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Nishimura K., Xu S., Nishii Y., et al. One-Step Synthesis of Benzophosphole Derivatives from Arylalkynes by Phosphenium-Dication-Mediated Sequential C-P/C-C Bond Forming Reaction. Organic Letters. 25(9), 1503-1508, 10 March 2023; © 2023 American Chemical Society. https://doi.org/10.1021/acs.orglett.3c00263., A metal-free, phosphenium-dication-mediated sequential C-P and C-C bond forming reaction has been developed. This protocol can provide concise access to the (di)benzophosphole derivatives in one synthetic operation from the readily available and simple arylalkynes and phosphinic acids. Application to the multiple cyclization reaction and the fully intermolecular three-component-coupling-type reaction are also described.

This is the accepted version of the following article: Nakamura Shotaro, Okubo Kohei, Nishii Yuji, et al. Stimuli‐Responsive Properties on a Bisbenzofuropyrazine Core: Mechanochromism and Concentration‐Controlled Vapochromism. Chemistry – A European Journal, e202302605 (2023), which has been published in final form at https://doi.org/10.1002/chem.202302605. This article may be used for non-commercialpurposes in accordance with the Wiley Self-ArchivingPolicy [https://authorservices.wiley.com/author-resources/Journal-Authors/licensing/self-archiving.html], Stimulus-responsive organic materials with luminescence switching properties have attracted considerable attention for their practical applications in sensing, security, and display devices. In this paper, bent-type bisbenzofuropyrazine derivatives, Bent-H and Bent-sBu, with good solubilities were synthesized, and their physical and optical properties were investigated in detail. Bent-H gave three crystalline polymorphs, and they showed different luminescence properties depending on their crystal packing structures. In addition, Bent-H exhibited mechanochromic luminescence in spite of its rigid skeleton. Bent-sBu exhibited unique concentration-dependent vapochromic luminescence. Ground Bent-sBu was converted to blue-emissive, green-emissive, and green-emissive high-viscosity solution states at low, moderate, and high concentrations of CHCl3 vapor, respectively. This finding represents a concentration-dependent multi-phase transition with an organic solvent, which is of potent interest for application in sensing systems.

This is an Accepted Manuscript of an article published by Taylor & Francis in Phosphorus, Sulfur, and Silicon and the Related Elements on 6 Dec 2022, available at https://doi.org/10.1080/10426507.2022.2152815., Sulfur-containing functional groups, among various coordinating functions, have recently attracted attention as useful directing groups for the direct catalytic C-H transformation of aromatic and heteroaromatic compounds. Herein we briefly summarize our recent work on the site-selective substitution on indole and naphthalene skeletons using thioether directing groups under either Cp*Rh(III) or Cp*Ir(III) catalysis. The thioether groups can readily be removed and transformed to other functional groups. The reactions developed appear to be of importance in pharmaceutical and materials chemistry.

Kojima Y., Nishii Y., Hirano K.. Ligand-Enabled Copper-Catalyzed Regio- and Stereoselective Allylboration of 1-Trifluoromethylalkenes. Organic Letters. 24(40), 7450-7454, 14 October 2022; https://doi.org/10.1021/acs.orglett.2c03024., A copper-catalyzed regio- and stereoselective allylboration of 1-trifluoromethylalkenes with bis(pinacolato)diboron (pinB-Bpin) and allylic chlorides has been developed to form functionalized trifluoromethylated products with high diastereoselectivity. The key to success is the judicious choice of Cs2CO3 base and t-Bu-modified dppe-type ligand, which enables the otherwise challenging high catalyst turnover and suppression of the competing defluorination side reaction from an alkylcopper intermediate. The product derivatization of the resulting Bpin moiety can deliver diverse CF3-containing molecules with high stereochemical fidelity.

Kitano J., Nishii Y., Miura M.. Selective Synthesis of C4-Functionalized Benzofurans by Rhodium-Catalyzed Vinylene Transfer: Computational Study on the Cyclopentadienyl Ligand. Organic Letters. 24(31), 5679-5683, (2022), 12 August 2022; ©2022 American Chemical Society. https://doi.org/10.1021/acs.orglett.2c02030., Benzofuran is a privileged structure in many bioactive compounds; however, the controlled synthesis of C2,C3-non-substituted benzofurans has been scares. In particular, cumbersome multistep processes are inevitable for the most inaccessible C4-substituted isomers. Herein, we report a Rh-catalyzed direct vinylene annulation of readily available m-salicylic acid derivatives with vinylene carbonate to achieve selective construction of C4-substituted benzofurans. The Weinreb amide directing group facilitated the following product derivatization. The reaction mechanism was investigated by DFT calculations.

