Article
Chemistry, Multidisciplinary
Manjur O. Akram, John R. Tidwell, Jason L. Dutton, Caleb D. Martin
Summary: The synthesis of a single site neutral Lewis superacid, tris(ortho-carboranyl)borane (BoCb(3)), was achieved in one pot from commercially available materials. It was confirmed to be a Lewis superacid due to its high fluoride ion affinity (FIA), and exhibited stronger Lewis acidity compared to widely used fluorinated aryl boranes, as evidenced by the Gutmann-Beckett method and adducts with Lewis bases. The unusually high Lewis acidity can be rationalized by the electron-withdrawing effect of ortho-carborane and lack of pi-delocalization of the LUMO. Catalytic studies demonstrated that BoCb(3) is a superior catalyst for promoting C-F bond functionalization reactions compared to tris(pentafluorophenyl)borane [B(C6F5)(3)].
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Chemistry, Organic
Matthias W. Tripp, Daniel Bischof, Maximilian Dreher, Gregor Witte, Ulrich Koert
Summary: F4DNTT and F8DNTT were synthesized through bisthiomethyl alkene intermediates accessible by McMurry coupling or Wittig olefination of partially fluorinated naphthalene precursors. DFT-based calculations, NEXAFS spectroscopy, and UV/Vis measurements were used to analyze the electronic structures of the partially fluorinated DNTTs, revealing reduced exciton binding in thin films.
EUROPEAN JOURNAL OF ORGANIC CHEMISTRY
(2021)
Article
Chemistry, Inorganic & Nuclear
Mukundam Vanga, Alvaro Munoz-Castro, H. V. Rasika Dias
Summary: A useful ligand with three pyridyl donor arms and fluorocarbon substituents surrounding the coordination pocket has been assembled and utilized to stabilize ethylene complexes of copper, silver and gold in coinage metal chemistry.
DALTON TRANSACTIONS
(2022)
Article
Chemistry, Multidisciplinary
Tanja Knuplez, Leon N. Schneider, Tobias Preitschopf, Younes K. J. Bejaoui, Ludwig Zapf, Nils Schopper, Kristina A. M. Maibom, Jan A. P. Sprenger, Franziska Gehrke, Sabine Lorenzen, Roland Graf, Ruediger Bertermann, Ingo Fischer, Nikolai V. Ignat'ev, Maik Finze
Summary: This study presents a scalable and straightforward synthesis method for monofluoro- and difluoromethyl triflates through electrochemical fluorination. The method is also applicable for the preparation of deuterated analogues. The study also provides detailed spectroscopic, structural, and thermal data on (fluoro)methyl and fluoro(ethyl) triflates.
CHEMISTRY-A EUROPEAN JOURNAL
(2023)
Article
Chemistry, Multidisciplinary
Haozhen Wang, Chao Yang, Fangshuai Chen, Gengfeng Zheng, Qing Han
Summary: The TF50-COF catalyst, a partially fluorinated, metal-free, imine-linked two-dimensional triazine covalent organic framework, demonstrates high selectivity and stability in O-2 photoreduction into H2O2. By varying the proportion of fluorine substitution, the catalyst maximizes interlayer interactions, improves crystallinity, accelerates carrier transfer, and enhances photostability. The catalyst achieves a high H2O2 yield rate of 1739 mu mol h(-1) g(-1) and an apparent quantum efficiency of 5.1 % at 400 nm, surpassing the performance of previously reported nonmetal COF-based photocatalysts.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Chemistry, Inorganic & Nuclear
Yongliang Wei, Xiaowen Yang, Minghui Tian, Xue Wang, Tongdao Wang
Summary: The coordination of the B-H bond to a transition metal is of fundamental interest due to its relevance to the transition metal-mediated B-H bond activation mechanism and catalysis. While most reported examples involve sigma-borane/borate complexes with one or two sigma-B-H bonds, compounds with three such bonds are much less common. This study presents a facile synthesis approach for rare transition metal tris(sigma-B-H) borate complexes by salt elimination using [Cp*RuCl](4) and lithium trihydroborates Li[ArBH3] with 2,6-disubstituted aryl groups. These complexes exhibit remarkable thermal stability in solution and feature the unusual sigma-complex with three labile sigma-B-H bonds.
