Article
Chemistry, Physical
Dai-Yu Li, Rui-Mu Yu, Jin-Ping Li, Deng-Feng Yang, Qi Pang, Hong-Liang Li
Summary: This article describes an improved para-selective C(sp(2))-H borylation of anisole derivatives. The selective borylation is likely to be influenced by the change in electron density on the aromatic ring when a Lewis acid coordinates with an anisole substrate. In addition, the use of a sterically hindered bipyridyl ligand in the reaction also promotes para-selectivity. This strategy has demonstrated a significant improvement in the ratio of para-borylated products, with the reaction taking place at milder temperatures and most substrates displaying moderate to good site-selectivity.
Article
Chemistry, Multidisciplinary
Hao Zheng, Chang-Hui Liu, Xiao-Yu Wang, Yan Liu, Bing-Zhi Chen, Yan-Cheng Hu, Qing-An Chen
Summary: This article reports an efficient iridium-catalyzed meta-selective C-H borylation reaction that allows for the rapid synthesis of various boronic esters based on benzoferrocenes, ferrocenes, ruthenocene, and related half sandwich complexes. This method does not require preinstalled directing groups and is compatible with a wide range of electron-deficient and -rich functional groups. The scalability and diverse applications of this reaction, including the conversion of boron to heteroatoms and cross-coupling reactions, are also demonstrated.
Article
Chemistry, Multidisciplinary
Yuncong Luo, Shengjie Jiang, Xin Xu
Summary: This work reports a novel site-selective C-H borylation reaction of pyridines at the ortho-position using a yttrocene catalyst, enabling the introduction of boronate groups. The resulting boronates exhibit a broad substrate scope and high atom efficiency, and can undergo various transformations.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Chemistry, Organic
Shuai Mao, Bo Yuan, Xinyu Wang, Yahao Zhao, Lu Wang, Xue-Yan Yang, Yi-Ming Chen, San-Qi Zhang, Pengfei Li
Summary: This study presents a regioselective ortho,ortho'-diborylation of aromatic triazenes catalyzed by [Ir(OMe)(cod)](2) in near-quantitative yields without an additional ligand. The synthesized products can undergo a variety of transformations, providing a short entry to densely functionalized arenes.
Review
Chemistry, Multidisciplinary
Hui Cao, Qiang Cheng, Armido Studer
Summary: The pyridine moiety is widely used in the synthesis of drugs, agrochemicals, catalysts, and functional materials. While direct functionalization of ortho- and para-positions is well-established, meta-selective pyridine C-H functionalization presents more challenges due to the inherent electronic properties of pyridines. In this review, we summarize the current methods for meta-C-H functionalization of pyridines, including the use of directing groups, non-directed metalation, and temporary dearomatization strategies. Recent advances in ligand control and temporary dearomatization are highlighted, while the advantages and limitations of these techniques are discussed, aiming to inspire further developments in this important area.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Organic
Jagriti Chaturvedi, Chabush Haldar, Buddhadeb Chattopadhyay
Summary: This work summarizes the constitutional challenge of an electrostatically directed meta borylation reaction of sterically biased and unbiased substrates. Using a developed strategy, a wide range of challenging substrates can be selectively borylated at the meta position. Furthermore, the reaction proceeds at moderate temperature without the need for synthesizing complex ligand/templates.
Article
Chemistry, Physical
Jonathan Trouve, Purushothaman Rajeshwaran, Michele Tomasini, Antoine Perennes, Thierry Roisnel, Albert Poater, Rafael Gramage-Doria
Summary: Selective C-H bond borylation of challenging pyridines and imidazoles can be achieved in very short reaction times using a supramolecular approach. The catalyst used has a highly rigid zinc-porphyrin substrate-recognition site and a triazolopyridine chelating fragment attached to iridium. The selectivity of the borylation reaction is determined by the distance between the active site and the molecular recognition site, and is independent of the coordinating fragment to iridium. The understanding of the catalyst deactivation pathways led to the identification of a supramolecular catalyst that bypasses these pathways and provides a suitable balance of steric and electronic effects.
