Pb(OAc)4-Cu(OAc)2-mediated oxidation of 1-alkylcyclohexanols; ?-decomposition of 1-alkylcycloalkoxy radicals

Lead(iv) acetate: intriguing reactivity profile

“…1 Cleavage of glycol 2 and acyloin moieties, 3 oxidative decarboxylation 4 and formation of tetrahydrofurans from alcohols possessing a d-H 5 are the common examples. 13 When R is allyl group (homoallyl alcohol), dramatic rate acceleration with exclusive formation of cycloalkanone and allyl acetate via ''a synchronous two-electron transfer mechanism'' was observed. 7 These developments spurred both theoretical and experimental studies to gain insight into elusive mechanistic aspects.…”

“…12,13 When the solvent is changed to MeOH, the reaction occurs at room temperature furnishing novel methoxy substituted spirocyclic tetrahydrofuran products. 12,13 When the solvent is changed to MeOH, the reaction occurs at room temperature furnishing novel methoxy substituted spirocyclic tetrahydrofuran products.…”

“…Kapustina et al reported that LTA reaction of tertiary alkanols, obtained by nucleophilic addition of R group to cycloalkanone, results in b-fragmentation of the intermediate alkoxy radical leading to unsaturated ketone or cycloalkanone, depending on the structural features of the alkanol. 13 When R is allyl group (homoallyl alcohol), dramatic rate acceleration with exclusive formation of cycloalkanone and allyl acetate via ''a synchronous two-electron transfer mechanism'' was observed.…”

“…The LTA mediated oxidative fragmentation of the allyl group in benzene solvent may be rationalized as follows: at reflux temperature, ligand exchange of one of the acetate groups on LTA with homoallyl alcohol followed by intramolecular coordination of lead with p-bond of allyl group triggers b-fragmentation leading to a-diketone and a p-allyl complex which eventually decomposes to allyl acetate and Pb(OAc) 2 . 12,13 When the solvent is changed to MeOH, the reaction occurs at room temperature furnishing novel methoxy substituted spirocyclic tetrahydrofuran products. It is known that LTA undergoes ligand exchange with MeOH to produce methoxylead(IV) acetate species (Scheme 2).…”

“…§ As evident from the X-ray crystal structures of 1d, 6c, 10c, 13c and 14d, the major isomer in all cases was the one in which the methoxy group on spirocyclic tetrahydrofuran ring is disposed on the beta-face and in case of the minor isomer, the methoxy group is disposed on the alpha-face. The configuration of the remaining compounds was fixed based on the internal consistency in 1 H and 13 C NMR data or analogy.…”