Cp*M-Catalyzed Direct Annulation with Terminal Alkynes and Their Surrogates for the Construction of Multi-Ring Systems

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.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

Measurement of root system with growth of oriental pickling melon.

It is important to clarify how the soil moisture changes by irrigation and how moisture is consumed by absorption of root, to plan irrigation appropriately in upland field. And, it is thought that clarifying the growth of the root can be important information in the water management, because the amount and the pattern of root water uptake change depending on the growth stage. However, there are not too much a lot of researches that measure the root, in addition, the example intended for crops of 'Gourd family (scientific name:Cucurbitaceae)' is not found. Therefore, for oriental pickling melon, it measured how for the root system to grow up as crop grew every three weeks. The results of this study may be summarized as: 1) Root amount increased with the growth of crops, and the majority of the root existed to 20cm in depth. A lot of rootlets with the role of water uptake existed outside of from 10 to 20cm. 2) Root length has grown up in horizontal and vertical direction at a dash at the stage of growing initial. 3) It was able to be confirmed to the growth of the ground part and the root that the length and amount either also had implications. Moreover, root amount and plant caver ratio drew similar curve

Synthesis and Optical Properties of Axially Chiral Bibenzo[ b]carbazole Derivatives

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.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

Rhodium-Catalyzed Cascade Annulative Coupling of 3,5-Diarylisoxazoles with Alkynes

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.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

Synthesis of Isothiazoles and Isoselenazoles through Rhodium-Catalyzed Oxidative Annulation with Elemental Sulfur and Selenium

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.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

Copper-catalyzed site-selective direct arylation of triptycene

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

Oxidative C-H/C-H Annulation of Imidazopyridines and Indazoles through Rhodium-Catalyzed Vinylene Transfer

Transition-metal-catalyzed C−H activation followed by oxidative annulation with alkynes has been an efficient syn-thetic tool for the assembly of various poly-aromatic scaffolds. Despite the substantial progress in this field, it is still a significant challenge to achieve the synthesis of non-substituted vinylene-fused compounds. In this contribution, we report a Rh-catalyzed C−H/C−H vinylene cyclization adopting vinylene carbonate as a “vinylene transfer” agent. This protocol achieves the direct annula-tive π-extension of imidazole- and pyrazole-fused aromatics.Ghosh K., Nishii Y., Miura M.. Oxidative C-H/C-H Annulation of Imidazopyridines and Indazoles through Rhodium-Catalyzed Vinylene Transfer. Organic Letters. 22(9), 3547-3550, (2020), 1 May 2020; ©2020 American Chemical Society. https://doi.org/10.1021/acs.orglett.0c00975

Selective Synthesis of C4-Functionalized Benzofurans by Rhodium-Catalyzed Vinylene Transfer: Computational Study on the Cyclopentadienyl Ligand

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.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

Electrophilic substitution of asymmetrically distorted benzenes within triptycene derivatives

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.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