Organometallic Chemistry OGOSHI Lab.

Reversible Modulation of the Electronic and Spatial Environment around Ni(0) Centers Bearing Multifuctional Carbene Ligands with Triarylaluminum

Y. Yamauchi, Y. Mondori, Y. Uetake, Y. Takeuchi, T. Kawakita, H. Sakurai, S. Ogoshi, Y. Hoshimoto
ChemRxiv. 2023, preprint (DOI: 10.26434/chemrxiv-2023-5nz52).
We demonstrate a Lewis-acid-mediated reversible expansion, contraction, and transformation of the spatial environment surrounding nickel(0) centers that bear N-phosphine oxide-substituted N-heterocyclic carbenes. The multinuclear NMR, IR, and XAS analyses clarified the details of the changes in the electronic states on the Ni centers. The results presented in this work thus provide a strategy for reversibly modulating the electronic and spatial environment of organometallic complexes, in addition to the well-accepted Lewis-base-mediated ligand-substitution methods.

Regioselective C-F Bond Transformations of Silyl Difluoroenolates

R. Doi, K. Kajiwara, T. Negoro, K. Koh, S. Ogoshi
ChemRxiv. 2023, preprint (DOI: 10.26434/chemrxiv-2023-tszsc).
Herein, we report the development of a nickel-catalyzed cross-coupling reaction of silyl difluoroenolates with aryl zinc reagents via C−F bond cleavage. Treatment of a stoichiometric amount of Ni(0)/ N-heterocyclic carbene (NHC) with silyl difluoroenolates in the presence of a lithium salt resulted in C−F bond cleavage to selectively afford the corresponding (Z)-alkenyl Ni complexes. Density functional theory (DFT) calculations revealed the importance of the silyl substituent in creating environments with varying steric hindrance for each of the two fluorine atoms. Based on these observations, we developed a catalytic cross-coupling reaction that selectively delivers a single geometric isomer of a fluoroenolate.

Nickel-catalyzed exhaustive hydrodefluorination of perfluoroalkyl arenes

R. Doi, M. Yasuda, N. Kajita, K. Koh, S. Ogoshi
J. Am. Chem. Soc. accepted.
ChemRxiv. 2023, preprint (DOI: 10.26434/chemrxiv-2023-9tkg4).
Perfluoroalkyl compounds are persistent environmental pollutants due to their strong C(sp3)−F bonds. Hydrodefluorination has emerged as a potential alternative disposal method for perfluoroalkyl compounds. Although the transformation of trifluoromethyl arenes into the corresponding methyl arenes has been studied by several research groups, hydrodefluorination reactions of longer perfluoroalkyl chains remain rare. Herein, we report exhaustive hydrodefluorination reactions of pentafluoroethyl arenes and longer-chain analogues using molecular nickel catalysis. Despite the cleavage of multiple C(sp3)−F bonds, the reaction already proceeds upon gentle heating. A mechanistic investigation indicated that the reaction proceeds via benzylic hydrodefluorination reactions followed by homobenzylic ones. We reveal the multiple roles of the Ni catalyst, which include C−F bond cleavage, promotion of HF elimination, and hydrosilylation.

Photocatalyst-Free Visible Light-Mediated C-H Perfluoroalkylation of Quinazolin-4(3H)-ones with perfluoroalkyl iodides

T. Delouche, A. Gadiry-Diallo, T. Besson, S. Ogoshi, C. Fruit
Synthesis accepted.
A practical and sustainable photocatalyst-free protocol for photo-induced synthesis of perfluoroalkylated quinazolin-4(3H)-ones is described starting from quinazolin-4(3H)-ones. A wide range of substituted or fused-quinazolinones is found to be compatible, providing the corresponding mono- and bis-perfluoroalkylated compounds in moderate yields. This visible-light mediated C-H perfluoroalkylation allows an environmentally friendly and straightforward access to an array of unprecedented functionalized quinazolinone scaffolds, presenting attractive features for drug discovery. The control experiments demonstrated that a radical mechanism is involved in the reaction mechanism.

N-Borane-Substituted Cyclic Phosphine Imides (BCPIs)

S. Nagai, T. Hinogami, S. Ogoshi, Y. Hoshimoto
ChemRxiv. 2023, preprint (DOI: 10.26434/chemrxiv-2023-qv422-v2).
Herein, we have designed and prepared a novel class of phosphine imides known as N-borane-substituted cyclic phosphine imides (BCPIs). Given a characteristic nucleophilic/Lewis basic reactivity of BCPIs, we represent the first experimental demonstration that a λ5-oxazaphosphetane species is a key intermediate in the transformation of CO₂ using phosphine imides. Moreover, although it has been previously considered unlikely, the spontaneous heterolysis of a B‒Cl bond in a BCPI-coordinated chloroborane has been directly observed, suggesting that such process is a plausible key step in the Lewis acid-promoted generation of borenium species from chloroboranes.

