Masato Ohashi

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Organization: Osaka University

Department: Department of Applied Chemistry, Faculty of Engineering

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Chemicals
References

Synthesis, Characterization, and Unique Catalytic Activities of a Fluorinated Nickel Enolate

Co-reporter:Ryohei Doi; Kotaro Kikushima; Masato Ohashi;Sensuke Ogoshi

Journal of the American Chemical Society 2015 Volume 137(Issue 9) pp:3276-3282

Publication Date(Web):February 18, 2015

DOI:10.1021/ja511730k

We have synthesized a new nickel enolate [(PhCOCF2)Ni(dcpe)][FB(C6F5)3] featuring fluorine atoms on the enolate moiety via B(C6F5)3-promoted C–F bond activation of α,α,α-trifluoroacetophenone. X-ray diffraction study of [(PhCOCF2)Ni(dcpe)][FB(C6F5)3] revealed that the complex had adopted an η3-oxallyl coordination mode in the crystal lattice. The reaction of tBuNC with [(PhCOCF2)Ni(dcpe)][FB(C6F5)3] resulted in the coordination of isocyanide to the nickel center to form a C-bound enolate complex. The reactions of [(PhCOCF2)Ni(dcpe)][FB(C6F5)3] with aldehydes gave insertion products quantitatively which were fully characterized by NMR spectroscopy. Furthermore, we established unique catalytic applications for [(PhCOCF2)Ni(dcpe)][FB(C6F5)3] toward a Tishchenko reaction, along with a highly selective crossed-esterification of α,α,α-trifluoroacetophenones with aldehydes.

Nickel-Catalyzed Formation of Fluorine-Containing Ketones via the Selective Cross-Trimerization Reaction of Tetrafluoroethylene, Ethylene, and Aldehydes

Co-reporter:Masato Ohashi; Hiroshi Shirataki; Kotaro Kikushima;Sensuke Ogoshi

Journal of the American Chemical Society 2015 Volume 137(Issue 20) pp:6496-6499

Publication Date(Web):May 8, 2015

DOI:10.1021/jacs.5b03587

In the presence of a catalytic amount of Ni(cod)2 and IPr (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), a cross-trimerization reaction of tetrafluoroethylene (TFE), ethylene, and aldehydes proceeded in a selective manner to afford a variety of 4,4,5,5-tetrafluoro-1-pentanone derivatives in good to excellent yields. The present system involves a five-membered nickelacycle key intermediate generated via the oxidative cyclization of TFE and ethylene.

2,2,3,3-Tetrafluoronickelacyclopentanes Generated via the Oxidative Cyclization of Tetrafluoroethylene and Simple Alkenes: A Key Intermediate in Nickel-Catalyzed C–C Bond-Forming Reactions

Co-reporter:Masato Ohashi, Takuya Kawashima, Tomoaki Taniguchi, Kotaro Kikushima, and Sensuke Ogoshi

Organometallics 2015 Volume 34(Issue 9) pp:1604-1607

Publication Date(Web):April 30, 2015

DOI:10.1021/acs.organomet.5b00218

Oxidative cyclization of tetrafluoroethylene (TFE) and ethylene with Ni(0) resulted in the formation of a five-membered nickelacycle. In the presence of PPh3 as an auxiliary ligand, the partially fluorinated five-membered nickelacycle was isolated and the structure was determined by X-ray analysis. This nickelacycle was found not only to react stoichiometrically with enones to give a cross-trimerization product but also to be a key reaction intermediate in the Ni(0)-catalyzed cotrimerization of TFE and ethylene, leading to 5,5,6,6-tetrafluoro-1-hexene.

Regioselective CF Bond Activation of Hexafluoropropylene on Palladium(0): Formation of a Cationic 2-Perfluoroallylpalladium Complex

Co-reporter:Dr. Masato Ohashi;Mitsutoshi Shibata;Dr. Sensuke Ogoshi

Angewandte Chemie 2014 Volume 126( Issue 49) pp:13796-13800

Publication Date(Web):

DOI:10.1002/ange.201408467

Abstract

A chemoselective C(sp²)F or C(sp³)F bond activation of hexafluoropropylene (HFP) was achieved by adopting the proper combination of a Lewis acid co-additive with a ligand which coordinates Pd⁰. The treatment of [(η²-HFP)Pd(PCy₃)₂] with B(C₆F₅)₃ allowed a chemoselective C(sp³)F bond cleavage of HFP to give a unique cationic perfluoroallypalladium complex. In this complex, the coordination mode of the perfluoroallyl ligand was considered to be of the unique η²-fashion.