Article
Chemistry, Multidisciplinary
Zhong Liu, Zhu-Jun Shi, Lu Liu, Ming Zhang, Meng-Chen Zhang, Hao-Yang Guo, Xiao-Chen Wang
Summary: Asymmetric intermolecular C-H functionalization of pyridines at C3 is achieved by tandem borane and iridium catalysis. The protocol involves borane-catalyzed pyridine hydroboration to generate nucleophilic dihydropyridines, followed by enantioselective iridium-catalyzed allylation of the dihydropyridine, and then oxidative aromatization using air as the oxidant to obtain C3-allylated pyridines. This method allows for the direct synthesis of C3-allylated pyridines with excellent enantioselectivity (up to >99% ee) and is applicable for late-stage functionalization of pyridine-containing drugs.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Multidisciplinary
Daniel Marcos-Atanes, Cristian Vidal, Claudio D. Navo, Francesca Peccati, Gonzalo Jimenez-Oses, Jose L. Mascarenas
Summary: Iridium-catalyzed borylations of aromatic C-H bonds allow for the synthesis of a wide variety of ortho-borylated derivatives. A subtle change in the bipyridine ligand, introducing a CF3 substituent at position 5, enables a complete change of regioselectivity in the borylation of aromatic amides. Computational studies suggest that this regio- and chemoselectivity is due to unusual outer-sphere interactions between the amide group of the substrate and the CF3-substituted aryl ring of the bipyridine ligand.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Physical
Chalachew Mebrahtu, Ruiyan Sun, Christian Henning Gierlich, Regina Palkovits
Summary: A highly efficient gas-phase DMM synthesis route has been proposed recently by conducting nonoxidative dehydrogenation of methanol over Cu/H beta. Both calcined and reduced forms of Cu/H beta catalysts exhibited activity in DMM formation, with increased selectivity attributed to the evolution of Cu species and changes in the number of Lewis acidic sites.
APPLIED CATALYSIS B-ENVIRONMENTAL
(2021)
Review
Chemistry, Organic
Jiang Wang, Shi Zhuangzhi
Summary: Organoboron compounds serve as important building blocks to generate molecular diversity, and strategies enabling the conversion of readily available hydrocarbons into these compounds through C-H borylation are highly appealing. While significant progress has been made in ortho-selective C-H borylation, achieving meta-/para-selectivity remains challenging. This review provides a comprehensive overview of iridium-catalyzed meta-/para-selective aromatic C-H borylation, categorized into directed and non-directed approaches.
CHINESE JOURNAL OF ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Multidisciplinary
Zhengwei Ding, Zhi Liu, Zhijun Wang, Tao Yu, Ming Xu, Jingru Wen, Kaiyan Yang, Hailong Zhang, Liang Xu, Pengfei Li
Summary: This study reports an economical reaction using commercial diboron(4) as a catalyst. By designing a catalytic cycle and using a pyridine cocatalyst, boronyl radicals can be generated and transferred reversibly. The reaction features metal-free conditions, inexpensive and stable catalysts, simple operation, and a broad substrate scope compared to transition metal-based catalysts.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2022)
Article
Chemistry, Multidisciplinary
Md Emdadul Hoque, Ranjana Bisht, Anju Unnikrishnan, Sayan Dey, Mirja Md Mahamudul Hassan, Saikat Guria, Rama Nand Rai, Raghavan B. Sunoj, Buddhadeb Chattopadhyay
Summary: A method of para-selective borylation of aromatic amides is described using a newly designed ligand framework (defa), which shows excellent selectivity and reactivity for the para position. This method can contribute to the development of new catalytic systems and the synthesis of para-functionalized compounds.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Multidisciplinary Sciences
Hui Cao, Qiang Cheng, Armido Studer
Summary: This article introduces a highly selective method for functionalization of pyridines at the meta position, achieving trifluoromethylation, perfluoroalkylation, chlorination, bromination, iodination, nitration, sulfanylation, and selenylation through a dearomatization-rearomatization process. The method can be applied for late-stage functionalization of drugs.
