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,
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.
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).
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.