Takahiro Iwahama

Aerobic oxidation of alcohols to carbonyl compounds catalyzed by n-hydroxyphthalimide (NHPI) combined with Co(acac)3

Aerobic oxidation of various alcohols has been accomplished by using a new catalytic system, N-hydroxyphthalimide (NHPI) combined with Co(acac)3. The oxidation of alcohols by NHPI was found to be markedly enhanced by adding a slight amount of Co(acac)3 (0.05 equiv. to NHPI). Thus, secondary alcohols and vic-diols which are difficult to be oxidized by NHPI alone were smoothly oxidized with molecular oxygen (1 atm) to the corresponding carbonyl compounds under relatively mild conditions (65 ∼ 75 °C).

Hydroxylation of polycyclic alkanes with molecular oxygen catalyzed by N-hydroxyphthalimide (NHPI) combined with transition metal salts

Adamantanes were successfully converted into the corresponding mono- and dihydroxy adamantanes with molecular oxygen in the presence of N-hydroxyphthalimide (NHPI) combined with cobalt salts under mild conditions. For example, exposure of adamantane under oxygen atmosphere in the presence of NHPI (10 mol%) and Co(acac)2 (0.5 mol%) in acetic acid at 75 °C for 6 h afforded adamantan-1-ol (43 %) and adamantane-1,3-diol (40 %) along with adamantan-2-one (8 %) in 93 % conversion. Similarly, 1,3-dimethyladamantane produced 3,5-dimethyladamantan-1-ol (47 %) and 5,7-dimethyladamantane-1,3-diol (37 %).

A remarkable effect of quaternary ammonium bromide for the N-hydroxyphthalimide-catalyzed aerobic oxidation of hydrocarbons

Abstract A methodology for the aerobic oxidation of organic substrates in the absence of any metal catalyst has been established using combined catalytic system consisting of N -hydroxyphthalimide and quaternary ammonium bromide. Thus, various hydrocarbons were successfully oxidized under dioxygen atmosphere to the corresponding oxygenated compounds in good selectivities.

Oxidation with the “O2−H2O2-vanadium complex-pyrazine-2-carboxylic acid” reagent

The vanadium complex—pyrazine-2-carboxylic acid (PCA) system catalyzes oxidation of styrenes PhRC=CHR′ (R=H, Me; R′=H, Ph), or phenylacetylenes PhC=CR (R=H, Ph) with hydrogen peroxide in air to give aldehydes, ketones, and carboxylic acids. The reaction begins with H2O2 coordination to the vanadium ion followed by the formation of hydroxyl radicals. Catalytic action of PCA facilitates the reduction of the VV complex to the VIV complex and/or the stage of the formation of a peroxide derivative of vanadium.

Selective oxidation of sulfides to sulfoxides with molecular oxygen catalyzed by N-hydroxyphthalimide (NHPI) in the presence of alcohols

Aerobic oxidation of various sulfides using N-hydroxyphthalimide (NHPI) in the presence of alcohols was examined. For instance, the oxidation of diphenyl sulfide in the presence of cyclohexanol and a catalytic amount of NHPI in benzonitrile gave diphenyl sulfoxide in 88 % yield along with a small amount of diphenyl sulfone (7 %). The actual oxidant in this oxidation is considered to be an α-hydroxy hydroperoxide generated by the autoxidation of alcohol assisted by the NHPI which serves as the radical catalyst.

A direct conversion ofvic-diols into 1, 2-diketones with aqueous hydrogen peroxide catalyzed by peroxotungstophosphate (PCWP)

Abstract α-Hydroxy ketones and vic-diols were successfully oxidized to the corresponding diketones with aqueous hydrogen peroxide in the presence of a catalytic amount of peroxotungstophosphate (PCWP). This method provides a straightforward route of 1, 2-diketones which are difficult to prepare by conventional oxidation of vic-diols.

Epoxidation of alkenes using alkyl hydroperoxides generated in situ by catalytic autoxidation of hydrocarbons with dioxygen

Olefins were smoothly epoxidized under O2 (1 atm) in the presence of a hydrocarbon such as ethylbenzene or tetralin, using N-hydroxyphthalimide (NHPI) and Mo(CO)6 as catalyst; the present reaction involves autoxidation of the hydrocarbon assisted by NHPI and epoxidation of alkenes with the resulting hydroperoxide catalyzed by Mo(CO)6; cis-alkene was epoxidized in a stereospecific manner to form the corresponding cis-epoxide in high yield.

Epoxidation of alkenes using dioxygen in the presence of an alcohol catalyzed by N -hydroxyphthalimide and hexafluoroacetone without any metal catalyst

A new approach for the epoxidation of alkenes using O2 without any metal catalyst was developed; a variety of alkenes were epoxidized in a regio- and stereoselective manner with O2 in the presence of benzhydrol catalyzed by N-hydroxyphthalimide and hexafluoroacetone.

The radical-chain addition of aldehydes to alkenes by the use of N-hydroxyphthalimide (NHPI) as a polarity-reversal catalyst

Hydroacylation of simple alkenes with aldehydes via a radical process was successfully achieved by the use of N-hydroxyphthalimide (NHPI) as a polarity-reversal catalyst. Thus, 5-tridecanone was obtained by the reaction of oct-1-ene with pentanal in the presence of small amounts of NHPI and dibenzoyl peroxide (BPO).

Catalytic radical addition of ketones to alkenes by a metal–dioxygen redox system

Radical addition of ketones to alkenes catalyzed by Mn(OAc)2 combined with Co(OAc)2 using dioxygen as oxidant was developed; for instance, the reaction of cyclohexanone with oct-1-ene in the presence of very small amounts of Mn(OAc)2 and Co(OAc)2 under air (1 atm) gave 2-octylcyclohexanone in good selectivity; from styrene, a six-membered cyclic peroxide was isolated in good yield.