Satoshi Sakaguchi

Beckmann Rearrangement of Ketoximes to Lactams by Triphosphazene Catalyst

Triphosphazene, 1,3,5-triazo-2,4,6-triphosphorine-2,2,4,4,6,6-chloride (TAPC), was found to be an efficient catalyst for the Beckmann rearrangement of cyclohexanone oxime and cyclododecanone oxime to epsilon-caprolactam and laurolactam, which are raw materials of nylon-6 and nylon-12, respectively.

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).

Selective aerobic oxidation of primary alcohols catalyzed by a Ru(PPh3)3Cl2/hydroquinone system

Abstract Aerobic oxidation of primary alcohols to aldehydes was efficiently performed using a Ru(PPh 3 ) 3 Cl 2 /hydroquinone system under atmospheric oxygen at 60 °C. A primary alcohol even in the presence of a secondary one was selectively oxidized to the corresponding aldehyde in high yield.

Addition of aldehydes and their equivalents to electron-deficient alkenes using N-hydroxyphthalimide (NHPI) as a polarity-reversal catalyst

Radical addition of aldehydes and masked aldehydes like 1,3-dioxolanes to electron-deficient alkenes was achieved by the use of catalytic amounts of BPO and N-hydroxyphthalimide (NHPI) as a polarity-reversal catalyst under mild conditions. Three-component radical coupling of 1,3-dioxolanes, maleates, and alkenes was performed in the presence of BPO and NHPI under similar conditions.

Preparation of Hydroperoxides byN-Hydroxyphthalimide-Catalyzed Aerobic Oxidation of Alkylbenzenes and Hydroaromatic Compounds and Its Application

An efficient approach to phenols and aldehydes through the formation of hydroperoxides from alkylbenzenes was successfully achieved by aerobic oxidation using N-hydroxyphthalimide (NHPI) as a catalyst. The oxidation of various alkylbenzenes with dioxygen by NHPI followed by treatment with a Lewis acid or triphenylphosphine led to phenols or aldehydes, respectively, in good yields. For example, the aerobic oxidation of cumene in the presence of a catalytic amount of NHPI at 75 °C and subsequent treatment with H2SO4 gave phenol in 77% yield. 1,4-Dihydroxybenzene (61%) and 4-isopropylphenol (33%) were obtained from 1,4-diisopropylbenzene. On the other hand, dibenzyl ether was converted into phenol or benzaldehyde upon treatment of the resulting hydroperoxide with InCl3 or PPh3, respectively.

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 %).

Synthesis of enol and vinyl esters catalyzed by an iridium complex

Abstract Enol and vinyl esters were successfully synthesized by the use of an iridium complex as a catalyst. The reaction of carboxylic acids with terminal alkynes in the presence of catalytic amounts of [Ir(cod)Cl]2 and Na2CO3 gave the corresponding 1-alkenyl esters. The addition of carboxylic acids to alkynes principally took place in the Markovnikov fashion. In addition, by the use of an Ir complex combined with NaOAc various vinyl esters were prepared through the transvinylation between carboxylic acids and vinyl acetate.

Molybdovanadophosphate (NPMoV)/hydroquinone/O2 system as an efficient reoxidation system in palladium-catalyzed oxidation of alkenes

Abstract Molybdovanadophosphate (NPMoV)/hydroquinone/O 2 system was found to be an efficient reoxidation system in palladium-catalyzed oxidations of alkenes and related compounds. Thus, acetoxylations of cycloalkenes utilizing molecular oxygen as the final oxidant were cleanly performed using the multicatalytic system consisting of Pd(OAc) 2 /hydroquinone/NPMoV to form 3-acetoxy-1-cycloalkenes in good yields. For example, cyclopentene and cyclohexene were converted into the corresponding allylic acetates in almost quantitative yields. Omitting hydroquinone from the catalytic system led to low yields of the acetates. Acetoxylation of cyclooctene was satisfactorily achieved by replacing hydroquinone of the multicatalytic system by chlorohydroquinone. Molybdovanadophosphates, which catalyze the smooth dehydrogenation of hydroquinone to benzoquinone with dioxygen, were found to rapidly promote the present Pd(II)-catalyzed acetoxylation of cycloalkenes. By the use of a mixed solvent of ethanol and water under these conditions, Wacker type oxidations of cyclohexene and styrene were accomplished in fair to good yields. Monosubstituted alkenes such as ethyl acrylate and acrylonitrile underwent the acetalization by the present catalytic system to give the corresponding acetals in quantitative yields.

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.

Aerobic Oxidation of Benzene to Biphenyl Using a Pd(II)/Molybdovanadophosphoric Acid Catalytic System

The oxidative coupling reaction of benzene to biphenyl was examined by the use of a Pd(OAc)2/molybdovanadophosphoric acid/O2 system under mild conditions. Pd(OAc)2 combined with two different types of molybdovanadophosphoric acids exhibited the highest catalytic activity for the biphenyl synthesis. The best turn-over number (TON) of Pd(OAc)2 and the yield of biphenyl reached 109 and 14.3% based on the benzene used, respectively. The rate-determining step of the coupling was found to be the reoxidation step of the reduced molybdovanadophosphoric acid by molecular oxygen.