The mechanism of the rearrangement of β-acyloxyalkyl radicals

Abstract

Determination of the distribution of products from decarbonylation of 2-formyl-1,1-dimethylethyl heptanoate (6d) and other esters of 3-hydroxy-3-methylbutanal, and from the reaction of tributylstannane with 2-bromo-1,1-dimethylethyl benzoate (11b), 2-bromo-1-methyl-1-phenylethyl acetate (11c), and similar bromo-esters, has enabled the rates of rearrangement of some β-acyloxyalkyl radicals to be evaluated. The kinetic data together with the results of reactions using ¹⁸O labelled substrates indicate that 1,2-acyloxy-transfer proceeds via a concerted mechanism involving a five-membered cyclic transition state. The rate of rearrangement of the 2-acetoxy-2-phenylpropyl radical (12c) by 1,2-aryl migration has also been determined.