Tohru Yamada 교수

Silver-catalyzed reactions are some of the important methodologies in organic chemistry. Since 2007, a new application of silver catalysts has been emerging. For the sequential carboxylation and cyclization of alkyne derivatives, such as propargyl alcohols and amines, using carbon dioxide, silver catalysts show significant reactivity under mild conditions unlike other transition metals. These developments have received much attention for the effective utilization of carbon dioxide in organic che

Abstract In the presence of a bis(1,3-diketonato)nickel(II) complex, various olefins are directly monooxygenated into the corresponding epoxides on treatment with atmospheric pressure of oxygen or air and aldehydes. Especially, it is noted that bis[1,3-bis(p-methoxyphenyl)-1,3-propanedionato]nickel(II) behaves as an excellent catalyst in the present epoxidation.

Abstract Enantioselective epoxidation of unfunctionalized olefins with combined use of molecular oxygen, an oxidant, and pivalaldehyde, a reductant, was demonstrated in the presence of a catalytic amount of optically active Mn(III)-salen complexes. Dihydronaphthalene derivatives were converted into the corresponding optically active epoxides in good yields with 60–77% enantiomeric excesses.

Abstract In the presence of a catalytic amount of a bis(1,3-diketonato)nickel(II) complex, trisubstituted and exo-terminal olefins or norbornene analogues are smoothly monooxygenated into the corresponding epoxides in high to quantitative yields on treatment with aldehyde under an atmospheric pressure of oxygen at room temperature.

A catalytic amount of silver benzoate with 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) was an effective catalytic system for the reaction of carbon dioxide with various ketones containing an alkyne group at an appropriate position. These reactions afforded the corresponding γ-lactone derivatives in good to high yields under mild conditions.

Abstract In the presence of a catalytic amount of a nickel(II) complex coordinated with 1,3-diketone, various cyclic or acyclic ketones are converted into the corresponding lactones or esters by the Baeyer–Villiger oxidation on treatment with an atmospheric pressure of molecular oxygen (oxidant) and an aldehyde (reductant) at room temperature.

Abstract Enantioselective epoxidation of unfunctionalized olefins is achieved by the combined use of molecular oxygen and pivalaldehyde in the presence of a catalytic amount of optically active Mn(III)–salen complexes. N-Alkylimidazoles are effective axial ligands to produce optically active epoxides with high enantioselectivities in the present procedure; that is, 1,2-dihydronaphthalene derivatives and 2,2-dialkyl-2H-chromene derivatives are converted into the corresponding optically active epo

The highly enantioselective borohydride reduction of aromatic ketones or imines to the corresponding alcohols was developed in the presence of a catalytic amount of an optically active cobalt(II) complex catalyst. This enantioselective reduction is carried out using a precisely premodified borohydride with alcohols such as tetrahydrofurfuryl alcohol, ethanol and methanol. High optical yields are obtained by choosing the appropriate alcohol as modifiers and a suitable beta-ketoiminato ligand of t

The silver salt catalyzed the C-C bond forming reaction of o-alkynylacetophenone derivatives and carbon dioxide. In this reaction, a carbonyl group and a furan skeleton were successively constructed to afford the corresponding dihydroisobenzofuran derivatives.

Highly substituted 2-cyclopentenones were stereospecifically and regioselectively constructed with high catalytic efficiency through Lewis-acid catalyzed decarboxylative Nazarov cyclization of the cyclic carbonate derivative, which is prepared by reacting the propargyl alcohol with carbon dioxide in the presence of a silver catalyst. The stereochemistry of the 2-cyclopentenone is strictly controlled by the geometry of the alkene in the starting material. This method is applicable for various sub

Abstract The oxidation of aldehydes into the corresponding carboxylic acids using a catalytic amount of nickel(II) complex under an oxygen atmosphere at room temperature is described. Bis[1,3-di(p-methoxyphenyl)-1,3-propanedionato]nickel(II)(Ni(dmp)2) behaves as an excellent catalyst for the oxidation of aldehydes to afford the corresponding carboxylic acids in good yields.

Abstract The enantioselective oxidation of olefins with OsO4 coordinated by chiral diamines derived from L-tartaric acid is described. Phenylketene dimethylacetal and trans-stilbene are converted to (R)-methyl mandelate and (1R,2R)-1,2-diphenyl-1,2-ethanediol with moderate and high enantioselectivity, respectively.

Abstract The enantioselective borohydride reduction catalyzed by cobalt(II) complex was successfully applied to 1,4-reduction of β,β-disubstituted α,β-unsaturated carboxamides. In the presence of less than 1 mol% of optically active aldiminato cobalt(II) complex catalyst, the corresponding carboxamides were obtained in high yields with high enantiomeric excesses.

Abstract In the presence of a catalytic amount of bis(dipivaloylmethanato)manganese(II) (= Mn(dpm)2), various cholesterol derivatives are smoothly converted into the corresponding β-epoxides in good to high yields with combined use of molecular oxygen and isobutyraldehyde. These stereoselectivities are the reversal of the cases using peracid such as mCPBA.

Catalytic enantioselective Claisen rearrangement was drastically enhanced under microwave irradiation conditions without any loss of the enantioselectivity. Based on Arrhenius plots it was revealed that enantioselectivity decreased as the internal reaction temperature increased. Therefore, this reaction acceleration would NOT be caused by only a simple thermal effect.