Regioselective CF Bond Activation of Hexafluoropropylene on Palladium(0): Formation of a Cationic 2-Perfluoroallylpalladium Complex

Co-reporter:Dr. Masato Ohashi;Mitsutoshi Shibata;Dr. Sensuke Ogoshi

Angewandte Chemie International Edition 2014 Volume 53( Issue 49) pp:13578-13582

Publication Date(Web):

DOI:10.1002/anie.201408467

Abstract

Palladium-Catalyzed Coupling Reaction of Perfluoroarenes with Diarylzinc Compounds

Co-reporter:Dr. Masato Ohashi;Ryohei Doi;Dr. Sensuke Ogoshi

Chemistry - A European Journal 2014 Volume 20( Issue 7) pp:2040-2048

Publication Date(Web):

DOI:10.1002/chem.201303451

Abstract

This report describes the first Pd⁰-catalyzed cross-coupling of hexafluorobenzene (C₆F₆) with diarylzinc compounds to give a variety of pentafluorophenyl arenes. This reaction could be applied to other perfluoroarenes, such as octafluorotoluene, pentafluoropyridine, and perfluoronaphthalene, to give the corresponding polyfluorinated coupling products. The optimal ligand in this catalytic reaction was PCy₃, and lithium iodide was indispensable as an additive for the coupling reaction. One of the roles of lithium iodide in this catalytic reaction was to promote the oxidative addition of one CF bond of C₆F₆ to palladium. Stoichiometric reactions revealed that an expected oxidative-addition product, trans-[Pd(C₆F₅)I(PCy₃)₂], generated from the reaction of [Pd(PCy₃)₂] with C₆F₆ in the presence of lithium iodide, was not involved in the catalytic cycle. Instead, a transient three-coordinate, monophosphine-ligated species, [Pd(C₆F₅)I(PCy₃)], emerged as a potential intermediate in the catalytic cycle. Therefore, we isolated a novel Pd^II complex, [Pd(C₆F₅)I(PCy₃)(py)], in which pyridine (py) acted as a labile ligand to generate the transient species. In fact, in the presence of lithium iodide, this Pd^II complex was found to react smoothly with diphenylzinc to give the desired pentafluorophenyl benzene, whereas the same reaction conducted in the absence of lithium iodide resulted in a decreased yield of pentafluorophenyl benzene, which indicated that the other role of lithium iodide was to enhance the reactivity of the organozinc species during the transmetalation step.

Carbon–Fluorine Bond Activation of Tetrafluoroethylene on Palladium(0) and Nickel(0): Heat or Lewis Acidic Additive Promoted Oxidative Addition

Co-reporter:Masato Ohashi, Mitsutoshi Shibata, Hiroki Saijo, Tadashi Kambara, and Sensuke Ogoshi

Organometallics 2013 Volume 32(Issue 13) pp:3631-3639

Publication Date(Web):June 27, 2013

DOI:10.1021/om400255t

The C–F bond cleavage reaction of tetrafluoroethylene (TFE; CF2═CF2) with an M(0) complex (M = Pd, Ni) was investigated. The treatment of an M(0) precursor with TFE in the presence of the appropriate monodentate phosphine ligand led to a clean formation of the corresponding η2-TFE adduct (η2-TFE)M(PR3)2. In the case of the Ni(0) species, in particular, the choice of phosphine ligands is crucial for the preparation of the desired η2-TFE complex: the use of either PCy3 or PiPr3 resulted in the target adduct, while less sterically hindered phosphines such as PPh3 and PnBu3 gave the known octafluoronickelacyclopentane as a result of the oxidative cyclization of two TFE molecules. Thermolysis of both palladium and nickel η2-TFE adducts bearing PCy3 as the ligand resulted in a C–F bond activation reaction and gave the corresponding (trifluorovinyl)metal fluorides, trans-(PCy3)2M(F)(CF═CF2). The reaction of (η2-TFE)Pd(PPh3)2 with LiI as an additive allowed cleavage of the C–F bond in THF, even at room temperature, and gave trans-(PPh3)2Pd(I)(CF═CF2) with a concomitant formation of lithium fluoride. Other metal halides, such as MgBr2 and AlCl3, also promoted the C–F bond cleavage of TFE. In addition, the use of either BF3·Et2O or B(C6F5)3 exerted a similar accelerative effect on the C–F bond activation of TFE on either nickel or palladium. The molecular structures of a series of η2-TFE and trifluorovinyl complexes were unambiguously determined by means of X-ray crystallography. The resultant (trifluorovinyl)palladium or -nickel species have shown the potential to utilize a key intermediate in cross-coupling reactions with organometallic reagents to prepare a variety of trifluorovinyl compounds.