Xu-Xu Q.F., Nishii Y., Miura M.. Synthesis of Diarylselenides through Rh-Catalyzed Direct Diarylation of Elemental Selenium with Benzamides. Journal of Organic Chemistry. 87(24), 16887-16894, (2022), 16 December 2022; ©2022 American Chemical Society. https://doi.org/10.1021/acs.joc.2c02131., Diarylselenides are a representative class of molecules in organoselenium compounds. We herein report a Rh-cata-lyzed direct diarylation of selenium with benzamide derivatives. The use of elemental selenium as the Se source is intriguing in the view of atom economy, cost, stability, and handling. A series of diarylselenides with amide moieties were readily accessible through the directed C–H activation. The intermediacy of electrophilic Se(IV) species was indicated by the control experiments.

This is an Accepted Manuscript of an article published by Taylor & Francis in Phosphorus, Sulfur, and Silicon and the Related Elements on 6 Dec 2022, available at https://doi.org/10.1080/10426507.2022.2152815., Sulfur-containing functional groups, among various coordinating functions, have recently attracted attention as useful directing groups for the direct catalytic C-H transformation of aromatic and heteroaromatic compounds. Herein we briefly summarize our recent work on the site-selective substitution on indole and naphthalene skeletons using thioether directing groups under either Cp*Rh(III) or Cp*Ir(III) catalysis. The thioether groups can readily be removed and transformed to other functional groups. The reactions developed appear to be of importance in pharmaceutical and materials chemistry.

This is an Accepted Manuscript of an article published by Thieme Publishing Group in Journal Title on Publication Date, available online at https://doi.org/10.1055/a-1472-1059., An iridium-catalyzed acylmethylation and a rhodium-catalyzed amidation of naphthalene derivatives are reported, adopting sulfoxonium ylides and dioxazolones as carbene and nitrene transfer agents, respectively. The use of SMe group as a directing group was key to ensure the peri -selective functionalization, and it can be easily removed or diversely transformed to other synthetically useful functionalities after the catalysis.

This is the accepted version of the following article: Xu-Xu Q.F., Nishii Y., Uetake Y., et al. Synthesis of Benzoisoselenazolones via Rh(III)-Catalyzed Direct Annulative Selenation by Using Elemental Selenium. Chemistry - A European Journal 27, 17952 (2021); which has been published in final form at https://doi.org/10.1002/chem.202103485. This article may be used for non-commercialpurposes in accordance with the Wiley Self-ArchivingPolicy [https://authorservices.wiley.com/author-resources/Journal-Authors/licensing/self-archiving.html], Isoselenazolone derivatives have attracted significant research interest because of their potent therapeutic activities and indispensable applications in organic synthesis. Efficient construction of functionalized isoselenazolone scaffolds is still challenging, and thus new synthetic approaches with improved operational simplicity have been of particular interest. In this manuscript, we introduce a rhodium-catalyzed direct selenium annulation by using stable and tractable elemental selenium. A series of benzamides as well as acrylamides were successfully coupled with selenium under mild reaction conditions, and the obtained isoselenazolones could be pivotal synthetic precursors for several organoselenium compounds. Based on the designed control experiments and X-ray absorption spectroscopy measurements, we propose an unprecedented selenation mechanism involving a highly electrophilic Se(IV) species as the reactive selenium donor. The reaction mechanism was further verified by a computational study.

Kurose R., Nishii Y., Miura M.. Metal-Free Direct Trifluoromethylthiolation of Aromatic Compounds Using Triptycenyl Sulfide Catalyst. Organic Letters. 23(6), 2380-2385, (2021), 19 March 2021; ©2021 American Chemical Society. https://doi.org/10.1021/acs.orglett.1c00727., Herein we report an efficient synthetic method for the electrophilic trifluoromethylthiolation of aromatic compounds. The key is to use triptycenyl sulfide (Trip-SMe) and TfOH to enhance the electrophilicity of SCF3 fragment through the formation of sulfonium intermediates. This method enables direct installation of an SCF3 group onto unactivated aromatics at room temperature adopting a commercially available saccharin-based reagent. Preliminary DFT calculation was carried out to investigate the substitu-tion effect on the catalytic activity.

Moon S., Nishii Y., Miura M.. Synthesis of Isothiazoles and Isoselenazoles through Rhodium-Catalyzed Oxidative Annulation with Elemental Sulfur and Selenium. Organic Letters. 23(1), 49-53, (2021), 1 January 2021; ©2021 American Chemical Society. https://doi.org/10.1021/acs.orglett.0c03674., A rhodium-catalyzed oxidative annulation of benzimidates with elemental sulfur for the direct construction of isothi-azole rings is reported. The proposed reaction mechanism involving Rh(I)/Rh(III) redox is supported by a stoichiometric reaction of metallacycle species as well as DFT calculations. This method is also applicable to the selenium cyclization to produce isoselenazole derivatives. The alkoxy substituent at the C3 position can be used for further functionalization of the azole cores.

