Synthesis of trans-1,2-dimetalloalkenes through reductive anti-dimagnesiation and dialumination of alkynes

単純分子から有用物質を短工程で製造可能に --炭素と金属を結ぶ新しい方法により合成効率の飛躍的向上へ--. 京都大学プレスリリース. 2023-01-04.Polar reactive organometallic species have been key reagents in synthesis for more than a century. Stereodefined 1, 2-dimetallated alkenes offer promising synthetic utility; however, few methods are available for their preparation due to their relatively low stability. Here we report the reductive anti-1, 2-dimetallation of alkynes to stereoselectively generate trans-1, 2-dimagnesio- and 1, 2-dialuminoalkenes, which are stable and have been demonstrated in organic synthesis. These stereodefined 1, 2-dimetallated alkenes are prepared through the use of a sodium dispersion as a reducing agent, and organomagnesium and organoaluminium halides as reduction-resistant electrophiles. Highly nucleophilic 1, 2-dimagnesioalkenes serve as dual Grignard reagents and have been demonstrated to react with various electrophiles to afford anti-difunctionalized alkenes. The 1, 2-dialuminoalkenes react with paraformaldehyde with dearomatization of the aryl moieties to form the corresponding dearomatized 1, 4-diols, with the overall reaction being regarded as alkynyl-directed dearomatization of arenes. X-ray crystallographic analysis further supports the formation of trans-1, 2-dimagnesio- and 1, 2-dialuminoalkenes, with computational studies providing insight into the mechanism of dearomative difunctionalization

Chromium carbides and cyclopropenylidenes

Carbon tetrabromide can be reduced with CrBr2 in THF to form a dinuclear carbido complex, [CrBr2(thf)(2))][CrBr2(thf)(3)](mu-C), along with formation of [CrBr3(thf)(3)]. An X-ray diffraction (XRD) study of the pyridine adduct displayed a dinuclear structure bridged by a carbido ligand between 5- and 6-coordinate chromium centers. The carbido complex reacted with two equivalents of aldehydes to form alpha,beta-unsaturated ketones. Treatment of the carbido complex with alkenes resulted in a formal double-cyclopropanation of alkenes by the carbido moiety to afford spiropentanes. Isotope labeling studies using a C-13-enriched carbido complex, [CrBr2(thf)(2))][CrBr2(thf)(3)](mu-C-13), identified that the quaternary carbon in the spiropentane framework was delivered by carbide transfer from the carbido complex. Terminal and internal alkynes also reacted with the carbido complex to form cyclopropenylidene complexes. A solid-state structure of the diethylcyclopropenylidene complex, prepared from 3-hexyne, showed a mononuclear cyclopropenylidene chromium(iii) structure

Structural elucidation of a methylenation reagent of esters: synthesis and reactivity of a dinuclear titanium(iii) methylene complex

Transmetallation of a zinc methylene complex [ZnI(tmeda)](2)(mu-CH2) with a titanium(iii) chloride [TiCl3(tmeda)(thf)] produced a titanium methylene complex. The X-ray diffraction study displayed a dinuclear methylene structure [TiCl(tmeda)](2)(mu-CH2)(mu-Cl)(2). Treatment of an ester with the titanium methylene complex resulted in methylenation of the ester carbonyl to form a vinyl ether. The titanium methylene complex also reacted with a terminal olefin, resulting in olefin-metathesis and olefin-homologation. Cyclopropanation by methylene transfer from the titanium methylene proceeded by use of a 1,3-diene. The mechanistic study of the cyclopropanation reaction by the density functional theory calculations was also reported

Enhanced initial cell responses to chemically modified anodized titanium.

BACKGROUND: Previously, we reported that anodized porous titanium implants have photocatalytic hydrophilicity. However, this effect was not always sufficient for the significant improvement of bone apposition. PURPOSE: The purpose of this study was to improve the photocatalytic properties of porous titanium implants by the fluoride modification of the anodized titanium dioxide (TiO(2)), and to investigate the initial cell response to it. MATERIALS AND METHODS: The ideal concentration of ammonium hydrogen fluoride (NH(4)F-HF(2)) used in this study was determined by a static water contact angle assay. The ideal concentration of NH(4)F-HF(2) was 0.175%, and experimental disks were treated with this concentration. A pluripotent mesenchymal cell line, C2C12, was cultured on the disks in order to investigate cell attachment, morphology, and proliferation. RESULTS: Cell attachment after 30 minutes of culturing was significantly higher for the ultraviolet-irradiated, fluoride-modified anodized TiO(2) (p < .05), and the simultaneous scanning electron microscope observation showed a rather flattened and extended cell morphology. The proliferation rate after 24 hours was also significantly higher for the fluoride-modified anodized TiO(2). CONCLUSION: Fluoride chemical modification enhances the hydrophilic property of the anodized TiO(2) and improves the initial cell response to it

