Article
Chemistry, Multidisciplinary
Remi F. Andre, Alberto Palazzolo, Cyprien Poucin, Francois Ribot, Sophie Carenco
Summary: This study describes the organocatalyzed hydrosilylation reaction of benzaldehyde with phenylsilane using a phosphine as a catalyst. The solvent polarity significantly influenced the activation of phenylsilane, with the highest conversions obtained in acetonitrile and propylene carbonate. The best results were achieved with linear trialkylphosphines as catalysts, and the hydrosilylation products were identified using heteronuclear H-1-Si-29 NMR spectroscopy.
Article
Chemistry, Physical
Anastassia Matviitsuk, Jesse Lee Panger, Scott E. Denmark
Summary: This study reports a chiral selective method for the sulfenofunctionalization of cyclic and (Z)-alkenes, correcting previous findings through experimental results and demonstrating the different behavior of (Z)-alkenes compared to their more established (E)-counterparts.
Article
Chemistry, Multidisciplinary
Danila O. Zakharov, Konstantin Chernichenko, Kristina Sorochkina, Shengjun Yang, Ville-Veikko Telkki, Timo Repo, Vladimir V. Zhivonitko
Summary: In this study, we report the nuclear spin hyperpolarization of various alkenes achieved through alkyne hydrogenations with a metal-free hydroborane catalyst. The specific spin dynamics in catalytic intermediates leads to the hyperpolarization of one hydrogen in the alkene, allowing for advanced characterization of the catalytic process.
CHEMISTRY-A EUROPEAN JOURNAL
(2022)
Article
Chemistry, Multidisciplinary
Qingyu Zhang, Yung-Yin Chan, Muyin Zhang, Ying-Yeung Yeung, Zhihai Ke
Summary: This study presents a proof-of-concept for hypervalent chalcogenonium center dot center dot center dot pi bonding catalysis. A new catalytic strategy using 1,2-oxaselenolium salts as chalcogen bond donors and alkenes as chalcogen bond acceptors is described. The results demonstrate the feasibility of this concept and highlight the significant effect of counter anions on catalysis based on hypervalent chalcogenonium center dot center dot center dot pi bonding interactions.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Review
Chemistry, Applied
Shengshu Liu, Bing-Qian Zhang, Wen-Ying Xiao, Yin-Long Li, Jun Deng
Summary: Heterocycles containing halogen or chalcogen elements are crucial building blocks in natural products and bioactive targets. Catalytic asymmetric functionalization of carbon-carbon unsaturated bonds with halogen or chalcogen electrophiles is an efficient method to obtain chiral heterocyclic backbones.
ADVANCED SYNTHESIS & CATALYSIS
(2022)
Article
Polymer Science
Yuejia Zhu, Yongzhu Hu, Zhenjiang Li, Bo Liu, Yuanyuan Qu, Zhihao Zhang, Tianfo Guo, Yongqiang Li, Luoyu Gao, Kai Guo
Summary: By introducing 3-amino-1,2,4-benzo-thiadiazine-1,1-dioxide (ABTD) as a bidentate H-bond donor and triethylamine (TEA) as a mild Lewis base, successful control of polylactide (PLA) with predictable molecular weights and extremely narrow dispersities was achieved in room temperature solutions.
EUROPEAN POLYMER JOURNAL
(2021)
Article
Chemistry, Physical
Kuldeep Singh, Idan Avigdori, Alexander Kaushansky, Natalia Fridman, Dor Toledano, Mark Gandelman
Summary: Nitrogen Lewis acids (NLAs) have emerged as a powerful tool in strong bond activation and catalysis. This article presents the synthesis and characterization of a new generation of nitrenium-based Lewis acids and demonstrates their efficiency in gram-scale hydrosilylation reactions. Experimental and theoretical studies provide insights into the mechanistic action of nitrenium Lewis acids in reduction-type reactions.
Review
Chemistry, Physical
Hugo Santos, Lucas A. Zeoly, Manoel T. Rodrigues Jr, Fabio S. Fernandes, Ralph C. Gomes, Wanda P. Almeida, Fernando Coelho
Summary: Since its discovery in the late 1960s, the Morita-Baylis-Hillman (MBH) reaction has been a powerful carbon-carbon sigma-bond-forming reaction, producing small polyfunctionalized molecules. Advances in functional catalysts and reaction conditions have been made to improve the reaction rate, substrate scope, and enantioselectivity. This review provides an updated summary of the main improvements in catalytic systems for the MBH reaction over the past decade until nowadays, aiming to inspire further investigations and overcome the remaining challenges of this fascinating transformation.
