ja9807892_si_001.pdf (574.63 kB)
New Strategies in Carbonylation Chemistry: The Synthesis of δ-Lactones from Saturated Alcohols and CO
journal contribution
posted on 1998-08-11, 00:00 authored by Shinji Tsunoi, Ilhyong Ryu, Tohru Okuda, Minoru Tanaka, Mitsuo Komatsu, Noboru SonodaThis paper describes the δ-carbonylation of saturated alcohols which uses a 1,5-hydrogen-transfer
reaction of alkoxyl radicals and subsequent carbonylation at the δ-carbon atoms as the key. The carbonylation
reactions of five classes of saturated alcohols, namely, primary alcohols having primary δ-carbons, primary
alcohols having secondary δ-carbons, primary alcohols having tertiary δ-carbons, secondary alcohols having
primary δ-carbons, secondary alcohols having secondary δ-carbons, were carried out, in which lead tetraacetate
(LTA) was used as a one-electron oxidant to generate the alkoxyl radicals. Carbonylation of these saturated
alcohols, except for primary alcohols having tertiary δ-carbons, took place to afford δ-lactones in moderate to
good yields. The mechanism of the remote carbonylation likely involves (1) alkoxyl radical generation via
LTA oxidation of a saturated alcohol, (2) conversion of this alkoxyl radical to a δ-hydroxyalkyl radical by a
1,5-hydrogen-transfer reaction, (3) CO trapping of the δ-hydroxyalkyl radical yielding an acyl radical, and (4)
oxidation and cyclization of the acyl radical to give a δ-lactone. A metal salt-free system was also tested for
a substrate derived from a tertiary alcohol having a secondary δ-carbon; the photolysis of an alkyl
4-nitrobenzenesulfenate under CO pressures gave a δ-lactone in moderate yield.