Transformation of Tetrafluoroethylene using Transition-Metal Complexes

R. Doi, Y. Zhou, S. Ogoshi
Synthesis 2023, 55, 857..
This review highlights studies on the transformation of TFE into organofluorine compounds using transition-metal complexes, except for polymerizations. Our review covers cross-coupling reactions via C−F bond cleavage, fluoroalkylation reactions, multi-component couplings, and olefin metathesis.

Complexation-Induced N-P Axial Chiraity in Sm(II) N-Phosphine-Oxide-Substituted Imidazolylidene and Imidazolinylidene Complexes

Y. Hoshimoto, Y. Yamauchi, T. Terada, S. Ogoshi
Can. J. Chem. 2022, in press.
ChemRxiv. 2022, preprint (DOI: 10.26434/chemrxiv-2022-rf1wd)
Two types of Sm(II) complexes bearing either an N-phosphine-oxide-substituted imidazolylidene (PoxIm) or the corresponding imidazolinylidene (SPoxIm) were successfully prepared and characterized using single crystal X-ray diffraction analysis. In some cases, axial chirality was clearly induced around the N-P bonds.
Invited contribution to "the Crudden Special Issue"

Main-group catalysis for H2 purification based on liquid organic hydrogen carriers

T. Hashimoto, T. Asada, S. Ogoshi, Y. Hoshimoto
Sci. Adv. 2022, 8, eade0189.
ChemRxiv. 2022, preprint (10.26434/chemrxiv-2022-pgbgd)
Here, we demonstrate a strategy to separate H₂ from a gaseous mixture of H₂/CO/CO₂/CH₄ and simultaneously store it in N-heterocyclic compounds that act as liquid organic hydrogen carriers (LOHCs), which can be applied to produce H₂ by subsequent dehydrogenation. A newly designed shelf-stable triaryl borane is able to catalyze the hydrogenation of the N-heteroaromatic compounds in the co-presence of substantial amounts of CO, CO₂, CH₄, and H₂O (i.e., the simultaneous separation and storage of H₂), and to promote the subsequent dehydrogenation (i.e., H₂ recovery), both of which proceed under the solvent-free conditions.
OPEN ACCESS; Press Release；Featured at EurekAlert; AlphaGalileo; Asia Research News; PhysOrg; Scienmag; Nanowerk; 時事通信; YAHOO!; Cosmos Magazine; 日経xTech; Chem-Station;現代化学（東京化学同人, 2023年1月号）

Room-Temperature Reversible Chemisorption of Carbon Monoxide on Nickel(0) Complexes

Y. Yamauchi, Y. Hoshimoto, T. Kawakita, T. Kinoshita, Y. Uetake, H. Sakurai, S. Ogoshi
J. Am. Chem. Soc. 2022, 144, 8818-8826.
ChemRxiv. 2022, preprint (10.26434/chemrxiv-2022-nb0fw)
Herein, we report a pressure-responsive nickel(0)-based system that is able to reversibly chemisorb carbon monoxide (CO) at room temperature. The use of N-heterocyclic carbene ligands with hemi-labile N-phosphine oxide substituents facilitates both the adsorption and desorption of CO on nickel(0) via ligand substitution. Ionic liquids were used as the reaction medium to enhance the desorption rate and establish a reusable system.
OPEN ACCESS; Press Release；現代化学（東京化学同人, 2022年７月号）；Chem-Station

Overlooked Factors Required for Electrolyte Solvents in Li-O2 Battery: Capabilities of Quenching 1O2 and Forming Highly-decomposable Li2O2

K. Nishioka, M. Tanaka, H. Fujimoto, T. Amaya, S. Ogoshi, M. Tobisu, S. Nakanishi
Angew. Chem. Int. Ed. 2022, 61, e202112769..

A Boron-Transfer Mechanism Mediating the Thermally Induced Revival of Frustrated Carbene−Borane Pairs from their Shelf-Stable Adducts

Y. Hoshimoto, M. Sakuraba, T. Kinoshita, M. Ohbo, M. Ratanasak, J. Hasegawa, S. Ogoshi
Commun. Chem.2021, 4, 137.
ChemRxiv. 2021, preprint (DOI: 10.26434/chemrxiv.14462391.v1)
Combined experimental and theoretical studies allowed clarifying the reaction mechanism for the revival of frustrated carbene−borane pairs from external-stimuli-responsive classical Lewis adducts comprised of N-phosphine oxide-substituted imidazolylidenes and triarylboranes. A borane-transfer process from the carbene carbon atom to the N-phosphinoyl oxygen atom was identified as the rate-determining event for the regeneration of the FLP species, eventually enabling the heterolytic cleavage of H2.
Open Access

多用途な多官能基化環状カルベンPoxImの開発

山内　泰宏、星本　陽一、生越　專介
有機合成化学協会誌, 2021, 79, 632-641. (in Japanese; 総合論文)
Practical methods have been established for the synthesis of multifunctional N-heterocyclic carbenes (NHCs) via the introduction of substituents on either the nitrogen atom(s) or the backbone of the NHCs. However, their use has been mainly limited to acting as multidentate ligands for metal complexes. Herein, results of our recent studies on the synthesis and application of N-phosphine oxide-substituted imidazolylidenes (PoxIms) as novel type of multifunctional NHCs are discussed.

