Intramolecular cyclic ether formation versus β-fragmentation in the reaction of saturated aliphatic alcohols with lead tetraacetate

In the reaction of lead tetraacetate with saturated aliphatic alcohols containing an alkyl chain long enough to participate in the cyclization process, it was found that intramolecular tetrahydrofuran formation decreases and β-fragmentation increases in the order: primary alcohol---secondary alcohol---tertiary alcohol, and also in the order: β-unsubstituted alcohol---β-monomethyl substituted alcohol---β,β-dimethyl substituted alcohol. These results are discussed in terms of structural factors (steric and polar effects) which control the rate of the two competing homolytic processes in the intermediate alkoxy radicals, i.e. 1,5-hydrogen transfer from the δ-carbon to the hydroxyl oxygen leading to cyclic ether products and cleavage of the C---βC bond leading to fragmentation products.