N-Phosphine Oxide-Substiuted Imidazolylidenes (PoxIms): Multifunctional Multipurpose Carbenes
S. Hazra, Y. Hoshimoto, S. Ogoshi
Chem. Eur. J. 2017, 23, 15238-15243.
This article discusses the concept of N-heterocyclic carbenes (NHCs) equipped with more than one functionality, which allow using these NHCs for multiple purposes. A pioneering example for such NHCs is N-phosphine oxide-substituted imidazolylidenes (PoxIms), and their synthesis and strategic use are highlighted. The utility of PoxIms exceeds by far the conventional use as multidntate ligands for metal complexes on account of the synergetic functions of the carbene and the N-phosphine oxide group(s).
Invited 'Concept' Article; Most Accessed article; Highlited in Frontispiece
Copper-Catalyzed Regioselective Monodefluoroborylation of Polyfluoroalkenes en Route to Diverse Fluoroalkenes
H. Sakaguchi, Y. Uetake, M. Ohashi, T. Niwa, S. Ogoshi, and T. Hosoya
J. Am. Chem. Soc. 2017, 139, 12855-12862.
Monodefluoroborylation of polyfluoroalkenes, such as tetrafluoroethylene, (trifluorovinyl)arenes, (difluorovinyl)arenes, and trifluoromethylated monofluoroalkenes, has been achieved in a regioselective manner under mild conditions via copper catalysis. Stoichiometric experiments indicate that the fate of the regioselectivity depends on the mode of β-fluorine elimination, which depends on the substrate.
Synthesis and Reactivity of Fluoroalkyl Copper Complexes by the Oxycupration of Tetrafluoroehtylene
M. Ohashi, T. Adachi, N. Ishida, K. Kikushima, and S. Ogoshi
Angew. Chem. Int. Ed. 2017, 56, 11911-11915.
The copper(I)-mediated generation of -OCF2CF2- moieties by the oxycupration of tetrafluoroethylene (TFE) using either copper aryloxides or alkoxides is disclosed. The key intermediates, 2-aryloxy-1,1,2,2-tetrafluoroethyl and 2-alkoxy-1,1,2,2-tetrafluoroethyl copper complexes, were obtained from the reaction of the corresponding aryloxy and alkoxy copper complexes with TFE, and their structures in solution and in the solid state were unambiguously determined by multinuclear NMR spectroscopy and X-ray diffraction analysis. These copper complexes subsequently reacted with aryl iodides (ArI) to afford ROCF2CF2Ar (R=aryl or alkyl) in high yields.
Highlighted as a Back Cover Picture
Phosphorylation of Isocyanates and Aldehydes Mediated by Multifunctional N-Phosphine Oxide-Substituted Imidazolylidenes
Y. Hoshimoto, T. Asada, S. Hazra, M. Ohashi, and S. Ogoshi
Chem. Lett. 2017, 46, 1211-1213.
The direct syntheses of imidic-phosphinic mixed anhydrides and phosphinates were accomplished via phosphorylation of isocyanates or aldehydes with N-phosphine oxide-substitued imidazolylidenes (PoxIms) that are equipped with both nucleophilic carbene and electrophilic phosphorus moieties.
Nickel(0)-Catalyzed Coupling Reactions of Carbonyls and Alkenes with Reducing Reagents Giving Six- and Seven-Membered Benzocycloalkanols
Y. Hayashi, Y. Hoshimoto, K. Ravindr,. M. Ohashi, and S. Ogoshi
Chem. Lett. 2017, 46, 1096-1098.
Nickel(0)-catalyzed coupling reactions of 1,6- and 1,7-enals with triethylsilane have been utilized to synthesize six- and seven-membered silyl-protected benzocycloalkanols. When triethylborane was employed, tetralol derivatives were obtained.
Two-step synthesis of chiral fused tricyclic scaffolds from phenols via desymmetrization on nickel
R. Kumar, Y. Hoshimoto, E. Tamai, M. Ohashi, and S. Ogoshi
Nat. Commun. 2017, 8, 32.
Here we show a nickel-catalyzed highly enantioselective synthesis of hydronaphtho[1,8-bc]furans with five contiguous chiral centers via desymmetrization of alkynyl-cyclohexadienone by oxidative cyclization and following formal [4 + 2] cycloaddition processes. Alkynyl-cyclohexadienone was synthesized in one step from easily accessible phenols. This reaction represents excellent chemo-selectivity, regio-selectivity, diastereo-selectivity, and enantio-selectivity (single diastereomer, up to 99% ee).
OPEN ACCESS; Press Release; Highlighted in 日刊工業新聞(6月30日), Nature Japan, Chem-Station
Efficient Synthesis of Polycyclic γ-Lactams by Catalytic Carbonylation of Ene-Imines via Nickelacycle Intermediate
Y. Hoshimoto, K. Ashida, Y. Sasaoka, R. Kumar, K. Kamikawa, X. Verdaguer,
A. Riera, M. Ohashi, and S. Ogoshi
Angew. Chem. Int. Ed. 2017.56, 8206-8210.
