Chemistry: hydrogen at the flick of a switch.
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Masanori Takimoto
Publications and source records attributed to Masanori Takimoto.
Nickel-catalyzed enantioselective three-component coupling of bis-1,3-dienes, aldehydes, and dimethylzinc.
Nickel-catalyzed three-component coupling of bis-1,3-dienes, aldehyde, and dimethylzinc was investigated. In the presence of catalytic amounts of Ni(acac)2 and PPh3, bis-1,3-dienes smoothly react with an aldehyde and dimethylzinc via intramolecular cyclodimerization of bis-1,3-diene moiety. The reaction proceeds through formation of a cyclic bis-allylnickel complex, insertion of an aldehyde, and addition of dimethylzinc to the resulting oxanickellacycle intermediate. An enantioselective coupling was also achieved by the use of a chiral monodentate phosphine ligand, H-MOP.
Aldehydes↗
Nickel-catalyzed regioselective synthesis of tetrasubstituted alkene using alkylative carboxylation of disubstituted alkyne.
[Reaction: see text] Syntheses of alpha-silyl-beta,beta'-dialkyl alpha,beta-unsaturated carboxylic acids were achieved from silylated alkyne, carbon dioxide, and a zinc reagent using a catalytic amount of nickel complex in the presence of an excess amount of DBU. The regioselectivity of the introduction of CO2 into disubstituted alkyne is dependent on the electronic property of the substituent R on the alkyne because the thermodynamic stability of oxanickelacycle IV or V should be affected by conjugation of the substituent R with the carboxyl group in IV or V.
Alkenes↗
Highly enantioselective catalytic carbon dioxide incorporation reaction: nickel-catalyzed asymmetric carboxylative cyclization of bis-1,3-dienes.
A method for nickel-catalyzed asymmetric carbon dioxide (CO2) incorporation via carbon-carbon bond formation was developed. In the presence of a catalytic amount of Ni(acac)2 and MeO-MOP, various bis-1,3-dienes reacted with CO2 (1 atm) and a diorganozinc reagent (Me2Zn or Ph2Zn) to afford cyclic carboxylic acids in good yields (71-100%) and with high enantioselectivities (90-96% ee).
Journal Article↗
Nickel(0)-mediated sequential addition of carbon dioxide and aryl aldehydes into terminal allenes.
[reaction: see text] Nickel-mediated sequential addition of carbon dioxide and aryl aldehydes into terminal allenes is reported. The reaction proceeded in a diastereoselective manner to afford alpha-methylene-gamma-hydroxy carboxylic acids, which allowed stereoselective preparation of cis-beta, gamma-disubstituted alpha-methylene-gamma-lactones.
Journal Article↗
Novel synthesis of heterocycles having a functionalized carbon center via nickel-mediated carboxylation: total synthesis of erythrocarine.
Novel synthetic procedure of heterocycles was developed using nickel-mediated alkylative carboxylation, and the total synthesis of erythrocarine was achieved using this method and RCM of dienyne as the key steps. [reaction: see text]
Alkaloids↗
Novel alkenylative cyclization using a ruthenium catalyst.
Novel alkenylative cyclization of enyne was developed using Cp*RuCl(cod) under ethylene gas at room temperature.
Journal Article↗
Novel Catalytic CO(2) Incorporation Reaction: Nickel-Catalyzed Regio- and Stereoselective Ring-Closing Carboxylation of Bis-1,3-dienes.
Novel nickel-catalyzed carboxylation of bis-1,3-dienes using carbon dioxide (CO2) was investigated. In the presence of catalytic amounts of Ni(acac)2 and PPh3, various bis-1,3-dienes smoothly reacted with CO2 and an organozinc reagent (Et2Zn, Me2Zn, or Ph2Zn) under mild conditions. This catalytic carboxylation process was accompanied by carbocyclization of bis-1,3-diene followed by alkylation by an organozinc reagent to afford cyclic carboxylic acid derivatives in high yields with high regio- and stereoselectivities.
Journal Article↗