Article
Chemistry, Multidisciplinary
Ping Zhang, Wenju Chang, Hongyun Jiao, Yanshang Kang, Wenxuan Zhao, Peipei Cui, Yong Liang, Wei-Yin Sun, Yi Lu
Summary: The study established a successful electron-deficient catalyzed annulation of N-pentafluorophenylbenzamides with internal alkynes, aided by Lewis acid silver salt, exhibiting a broad tolerance for different substituents on aromatic rings or alkyl-substituted alkynes in the catalytic system.
CHINESE CHEMICAL LETTERS
(2021)
Review
Chemistry, Multidisciplinary
Yoshiaki Nakao
Summary: Nitriles are versatile building blocks in organic synthesis, with common reactions including transformations of cyano groups. While the C-CN bond of nitriles is thermodynamically robust and rarely used as a reaction site, metal-catalyzed reactions have shown the potential for activation. These reactions are categorized into those using CN as a leaving group and those utilizing nitriles as a source of CN groups, offering new possibilities for organic synthesis.
Article
Chemistry, Multidisciplinary
Kazuhiko Semba, Naoki Ohta, Fritz Paulus, Masaki Ohata, Yoshiaki Nakao
Summary: This new method allows for allylarylation of electron-deficient alkenes using aryl boronates and allylic carbonates as starting materials, leading to a variety of carbon skeletons. Mechanistic studies reveal that the reaction is facilitated by a cooperative catalysis involving Pd-0/Pd-II redox and Pd-II/Pd-II non-redox catalytic cycles.
CHEMISTRY-A EUROPEAN JOURNAL
(2021)
Article
Chemistry, Multidisciplinary
Naofumi Hara, Konosuke Yamamoto, Yuuki Tanaka, Teruhiko Saito, Shigeyoshi Sakaki, Yoshiaki Nakao
Summary: In this study, rhodium complexes with X-type PBP and PGaP pincer ligands were synthesized, showing that the sigma-donicity and trans-influence of the X-type boryl ligand are stronger than those of the X-type gallyl ligand. The Lewis acidity of the PEP-Rh complexes (E = B, Al, Ga) was examined, with experimental and computational results indicating that the Lewis acidity increases in the order B (1) < Ga < Al.
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN
(2021)
Article
Chemistry, Multidisciplinary
Rin Seki, Naofumi Hara, Teruhiko Saito, Yoshiaki Nakao
Summary: In this study, we reported a novel rhodium catalyst with X-type PAlP pincer ligand for catalytic reduction of a C-O bond and borylation. The reaction mechanism was revealed through characterization of reaction intermediate and deuterium-labeling experiments. This catalytic system demonstrated steric-hindrance-dependent chemoselectivity, providing a new strategy for selective C-O bond activation through heterobimetallic catalysis.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2021)
Article
Chemistry, Organic
Kazuhiko Semba, Yasuhiro Ohtagaki, Yoshiaki Nakao
Summary: A method for 1,2-arylboration of aliphatic alkenes to afford alkylboronic esters through cooperative palladium/copper catalysis was developed, showing high regioselectivity and tolerance to various functional groups under the reaction conditions.
TETRAHEDRON LETTERS
(2021)
Review
Chemistry, Multidisciplinary
Myuto Kashihara, Yoshiaki Nakao
Summary: Cross-coupling reactions using nitroarenes as electrophiles have gained attention due to their ease of accessibility and potential advantages over haloarenes. Recent research has focused on developing new catalyst systems and reaction conditions to improve the efficiency and practicality of these reactions, with promising results in diversifying bond-forming reactions and reducing catalyst loading. Research in this field is expected to continue growing as the utility of nitroarenes in organic synthesis is reevaluated.
ACCOUNTS OF CHEMICAL RESEARCH
(2021)
Article
Chemistry, Inorganic & Nuclear
Naoki Matsushita, Myuto Kashihara, Michele Formica, Yoshiaki Nakao
Summary: Through the use of a new designed ligand, Pd-catalyzed etherification of nitroarenes with arenols was achieved, allowing for the direct access to a range of unsymmetrical diaryl ethers. The design of the ligand facilitated both the oxidative addition and reductive elimination steps of the catalytic cycle, providing mechanistic insights for optimizing the reaction.