Superhydrophilicity on nano-rough carbon surfaces achieved by hyperthermal oxygen-atom beam exposure

In order to investigate a method to increase hydrophilicity on nano-rough carbon surfaces, a nano-rough surface of C(60) film and an atomically flat surface of highly oriented pyrolytic graphite (HOPG) were oxidized by hyperthermal oxygen-atom beam exposure and the hydrophilicities of the surfaces were investigated. Superhydrophilicity were achieved on these exposed carbon surfaces, which had low O/C ratio of approximately 28% and surface roughness (Ra) of approximately 3 nm. The direct oxidations on sp(2) bonded carbon atoms (basal plane) of these two carbon materials by the exposure of hyperthermal O-atom beam would contribute the superhydrophilicity

ウシ ト ソノ キンエンシュ ノ キョウツウ セッケッキュウ コウゲン

ウシとその近縁家畜に共通する赤血球抗原を特定するために,アジア在来牛,バリウシ,ガヤール,ヤク,スイギュウ,ベゾアー,ヤギおよびヒツジの計1,000頭以上について,32種類のウシ血液型判定用モノクローナル抗体を用いた試験を行なった。これらの家畜はウシと34.4～87.5%の赤血球抗原を共有していた。共通抗原の数から推定すると,ウシ亜属(Bos)とガウア亜属(Bibos)間は,ウシ亜属(Bos)とヤク亜属(Poehagus)間より近縁であった。A2抗原は調べた8種全てに分布する抗原だった。Fc抗原の存在はウシ亜科とヤギ亜科の動物を区別した。すなわちウシ,バリウシ,ガヤール,ヤク,スイギュウのすべての個体がFc抗原を持つのに対し,ヤギやヒツジでFcをもつ個体は認められなかった。To detect common erythrocyte antigens among cattle and their close relatives, extensive tests on red blood cells from more than 1,000 animals including several indigenous cattle from various Asian countries, Bali cattle, Gayal, Yaks, Water buffaloes, Bezoar and some breeds of goats and sheep were screened with thirty-two bovine red blood group monoclonal antibodies. The five species except cattle, Bezoar and Gayal shared 34.4-87.5% of erythrocyte antigens with cattle. Based on the number of common erythrocyte antigens in each species, the relationships between subgenera Bos and Bibos was closer than that between subgenera Bos and Poephagus. The A2 antigen was distributed among all the eight species screened. The presence of the Fc antigen could be used to distinguish subfamily Bovinae from subfamily Caprinae ; that is all individuals of cattle, Bali cattle, Gayal, Yaks and Water buffaloes had the Fc antigen but not goats nor sheep

Reductive anti-dimagnesiation and dialumination of alkynes: Synthesis and reactions of trans-1,2-dimetalloalkenes

Given the great significance of polar reactive organometallic species in synthesis for more than one century, generation and use of stereodefined 1,2-dimetallated alkenes should be fascinating yet has been very challenging. Here we report reductive anti-1,2-dimetalation of alkynes to easily and stereoselectively generate trans-1,2-dimagnesio- and 1,2-dialuminoalkenes that are difficult to prepare, reasonably stable, and thus useful for organic synthesis. The key for the success is the use of sodium dispersion as a powerful reducing agent and organomagnesium and organoaluminum halides as reduction-resistant electrophiles counterintuitively. Highly nucleophilic 1,2-dimagnesioalkenes serve as dual Grignard reagents and react with various electrophiles to afford anti-difunctionalized alkenes. Interestingly, 1,2-dialuminoalkenes react with paraformaldehyde with dearomatization of the aryl moieties to form the corresponding dearomatized 1,4-diols, the overall reaction being regarded as alkynyl-directed dearomatization of arenes. Our anti-1,2-dimetalation including structural and computational investigation provides a new powerful tool and unique insight in the development of organometallic chemistry and organic synthesis

Reductive Ring Opening of Arylcyclopropanecarboxamides Accompanied by Borylation and Enolate Formation

Treatment of arylcyclopropanecarboxamides with a sodium dispersion in the presence of methoxypinacolborane as a reduction-resistant electrophile leads to reductive cleavage of the cyclopropane ring followed by instant trapping with the boron electrophile to yield the enolates of γ-aryl-γ-borylalkanamides. The enolates react further with a different electrophile to yield the corresponding α-substituted amides with anti selectivity