CO gas is employed in a nickel(0)-catalyzed [2+2+1] carbonylative cycloaddition reaction with 1,5- and 1,6-ene-imine substrates. The method affords a variety of tri- and tetracyclic γ-lactams in excellent yields with 100 % atom efficiency.
Most Accessed article
Copolymerisation of ethylene with polar monomers by using palladium catalysts bearing an N-heterocyclic carbene-phosphine oxide bidentate ligand
W. Tao, S. Akita, R. Nakano, S. Ito, Y. Hoshimoto, S. Ogoshi and K. Nozaki
Chem. Commun. 2017, 53, 2630-2633.
We report the synthesis and characterization of palladium complexes bearing an N-heterocyclic carbene-phosphine oxide bidantate ligand and their use as catalysts for ethylene polymerization and ethylene/polar monomer copolymerization.
Nickel(0)-Mediated Transformation of Tetrafluoroethylene and Vinylarenes into Fluorinated Cyclobutyl Compounds
M. Ohashi, Y. Ueda and S. Ogoshi
Angew. Chem. Int. Ed. 2017, 56, 2435-2439.
In the presence of Ni(0)/PCy3, styrene was found to participate in oxidative cyclization with tetrafluoroethylene, thus leading to the corresponding nickelacycle with a unique η3-π-benzyl structure. In addition, the flexibility of the coordination mode in the η3-benzyl moiety allowed the partially fluorinated nickelacycle to undergo unprecedented amine-induced α-fluorine elimination, thus leading to the construction of a fluorinated cyclobutyl skeleton.
Kinetic and Theoretical Studies on Ni(0)/N-Heterocyclic Carbene-Catalyzed Intramolecular Alkene Hydroacylation
Y. Hoshimoto, Y. Hayashi, M. Ohashi, and S. Ogoshi
Chem. Asian J. 2017, 12, 278-282.
A monomeric and trans-nickelacycle intermediate was found to be key for occurance of the rate-limiting β-hydride elimination in Ni(0)/ItBu-catalyzed intramolecular alkene hydroacyaltion, which was revealed by a combined kinetic and theoretical study.
Strategic Utilization of Multifunctional Carbene for Direct Synthesis of Carboxylic-Phosphinic Mixed Anhydride from CO2
Y. Hoshimoto, T. Asada, S. Hazra, T. Kinoshita, P. Sombut, R. Kumar, M.
Ohashi, and S. Ogoshi
Angew. Chem. Int. Ed. 2016, 55, 16075-16079.
Strategic utilization of N-phosphine oxide-substituted imidazolylidenes enabled a direct preparation of a novel carboxylic-phosphinic mixed anhydride from carbon dioxide, which was followed by efficient derivatization into a variety of carbonyl compounds.
Transition-Metal Mediated Transformations of Tetrafluoroethylene into Various Polyfluorinated Organic Compounds
M. Ohashi, and S. Ogoshi
有機合成化学協会誌 (J. Synth. Org. Chem., Jpn.), 2016, 74, 1047-1057.
This account describes our studies on the transition-metal mediated transformation of tetrafluoroethylene into a variety of polyfluorinated organic compounds, manifesting merits of a derivatization of readily available perfluorinated compounds to valuable highly fluorinated organic compounds.
Nickel-Catalyzed Enantioselective Synthesis of Cyclobutenes via [2+2] Cycloaddition of α,β-Unsaturated Carbonyls with 1,3-Enynes
R. Kumar, E. Tamai, A. Ohnish, A. Nishimura, Y. Hoshimoto, M. Ohashi,
and S. Ogoshi
Synthesis. 2016, 48, 2789-2794.
A nickel(0)-catalyzed enantioselective approach has been developed for [2+2] cycloaddition of alkenes with conjugated enynes for the first time. A new chiral NHC was synthesized to yield cyclobutenes in good yields and enantioselectivities.
Highlighted as a Front Cover Picture
Ni(0)-catalyzed intramolecular reductive coupling of alkenes and aldehydes or ketones with hydrosilane
Y. Hayashi, Y. Hoshimoto, R. Kumar, M. Ohashi, and S. Ogoshi
Chem. Commun. 2016, 52, 6237-6240.
A nickel(0)-catalyzed reductive coupling of aldehydes and simple alkenes with hydrosilanes has been developed. The present system was also applied to a reductive coupling with ketones. Preliminary results of a nickel(0)-catalyzed asymmetric three-component coupling reaction of an aldehyde, an alkene, and triethylsilane are also shown.
Copper-Catalyzed Reaction of Trifluoromethylketones with Aldehydes via a Copper Difluoroenolate
R. Doi, M. Ohashi, and S. Ogoshi
Angew. Chem. Int. Ed. 2016, 55, 341-344.
A copper-catalyzed reaction of easily accessible α,α,α-trifluoromethylketones with various aldehydes affords difluoro-methylene compounds in the presence of diboron and NaOtBu. The key process of the reaction is the formation of a copper difluoroenolate by 1,2-addition of a borylcopper intermediate to α,α,α-trifluoromethylketones and subsequent
Highlight: Synfacts (Synfacts 2016, 12, 78)