Article
Chemistry, Organic
Naofumi Hara, Koki Aso, Qiao-Zhi Li, Shigeyoshi Sakaki, Yoshiaki Nakao
Summary: This study reports a C2-and mono-selective alkylation of various pyridines and azines with unactivated alkenes and vinylarenes using a heterobimetallic Rh-Al catalyst. Experimental results show that the use of aliphatic alkenes exclusively affords linear alkylation products, while vinylarenes mainly afford branched alkylation products. The details of the reaction mechanism, revealed by DFT calculations, indicate that the reductive elimination of the products is rate-determining, consistent with experimental results. The origin of the linear/branched selectivity is elucidated based on deformation/interaction analysis.
Article
Chemistry, Applied
Qiao-Zhi Li, Naofumi Hara, Kazuhiko Semba, Yoshiaki Nakao, Shigeyoshi Sakaki
Summary: Rh(PAlP) is a new type of catalyst for reactions via sigma-bond activation, showing unique Rh-Al direct bond, flexible substrate coordination, and new catalytic functions for C-H and C-F sigma-bond activations. The unusual Rh delta--Al delta+ polarization and coordination flexibility play important roles in these catalytic reactions.
TOPICS IN CATALYSIS
(2022)
Article
Chemistry, Multidisciplinary
Kazuhiko Semba, Fumiya Shimoura, Yoshiaki Nakao
Summary: A cobalt complex ligated with a PAlP pincer ligand was synthesized and the Lewis acidity of the aluminum atom on the cobalt complex was confirmed by coordination with 4-dimethylaminopyridine (DMAP). Reactions of the cobalt complex with H2O, EtOH, i-PrOH, and t-BuOH efficiently yielded the corresponding cobalt hydride complexes.
Article
Chemistry, Physical
Naofumi Hara, Kazuhiko Semba, Yoshiaki Nakao
Summary: Transition metal complexes with X-type aluminyl ligands exhibit strong reactivity and enable various challenging catalytic transformations such as transfer dehydrogenation, highly efficient CO2 reduction, and site-selective C-H bond functionalization.
Article
Chemistry, Organic
Ikuya Fujii, Kazuhiko Semba, Yoshiaki Nakao
Summary: Rhodium-aluminum bimetallic complexes catalyze the Kumada-Tamao-Corriu (KTC) cross-coupling reaction using arylmagnesium compounds generated from corresponding aryl fluorides or chlorides. This method allows the challenging KTC coupling reaction to be carried out using aryl fluorides as nucleophiles, resulting in various biaryls.
Review
Chemistry, Organic
Yoshiaki Nakao
Summary: C-H functionalization is a key technique in organic synthesis to simplify chemical processes by converting unfunctionalized C-H bonds into functional groups. Traditionally, functionalization required pre-functionalized compounds, but now direct transformation is possible. However, current strategies using directing groups and additional steps limit efficiency, while a new approach utilizing Lewis acid-base formations to control site-selectivity of functionalization is being explored.
JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN
(2021)
Article
Chemistry, Multidisciplinary
Naofumi Hara, Nao Uemura, Yoshiaki Nakao
Summary: A C2-selective mono-silylation of various pyridines has been developed using a Rh-Al complex, where the site- and mono-selectivity are controlled by the coordination of pyridine to the Lewis-acidic Al center. A reaction mechanism is proposed based on the isolation of a (2-pyridyl)silylrhodium intermediate from several mechanistic studies.
CHEMICAL COMMUNICATIONS
(2021)
Article
Chemistry, Organic
Kitty K. Asahara, Myuto Kashihara, Kei Muto, Yoshiaki Nakao, Junichiro Yamaguchi
Summary: The activation of Ar-NO2 bonds by Pd/BrettPhos catalyst has enabled denitrative couplings, overcoming the bottleneck of general denitrative transformations. Deep understanding of the reaction mechanism also led to the design of a more active Pd/NHC system.
JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN
(2021)