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Enantioselective reduction of ketones with (EtO) 2 MeSiH catalyzed by an in-situ generated N -heterocyclic carbene (NHC) Ir complex at room temperature has been developed. A series of benzimidazolium salts were synthesized and screened in the asymmetric hydrosilylation reaction. As a result, propiophenone was efficiently reduced by the combined catalytic system of [IrCl(cod)] 2 and NHC–Ag complex derived from N -(1-naphthalenylmethyl)-substituted benzimidazolium salt L12 , affording the corresponding alcohol in 92% yield and with 92% ee. Moreover, the evaluation of an Ir catalyst precursor showed that cationic [Ir(cod) 2 ]BF 4 complex could be used. Furthermore, the introduction of a chiral hydroxyamide side arm into the benzimidazolium salt was critical for the successful design of the NHC ligand.

C 2 -symmetric ester-amide functionalized azolium salt was synthesized from readily available α-amino ester such as L -serine methyl ester. The combination of a Cu salt and the chiral azolium salt promoted the asymmetric conjugate addition reaction of enones with dialkylzincs. Thus, treatment of acyclic enone such as chalcone with Et 2 Zn afforded the corresponding 1,4-adduct with up to 85% ee. An excellent ee value of 93% was obtained when 3-nonen-2-one was reacted with Et 2 Zn. The present catalytic system was found to be useful for the 1,4-addition reaction of cyclic enone. For example, the reaction of 2-cyclohepten-1-one with Et 2 Zn produced ( R )-3-ethylcycloheptanone with 80% ee.

Direct conversion of benzene to phenol was achieved by allowing it to react with a mixed gas of air and CO in the presence of HPMoV and a very small amount of 5%Pd/C in aqueous acetic acid at 150 °C for 2 h. The TON of HPMoV for the formation of phenol goes up to over 1300. The active species of the present reaction is thought to be V4+ generated from HPMoV catalyst by the reduction with CO. The role of the Pd species seems to promote the generation of V4+ from HPMoV. This method is expected to provide a direct route to phenol from benzene.

Carboxylation of benzenes with CO was successfully achieved by a combined catalytic system of Pd(OAc)2 with H5PMo10V2O40·nH2O (HPMo10V2) under the influence of O2 to form the corresponding benzoic acids in relatively high selectivity and moderate yields. The regioselectivity in the carboxylation of alkylbenzenes with CO was dominated by the steric factor rather than the electronic effect of substituents. However, the carboxylation of benzoic acid proceeded with high ortho-selectivity to give phthalic acid in preference to terephthalic acid, which shows coordination of Pd species to the carboxyl group of benzoic acid.

Concomitant introduction of COOH and OH groups to biphenyl was achieved by allowing biphenyl to react with CO and O2 using the Pd/molybdovanadophosphoric acid catalytic system. For instance, biphenyl reacted under a mixed gas of CO (0.5 atm) and O2 (0.5 atm) in the presence of catalytic amounts of Pd(OAc)2 and H5PMo10V2O40·26H2O in acetic acid to give the corresponding hydroxybiphenylcarboxylic acids. The reaction was found to proceed through the formation of biphenylcarboxylic acid followed by hydroxylation of the resulting carboxylic acid.

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.

Various organic compounds were oxidized by molecular oxygen in the presence of a catalytic amount of mixed-addenda heteropolyoxometalates containing molybdenum and vanadium. The catalytic activity of the molybdovanadophosphate was found to be greatly enhanced by supporting on charcoal. The supported catalyst has high catalytic activity for oxidative dehydrogenation of benzylic and allylic alcohols to the corresponding aldehydes and ketones (46–92%), nevertheless, the non-supported catalyst was inactive for the same oxidations under these conditions. 2,3,6-Trimethylphenol was selectively oxidized to trimethyl-p-benzoquinone, which is a precursor of vitamin E, in the presence of a catalytic amount of molybdovanadophosphate. In addition, the aerobic oxidation of amines, alkyl-substituted phenols, and alkanes were also examined.