Kato M., Ghosh K., Nishii Y., et al. Rhodium-catalysed direct formylmethylation using vinylene carbonate and sequential dehydrogenative esterification. Chemical Communications 57, 8280 (2021); https://doi.org/10.1039/D1CC03362J., A rhodium-catalysed direct formylmethylation adopting vinylene carbonate as an ethynol equivalent is reported. The developed catalytic system is further utilised for the oxidant-free production of esters with the liberation of hydrogen gas. Some control experiments are conducted to elucidate the reaction mechanism.

Ueno K., Nishii Y., Miura M.. Electrophilic substitution of asymmetrically distorted benzenes within triptycene derivatives. Organic Letters. 23(9), 3552-3556, (2021), 7 May 2021; ©2021 American Chemical Society. https://doi.org/10.1021/acs.orglett.1c00970., Herein we disclose a unique directing effect of 9-substituted triptycenes in electrophilic substitution to achieve the regioselective functionalization of the triptycene core. The Hirshfeld population analysis was adopted to predict the selectivity in electrophilic substitution. TMS and t-Bu groups were found to considerably accelerate the reaction at C2 positions to produce C3-symmetric isomers. Correlation between distortion and charge distribution within benzene rings was systematically examined.

Kona C.N., Nishii Y., Miura M.. Sulfur-Directed C7-Selective Alkenylation of Indoles under Rhodium Catalysis. Organic Letters. 23(16), 6252-6256, (2021), 20 August 2022; ©2021 American Chemical Society. https://doi.org/10.1021/acs.orglett.1c01990., Regioselective direct functionalization of an indole benzenoid fragment has been a significant challenge be-cause of its inherently lower reactivity. In this report, we introduce a Rh-catalyzed C7-selective alkenylation of indole de-rivatives utilizing a new sulfur directing group N-SCy. A notable feature of this system is that the directing group is readily installed to the indoles and easily removed after the catalysis under mild conditions.

Takishima R., Nishii Y., Miura M.. Synthesis and Optical Properties of Axially Chiral Bibenzo[ b]carbazole Derivatives. Organic Letters. 23(4), 1349-1354, (2021); 19 February 2021: ©2021 American Chemical Society. https://doi.org/10.1021/acs.orglett.1c00011., Pure organic materials with the circularly polarized luminescence (CPL) property have attracted significant research interest over the past few decades. In this study, a series of axially chiral bibenzo[b]carbazole derivatives were synthesized by adopting palladium- and iridium-catalyzed direct C–H functionalization reactions as the key steps. These compounds exhibited CPL characteristics with considerably large dissymmetry factors up to 2.81 × 10–2 in the solid state, indicating the formation of well-ordered aggregates.

Beilstein J. Org. Chem. 2020, 16, 325–336. doi:10.3762/bjoc.16.32, A series of optically active bisbenzofuro[2,3-b:3′,2′-e]pyridine (BBZFPy) derivatives was synthesized starting with the readily available (S)- and (R)-1,1′-bi-2-naphthols through a palladium-catalyzed multiple intramolecular C-H/C-H coupling as the key ring-closure step. The effect of terminal tert-butyl substituents on the BBZFPy skeleton was systematically investigated to uncover a unique aggregation-induced enhancement of CPL characteristics in the solid state. The crystal structures of the coupling products were also evaluated by single crystal X-ray analysis and the well-ordered intermolecular stacking arrangements appeared to be responsible for the enhanced CPL.

This is the peer reviewed version of the following article: Moon S., Kato M., Nishii Y., et al. Synthesis of Benzo[b]thiophenes through Rhodium-Catalyzed Three-Component Reaction using Elemental Sulfur. Advanced Synthesis and Catalysis 362, 1669 (2020); which has been published in final form at https://doi.org/10.1002/adsc.202000112. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited., A benzo[b]thiophene synthesis by Rh-catalyzed three-component coupling reaction of arylboronic acids, alkynes, and elemental sulfur (S8) is developed. A notable feature of this protocol is that the thienannulation (thiophene annulation) proceeds with high regioselectivity via the sequential alkyne insertion, C−H activation, and then sulfur atom transfer to the metallacycle intermediate. In a similar manner, dibenzothiophenes can be synthesized from the parent biarylboronic acids and S8. (Figure presented.).