DALTON TRANSACTIONS
(2022)
Article
Chemistry, Multidisciplinary
Ryo Oshimizu, Naoki Ando, Shigehiro Yamaguchi
Summary: In this study, the weak interaction between olefin-borane pi-complexes and frustrated Lewis pairs (FLP) was utilized to modulate the electronic properties of boron-based pi-electron materials. By adding Lewis bases, FLP-type addition reactions occurred, leading to significant changes in the absorption and emission properties of the fluorophores. These findings offer a design strategy for stimuli-responsive emissive boron-based materials.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Chemistry, Physical
Valeria Nori, Fabio Pesciaioli, Arianna Sinibaldi, Giuliana Giorgianni, Armando Carlone
Summary: Boron-based catalysis has gained significant attention in organic synthesis. The use of halogenated triarylboranes as main group Lewis acid catalysts is an appealing strategy, and it has been increasingly employed in various transformations, often performing on par or even better than the gold standard catalysts.
Article
Materials Science, Composites
Xin Wang, Linman Li, Shuyan Liu, Zhuang Nie, Weimiao Wang, Xiangyang Liu, Xu Wang
Summary: This study focuses on modifying the surface of metallic aluminum powders to enhance their interaction with polyimide films, leading to improved thermal conductivity and mechanical strength. The core-shell structure formed after surface modification provides a promising strategy for the development of high-performance flexible electronic devices.
COMPOSITES SCIENCE AND TECHNOLOGY
(2023)
Article
Chemistry, Multidisciplinary
Yun Dai, Wei Meng, Xiangqing Feng, Haifeng Du
Summary: This study demonstrated the metal-free asymmetric hydrogenation of 3-fluorinated chromones using achiral borane and chiral oxazoline as an FLP catalyst, resulting in the synthesis of a variety of optically active 3-fluorochroman-4-ones with high yields of up to 88% ee.
CHEMICAL COMMUNICATIONS
(2022)
Article
Green & Sustainable Science & Technology
Gengshu You, Le Liu, Jin Wang, Min Zhao, Chengjie Zhao, Xu Cai, Jin Tang, Fushen Lu, Tonggang Jiu
Summary: Polythiophene-acid-based conjugated polyelectrolytes have shown promising potential as hole-transport materials for inverted planar perovskite devices. A simple and effective strategy involving tris(pentafluorophenyl)borane as a Lewis acid has been developed to regulate the aggregation of the polyelectrolytes, leading to improved efficiency of perovskite solar cells.
ADVANCED SUSTAINABLE SYSTEMS
(2021)
Article
Materials Science, Ceramics
Zhiguang Wang, Min Ge, Xueli Qi, Shouquan Yu, Hao Zhang, Ru Li, Hao Lan, Weigang Zhang
Summary: In order to investigate the structural evolution of tris(methylamino)borane during the thermal-treating process, polymeric green fiber is cured and treated in different temperatures. The composition and structure of volatile compounds and residual products are analyzed during the pyrolysis process. It is found that oxygen can be used to rapidly cure the fiber while maintaining its tensile strength. The evolution of molecular structure during the pyrolysis process is determined.
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
(2023)
Article
Chemistry, Multidisciplinary
Jan-Henrik Weddeling, Paul Lukas Waltersmann, Beate Neumann, Hans-Georg Stammler, Norbert W. Mitzel
Summary: Synthesizing rigid benzenes with different fluorination patterns and analyzing their packing behavior in solid-state structures, it was found that intermolecular interactions can influence properties of co-crystal structures, such as melting points.
Article
Chemistry, Inorganic & Nuclear
Musa Erdogan, Sevil Ozkinali, Humeyra Mert
Summary: A new fluorinated naphthyl-acrylate based monomer was successfully synthesized and characterized, showing promising potential in the field of synthetic polymer chemistry through a series of careful experiments and analyses.
JOURNAL OF FLUORINE CHEMISTRY
(2021)
Article
Chemistry, Physical
Hideyuki Ishihara, Jianhao Huang, Takuya Mochizuki, Manabu Hatano, Kazuaki Ishihara
Summary: A highly enantio- and diastereoselective carbonyl-ene cyclization was developed using chiral Lewis acid-assisted chiral Bronsted acid (LBA) catalysts, demonstrating high selectivity in both standard and tandem reactions. Mechanistic examinations propose a stepwise reaction pathway involving tertiary carbocation intermediates.