Development and Mechanistic Studies of E-Selective Isomerization/Tandem Hydroarylation Reactions of Alkenes with a Nickel(0)/Phosphine Catalyst

H. Iwamoto, T. Tsuruta, S. Ogoshi
ACS Catal. 2021, 11, 6741-6749.
Herein, we report the reaction of terminal alkenes with the nickel(0)/PAd₂(n-Bu) catalyst selectively afforded the corresponding (E)-alkenes. Furthermore, sequential hydroarylations occured when aryl boronic acids were added under the same reaction conditions. A combined experimental and computational mechanistic studies suggested that the isomerization reactions occurred via an intramolecular 1,3-hydrogen shift and an intermolecular hydrogen shift. Moreover, a concerted multi-bond recombination with boronic-acid-assisted oxidative protometallation of the alkene was newly found as an important step for the formation of the alkylnickel(II) species in the hydroarylation.

Sm(II)-Mediated Single-Electron Reduction of Pentafluorophenylcopper(I)

Y. Yamauchi,† S. Nagai† T. Terada, Y. Hoshimoto, S. Ogoshi
(†These authors equally contributed to this work)
Chem. Lett. 2021, 50, 1394-1396.
The single-electron-transfer reduction of pentafluorophenylcopper(I) using the Sm(II) reagents resuted in the formation of ion-paired [Sm(II)][Cu(C6F5)2] species with the concomitant generation of Cu(0).
Open Access

N‐Phosphine Imide‐Substituted Imidazolylidenes (PimIms)

Y. Hoshimoto, S. Nagai, T. Hinogami, S. Hazra, S. Ogoshi
Asian J. Org. Chem. 2021, 10, 1085-1089.
A series of novel multifunctional carbenes of the type N-phosphine imide‐substituted imidazolylidenes (PimIms) has been synthesized and characterized. Substituents including (+)-10-camphorsulfonyl and pyroglutamate groups were introduced on the N-phosphinimidoyl moiety to diversify available structures of isolable carbenes.
Invited contribution to "Early Carrer Special Collections"

Synthesis of Fluoroalkyl Sulfides via Additive-Free Hydrothiolation and Sequential Functionalization Reactions

D. E. Sunagawa, N. Ishida, H. Iwamoto, M. Ohashi, C. Fruit, S. Ogoshi
J. Org. Chem. 2021, 86, 6015-6024.
A modular synthetic method, involving a hydrothiolation, silylation, and fluoroalkylation, for the construction of highly functionalized fluoroalkyl sulfides has been developed. The use of aprotic polar solvents enables the additive-free chemoselective hydrothiolation of tetrafluoroethylene, trifluorochloroethylene, and hexafluoropropene with various thiols. The stepwise functionalization reactions convert the hydrothiolated intermediates into the tetrafluoroethyl sulfides in high efficiency. The method avoids the use of the environmental pollutant Halon-2402, which was employed as a building block in a reported synthetic route.

Development of Metal Complexes Equipped with Structurally Flexible Carbenes

Y. Hoshimoto, S. Ogoshi
Bull. Chem. Soc. Jpn. 2021, 94, 327-338
We herein summarize our recent results on the design and application of metal complexes that bear N-phosphine-oxide-substituted imidazolylidenes (PoxIms), in which the volume and shape of the reaction space around the carbene atoms can be drastically changed via the rotation of the N-phosphinoyl groups; this phenomenon is discussed in detail based on experimental and theoretical results.
Open Access; Award Accounts; Inside Cover

Copper(I)-Mediated C–N/C–C Bond-Forming Reaction with Tetrafluoroethylene for the Synthesis of N-Fluoroalkyl Heteroarenes via an Azacupration/Coupling Mechanism

N. Ishida, T. Adachi, H. Iwamoto, M. Ohashi, S. Ogoshi
Chem. Lett. 2021, 50, 442-444.
A novel copper-mediated N-fluoroalkylation of heteroarenes has been developed. Treating an in-situ-generated N–Cu complex with tetrafluoroethylene (TFE) in the presence of iodoarenes furnished the corresponding N- and aryl-difunctionalized tetrafluoroethanes in up to 98% yield. This method enables the synthesis of tetrafluoroethylene-bridged heteroarenes in a one-pot reaction.