Nishii Y., Miura M.. Cp*M-Catalyzed Direct Annulation with Terminal Alkynes and Their Surrogates for the Construction of Multi-Ring Systems. ACS Catalysis. 10(17), 9747-9757, (2020), 4 September 2020; ©2020 American Chemical Society. https://doi.org/10.1021/acscatal.0c02972., Transition-metal-catalyzed C–H activation followed by oxidative cyclization with unsaturated coupling partners has been a valuable synthetic tool for the multi-ring molecular scaffolds. This Perspective introduces the recent progress on the Cp*M-catalyzed (M = Co, Rh, and Ir) oxidative direct annulation of functionalized arenes with terminal alkynes and their equivalents through C–H bond cleavage. The highlighted examples are categorized according to the ten different types of reagents used in the transfor-mations. The representative conditions, selected examples of the reaction scope, and key mechanistic aspects are briefly summarized.

Mihara G., Ghosh K., Nishii Y., et al. Concise Synthesis of Isocoumarins through Rh-Catalyzed Direct Vinylene Annulation: Scope and Mechanistic Insight. Organic Letters. 22(14), 5706-5711, (2020), 17 July 2020; ©2020 American Chemical Society. https://doi.org/10.1021/acs.orglett.0c02112., Transition-metal-catalyzed activation of inert C–H bonds and subsequent C–C bond formation have emerged as pow-erful synthetic tools for the synthesis of elaborate cyclic molecules. In this report, we introduce an efficient synthetic method of 3,4-unsubstituted isocoumarins adopting an electron deficient CpERh complex as the catalyst. The use of vinylene carbonate as a vinylene transfer reagent enables the direct construction of isocoumarins from readily available benzoic acids, without any external oxidants as well as bases. The reaction mechanism is evaluated by computational analysis to find an unprecedented “rhodium shift” event within the catalytic cycle.

Mihara G., Noguchi T., Nishii Y., et al. Rhodium-catalyzed annulative coupling of isothiazoles with alkynes through n-s bond cleavage. Organic Letters. 22(2), 661-665, (2020), 17 January 2020; ©2020 American Chemical Society. https://doi.org/10.1021/acs.orglett.9b04437., A Rh(III)-catalyzed annulative coupling of 3,5-diarylisothiazoles and alkynes is reported. The N–S bond in the isothi-azole ring acts as an internal oxidant to regenerate the Rh(III) species in combination with an external Cu(II) oxidant, and the corre-sponding 1:2 coupling products are obtained. The remarkable difference in the reaction outcome between isothiazoles and the relevant isoxazoles has been investigated by DFT calculations, revealing that the relative stability of the enolate intermediates dictates the product selectivity.

A site-selective direct CH arylation protocol for the triptycene skeleton is developed using copper catalyst and diaryliodonium reagents. With the aid of directing groups, C₃-symmetric trisubstituted triptycenes are selectively synthesized, and the structure was determined by X-ray diffraction analysis. Further derivatization of the installed bromo functionalities is also described.

Noguchi T., Nishii Y., Miura M.. Rhodium-Catalyzed Cascade Annulative Coupling of 3,5-Diarylisoxazoles with Alkynes. Synthesis (Germany) 51, 258 (2019); https://doi.org/10.1055/s-0037-1610376., A rhodium-catalyzed cascade annulative coupling of 3,5-diarylisoxazoles with three equivalents of an alkyne proceeds smoothly in the presence of a Cu(II) oxidant, where the sequential construction of isoquinoline and naphtho[1,8- bc ]pyran frameworks connected by a biaryl linkage is achieved by a single operation. Most of the obtained polycyclic compounds exhibit visible fluorescence in both the solution and the solid state. The hexaphenylated isoquinoline-naphthopyran conjugate (R = Ph) as a representative product shows a green emission which can be turned off by making an isoquinolinium salt with an acid. The emission is also reversibly turned on by treatment with a base.

Ghosh K., Nishii Y., Miura M.. Rhodium-Catalyzed Annulative Coupling Using Vinylene Carbonate as an Oxidizing Acetylene Surrogate. ACS Catalysis. 9(12), 11455-11460, (2019), 6 December 2019; ©2019 American Chemical Society. https://doi.org/10.1021/acscatal.9b04254., Transition-metal-catalyzed C–H activation and subsequent oxidative cyclization with alkynes has been a pow-erful tool for the synthesis of polycyclic aromatic compounds. Despite the substantial progress in this field, it is still a significant challenge to establish synthetic methodologies for the construction of non-substituted vinylene-fused aromatics. We herein report a Rh(III)-catalyzed C–H/N–H annulation with vinylene carbonate as an acetylene surrogate. Vinylene carbonate also acts as an internal oxidant to regenerate the Rh(III) species in situ; thus no external oxidant is required to trigger the oxidative annulation. This protocol is applicable to the direct synthesis of various N-heteroaromatics.