Article
Chemistry, Multidisciplinary
Zhi-Yuan Zhao, Ming Cui, Elisabeth Irran, Martin Oestreich
Summary: This study successfully achieved highly enantioselective silylation of 3-substituted 2H-azirines using a copper-catalyzed reaction with a silyl boronic ester as a latent silicon nucleophile. The resulting C-silylated, unprotected (N-H) aziridines were obtained in high yields and with excellent enantioselectivities, and they can be further converted into valuable compounds without significant loss of enantiomeric excess.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Multidisciplinary
Yi Peng, Martin Oestreich
Summary: Opening the ring of cyclic amines by selectively breaking the carbon-nitrogen bond greatly expands the range of available nitrogen-containing structures. However, methods that can directly open secondary amines are limited. This study presents an efficient reductive ring opening of cyclic amines using PhSiH3 under B(C6F5)(3) catalysis, allowing for the transformation of unstrained cyclic amines into acyclic amines in a simple one-step process. Experimental evidence supports a stepwise mechanism involving silylammonium ions and reductive cleavage of carbon-nitrogen bonds.
CHEMISTRY-A EUROPEAN JOURNAL
(2023)
Article
Chemistry, Multidisciplinary
Tao He, Hendrik F. T. Klare, Martin Oestreich
Summary: The method of methylation of various arenes with methanol is disclosed. The reaction is initiated by counteranion-stabilized silylium or arenium ions, which form Meerwein's salt-like oxonium ions with methanol as the active methylating agents. The silylated methyloxonium ions are stronger electrophiles than their protonated congeners, allowing the Friedel-Crafts alkylation to proceed more efficiently and at a lower reaction temperature. The regeneration of these superelectrophiles within the catalytic cycle is accomplished by the addition of a tetraorganosilane additive, that releases a silylium ion through protodesilylation by the Bri nsted acidic Wheland intermediate, thereby acting as a productive proton-into-silylium ion generator. By this method, even the C-H methylation of electronically deactivated aryl halides with methanol is achieved. The protocol is also applicable to nonactivated primary as well as pi-activated benzylic alcohols. Dialkyl ethers are also competent alkylating agents in the presence of the quaternary phenylsilane additive.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Organic
Supriya Rej, Hendrik F. T. Klare, Martin Oestreich
Summary: Geminal alkenes with an aryl and an allenyl group exhibit the structure of [3]dendralenes. The central alkene double bond in these polyenes can react with a silylium ion, initiating a Nazarov cyclization. The resulting ionic intermediate is captured by hydride in the presence of excess hydrosilane. The benzannulated methylenecyclopentene derivatives with a silylalkyl group then undergo silylium-ion regeneration and an unusual endo-selective intramolecular hydrosilylation. This cascade reaction eventually leads to the formation of a silicon-containing bicyclo[3.2.1]octane skeleton.
Review
Chemistry, Organic
Nektarios Kranidiotis-Hisatomi, Martin Oestreich
Summary: Enantioconvergent transition-metal-catalyzed cross-coupling reactions of racemic a-silyl and a-boryl reagents are important for the synthesis of highly enantioenriched a-chiral silanes and boranes. Palladium, nickel, and copper catalysis are used with a-silyl and a-boryl electrophiles. Numerous chiral ligands have extended the scope of this field. This review summarizes the progress made in this rapidly evolving area.
SYNTHESIS-STUTTGART
(2023)
Article
Chemistry, Organic
Avijit Roy, Haopeng Gao, Hendrik F. T. Klare, Martin Oestreich
Summary: The electrophilic silylium ions were used to investigate the intramolecular Friedel-Crafts-type cyclization of aryl tethered 1,1-difluoroalkenes. The preference for electrophilic silylation of the carbon-carbon double bond over vinylic C(sp(2))-F bonds activation initiates the reaction. Subsequent cyclization and hydrodefluorination of the resulting C(sp(3))-F bonds produce the final product in moderate to good yields. Unlike previous reports, the reaction proceeds with perfluorinated tetraphenylborate counteranion under ambient conditions without the need for a carborate counteranion associated with the silylium ion intermediates.
SYNTHESIS-STUTTGART
(2023)
Article
Chemistry, Organic
Lucie Finck, Sarah Dabrowski, Martin Oestreich
Summary: A denitrogenative palladium-catalyzed C(sp(2))-C(sp(2)) cross coupling reaction of aryl-substituted diazenes capped with a trimethylsilyl group and functionalized aryl bromides is described. The use of a PEPPSITM catalyst in the presence of NaOt-Bu enables the activation of the N-aryl-N'-silyldiazene pronucleophile, leading to the loss of dinitrogen and subsequent coupling with the in-situ-formed aryl nucleophile. This methodology provides access to biaryl compounds with various substituents.