Nickel-Catalyzed Formation of Cyclopentenone Derivatives via the Unique Cycloaddition of α,β-Unsaturated Phenyl Esters with Alkynes

Co-reporter:Masato Ohashi ; Tomoaki Taniguchi ;Sensuke Ogoshi

Journal of the American Chemical Society 2011 Volume 133(Issue 38) pp:14900-14903

Publication Date(Web):August 30, 2011

DOI:10.1021/ja2059999

Oxygen-containing organic compounds, such as ethers, carboxylates, and carbamates, have recently received increasing attention because of their newly discovered applications as electrophiles in cross-coupling reactions via transition metal-catalyzed C–O bond activation. However, no cycloaddition reaction involving their C–O bond activation has been demonstrated thus far. The present study developed a Ni(0)-catalyzed unique [3+2] cycloaddition reaction of α,β-unsaturated phenyl esters with alkynes in iPrOH to yield cyclopentenone derivatives.

[3 + 3] Cyclodimerization of Methylenecyclopropanes: Stoichiometric and Catalytic Reactions of Nickel(0) with Electron-Deficient Alkylidenecyclopropanes

Co-reporter:Masato Ohashi, Tomoaki Taniguchi and Sensuke Ogoshi

Organometallics 2010 Volume 29(Issue 11) pp:2386-2389

Publication Date(Web):April 30, 2010

DOI:10.1021/om100317y

Stoichiometric treatment of Ni(cod)2 with ethyl cyclopropylideneacetate (ECPA) in the presence of PCy3 resulted in an unpredicted formation of a Ni(0) complex bearing an (E,E)-1,2-bis(exo-alkylidene)cyclohexane ligand, which stemmed from the [3 + 3] cyclodimerization of ECPA. The reaction could be expanded to a Ni(0)-catalyzed [3 + 3] cyclodimerization reaction of ester-substituted methylenecyclopropanes, giving the corresponding cyclohexane derivatives in excellent yields.

Nickel(0)-Catalyzed Formation of Oxaaluminacyclopentenes via an Oxanickelacyclopentene Key Intermediate: Me2AlOTf-Assisted Oxidative Cyclization of an Aldehyde and an Alkyne with Nickel(0)

Co-reporter:Masato Ohashi, Hiroki Saijo, Tomoya Arai, and Sensuke Ogoshi

Organometallics 2010 Volume 29(Issue 23) pp:6534-6540

Publication Date(Web):October 29, 2010

DOI:10.1021/om100857a

The use of Me2AlOTf as an additive allowed the oxidative cyclization of pivalaldehyde and diphenylacetylene with nickel(0) in the presence of PCy3 to give an oxanickelacyclopentene, the structure of which was unambiguously determined by means of X-ray diffraction study. In the presence of TMSCH═CH2, treatment of the oxanickelacyclopentene with an equimolar amount of AlMe3 quantitatively gave an oxaaluminacyclopentene with simultaneous generation of ethane and the Ni(0) species (PCy3)Ni(TMSCH═CH2)2. The oxaaluminacyclopentene was a suitable precursor for the preparation of allylic alcohol derivatives due to its reactive Al−C bond, and treatment with HCl or I2 afforded (E)-4,4-dimethyl-1,2-diphenylpent-1-en-3-ol and (E)-PhCH═C(Ph)CH(tBu)OH, and (Z)-1-iodo-4,4-dimethyl-1,2-diphenylpent-1-en-3-ol and (Z)-PhCI═C(Ph)CH(tBu)OH, respectively, in excellent yield. This sequential reaction was successfully expanded to a Ni(0)-catalyzed three-component cyclocondensation reaction of an aldehyde, an alkyne, and AlMe3 that gave the corresponding oxaaluminacyclopentenes in moderate to good yields. The scope of substrates and the mechanism of the reaction are also reported.