The oxidation of a number of secondary alcohols (i.e., 2-propanol, 1-phenyl ethanol, 3-octanol, cyclobutanol, exo- and endo-2-norborneol) by methyl(trifluoromethyl)dioxirane (1b) affords the corresponding ketones in high yield (92-99%), under mild conditions and within short reaction times (2-20 min). Primary alcohols 1-butanol and benzyl alcohol are converted by 1b into butyric acid, and into PhCHO/PhCO2H mixtures, respectively, while t-butanol is not appreciably oxidized. The oxidation of cyclohexanol by 1b follows a second-order rate-law, and a kinetic isotope effect (kH/kD) = 1.6 ± 0.15 was measured using cyclohexanol-d11. Remarkable stereoselectivity was recorded in the oxidation of 2-norborneol, since the endo-alcohol was found to be ca. 40 times more reactive than its exo-stereomer. The available evidence suggests that a radical-chain mechanism is unlikely for the title transformation.
Selective oxidation of alcohols by dioxiranes
Fusco C;
1991
Abstract
The oxidation of a number of secondary alcohols (i.e., 2-propanol, 1-phenyl ethanol, 3-octanol, cyclobutanol, exo- and endo-2-norborneol) by methyl(trifluoromethyl)dioxirane (1b) affords the corresponding ketones in high yield (92-99%), under mild conditions and within short reaction times (2-20 min). Primary alcohols 1-butanol and benzyl alcohol are converted by 1b into butyric acid, and into PhCHO/PhCO2H mixtures, respectively, while t-butanol is not appreciably oxidized. The oxidation of cyclohexanol by 1b follows a second-order rate-law, and a kinetic isotope effect (kH/kD) = 1.6 ± 0.15 was measured using cyclohexanol-d11. Remarkable stereoselectivity was recorded in the oxidation of 2-norborneol, since the endo-alcohol was found to be ca. 40 times more reactive than its exo-stereomer. The available evidence suggests that a radical-chain mechanism is unlikely for the title transformation.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
