatics789 790 are also possible. Thermal or photochemical decomposition of diacyl peroxides, when carried out in the presence of polycyclic aromatic compounds, results in ring acyloxylation.688 The less reactive 

Near-quantitative yields of aryl isopropyl carbonates were realized in a similar process when diisopropyl peroxydicarbonate was reacted with alkyl-substituted aromatics.794 Substitution is effected by a radical entity possessing a considerable ionic character. 

---

The yields of ring acyloxylation products are improved by carrying out the reaction in CFaCOsH/CFaCOaNa, since the first products, namely trifluoroacetoxylated compounds, are generally stable under the conditions of anodic substitution. ... 

Aromatic acyloxylation can be achieved via the decomposition of diacyl peroxides in the presence of aromatic substrates. By careful choice of reaction conditions, either acyloxylation or trifluoromethylation of the ring system can be achieved, using trifluoroacetyl peroxide generated in situ from trifluoroacetic anhydride and sodium percarbonate (Figure 3.117).492... 

Cyclic peroxides. When a stream of dry air is admitted to the oxidation system including Mn(OAc)3 and Mn(OAc)2], the first C-C bond formation in the reaction of alkenes and jS-keto esters is followed by oxygen trapping and completed by ring closure toward the ketone or aldehyde group. The product yield can be as high as 90%. a -Acyloxylation of enones. ... 

Oxygen Nucleophiles. A reagent such as permanganate oxidizes toluene to benzoic acid, whereas benzylic oxidation by palladium acetate results in benzyl alcohol derivatives. The oxidation is favored by electron-releasing substituents in the phenyl ring. Catalytic amounts of palladium acetate and tin diacetate, in combination with air, effects an efficient palladium-catalyzed benzylic oxidation of toluene and xylenes. For the latter substrates, the Q, Q -diacetate is the main product.A mixed palladium diacetate-copper diacetate catalyst has also been found to selectively catalyze the benzylic acyloxylation of toluene (eq 64). ... 

---