SYNTHESIS-STUTTGART
(2023)
Article
Chemistry, Multidisciplinary
Min Zhu, Hua-Jie Jiang, Illia Sharanov, Elisabeth Irran, Martin Oestreich
Summary: A desymmetrizing silylation of aromatic diols is achieved by using List's counteranion directed silylation technique for asymmetric silyl ether formation of phenol derivatives. The enantioselective discrimination of achiral 1,1'-biaryl-2,6-diols is enabled by a silylium-ion-like silicon electrophile generated from an allylic silane paired with an imidodiphosphorimidate (IDPi). The enantioselectivity of the desymmetrization is further improved by a downstream kinetic resolution, converting the monosilylated minor enantiomer into the corresponding bissilylated diol.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Review
Chemistry, Multidisciplinary
Benedikt Wolff, Martin Oestreich
Summary: This Review summarizes the approaches taken to achieve the stereoselective addition of nucleophiles to these fleeting intermediates, including recent advances where non-covalent interactions and chiral counterions are employed to discriminate either side of a trigonal-planar carbenium ion bearing three different substituents.
ISRAEL JOURNAL OF CHEMISTRY
(2023)
Article
Chemistry, Organic
Honghua Zuo, Hendrik F. T. Klare, Martin Oestreich
Summary: A catalytic silylium-ion-promoted intramolecular alkyne carbosilylation reaction is reported, involving electrophilic activation of the C-C triple bond by a silylium ion and maintenance of the catalytic cycle through protodesilylation of an allylsilane reagent. The reaction exhibits exclusive 7-endo-dig selectivity and results in fully substituted vinylsilane derivatives of silylated benzocycloheptenes. Control experiments demonstrate that the catalytically active silylium ion can be regenerated by protodesilylation of the vinylsilane product.
JOURNAL OF ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Organic
Daniel Broesamlen, Martin Oestreich
Summary: A newly developed hept-4-yl-substituted Pybox ligand enables a nickel-catalyzed enantio- and regioconvergent alkylation of regioisomeric mixtures of racemic germylated allylic electrophiles with alkyl nucleophiles, yielding various chiral gamma-germyl alpha-alkyl allylic building blocks with excellent yields and enantioselectivities. The regioconvergence is attributed to the steering effect of the bulky germyl group. The resulting vinyl germanes can be easily halodegermylated without racemization of the allylic stereocenter, providing synthetically valuable gamma-stereogenic vinyl halides.
Article
Chemistry, Organic
Daniel Bro''samlen, Martin Oestreich
Summary: A Ni-H-catalyzed hydroalkylation of vinylsilanes and -germanes as well as allylsilanes with unactivated alkyl iodides is described. In contrast to reactions with styrene or vinyl boronate esters, the addition across the C-C double bond exhibits anti-Markovnikov selectivity, yielding the linear regioisomer. Mechanistic control experiments confirm a radical mechanism, and a competition experiment demonstrates the chemoselectivity favoring the vinyl group over the allyl group.
Article
Chemistry, Organic
Peng-Wei Long, Tao He, Hendrik F. T. Klare, Martin Oestreich
Summary: This Account summarizes the fascinating chemistry of cyclopropyl-stabilized silylium ions, which can be readily obtained from vinyl-cyclopropanes (VCPs). Depending on the nucleophilic partner, these reactive intermediates undergo direct ring opening or ring expansion, leading to the formation of nonclassical alkene-stabilized silylium ions. The latter can also be obtained by gold and proton electrophiles from silicon compounds containing unsaturated C-C bonds. These reaction cascades can be terminated by the formation of C-H or C-C as well as Si-O bonds, revealing the versatility of these complex reactions.
Article
Chemistry, Physical
Min Zhu, Martin Oestreich
Summary: A group-selective monosilylation of silanediols using List's counteranion-directed silylation methodology is described. The enantioselectivity is achieved by generating a silylium-ion-like silicon electrophile from an allylic silane paired with an imidodiphosphorimidate (IDPi), enabling discrimination of the two hydroxy groups attached to the prochiral silicon atom. Furthermore, the enantioselectivity is improved by a subsequent kinetic resolution, resulting in silicon-stereogenic disiloxanes with high enantiocontrol.
Article
Chemistry, Multidisciplinary
Yuanjiu Xiao, Lei Tang, Tong-Tong Xu, Jiang-Yi-Hui Sheng, Zhongyan Zhou, Lei Yue, Guoqiang Wang, Martin Oestreich, Jian-Jun Feng
Summary: A boron Lewis acid-catalyzed intermolecular carboacyloxylation of ynamides with esters is reported, which provides a direct and efficient way to access fully substituted acyclic enol esters. The reaction shows high regio- and Z/E selectivity and is compatible with readily available allylic carbonates. This strategy allows the construction of acyclic beta,beta-disubstituted enol carbonates of amides and can be applied to the synthesis of enantioenriched alpha-quaternary amides.