Article
Chemistry, Multidisciplinary
Nils Ansmann, Deborah Hartmann, Sonja Sailer, Philipp Erdmann, Rezisha Maskey, Marcel Schorpp, Lutz Greb
Summary: In this study, hypercoordinated silicon anions were characterized using a new donor-free polymeric form of Lewis superacidic bis(perchlorocatecholato)silane 1. The results provide insights into the role of silicon hypercoordination in synthesis and catalysis, and suggest pronounced substrate activation.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Chemistry, Organic
Apoorva Malik, Pragati R. Sharma, Rakesh K. Sharma
Summary: We report a class of quaternary ammonium Cinchona-functionalized crown ether-strapped calix[4]-arene phase-transfer catalysts for the efficient enantioselective alpha-alkylation of glycine imines. The catalyst exhibits excellent catalytic performance at 0.1 mol % catalytic loading, affording the desired alpha-alkylated glycinates with 98% yield and 99.9% ee. The catalyst could be recovered and recycled up to 30 test cycles without a significant drop in activity.
JOURNAL OF ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Multidisciplinary
Roberto del Rio-Rodriguez, Matthew T. Westwood, Marina Sicignano, Martin Juhl, Jose A. Fernandez-Salas, Jose Aleman, Andrew D. Smith
Summary: This study combines the photocatalytic generation of alpha-amino radicals with chiral isothiourea derived alpha,beta-unsaturated acyl ammonium intermediates. The reaction proceeds via a [3+2] radical-polar crossover mechanism to generate gamma-lactams with good yields and enantioselectivities. The enantioselective radical conjugate addition was carried out under batch and flow conditions.
CHEMICAL COMMUNICATIONS
(2022)
Article
Chemistry, Multidisciplinary
Robin Weiss, Emmanuel Aubert, Patrick Pale, Victor Mamane
Summary: Chalcogen bonding between telluronium cations and Lewis bases was shown to have impressive catalytic properties in benchmark reactions. The interaction was confirmed through multi-nuclear NMR analysis and DFT calculations, highlighting the potential of telluronium cations as organocatalysts.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2021)
Article
Chemistry, Physical
Qingqing Luo, Zhou Tian, Jie Tang, Jie Wang, Yin Tian, Cheng Peng, Gu Zhan, Bo Han
Summary: The study focuses on the design of bifunctional 4-pyrrolidinopyridines as Lewis base catalysts, which exhibited excellent efficiency and stereoselectivity in asymmetric cycloaddition reactions. The research provides strong support for the construction of chiral spiropyrazolone derivatives.
Article
Chemistry, Organic
Gen-Fa Wen, Rui Zhang, Chu-Yu Zhang, Chao-Shan Da
Summary: This study compares and explores the catalytic efficiencies of structurally similar alpha- and beta-amino acids in an asymmetric aldol transformation. The results show that both types of amino acids achieve high catalytic efficiencies under different optimal conditions, and in some cases, the beta-amino acid even exhibits higher enantioselectivity than the alpha-amino acid.
SYNTHESIS-STUTTGART
(2023)
Article
Chemistry, Organic
William J. Patterson, Kelly Lucas, Vanessa A. Jones, Zhenghua Chen, Kevin Bardelski, Melissa Guarino-Hotz, Cheyenne S. Brindle
Summary: An efficient synthesis of unsymmetrical bisindolylmethanes has been achieved by utilizing triarylmethyl cations as catalysts to facilitate the reaction between N-arylimines and two different indoles. The optimized organocatalyst allows for excellent single addition selectivity with p-nitrophenyl imines, minimizing waste and environmental impact. The reaction tolerates a broad range of imines and indole nucleophiles, producing a variety of unsymmetrical bisindolylmethanes in high yields.
EUROPEAN JOURNAL OF ORGANIC CHEMISTRY
(2021)
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
Benedikt Wolff, Zheng-Wang Qu, Stefan Grimme, Martin Oestreich
Summary: This study presents a method for the enantioselective reduction of simple carbenium ions using cyclohexadienes with a hydridic C-H bond at an asymmetrically substituted carbon atom. Chiral cyclohexadienes are used as dihydrogen surrogates for the transfer hydrogenation of alkenes (styrenes). The reaction mechanism involves the initiation by trityl cation and a delicate intermolecular capture of a carbenium-ion intermediate by the chiral hydride source, resulting in good enantiomeric ratios of the reduction products.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(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, 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.
Review
Chemistry, Organic
Lucie Finck, Martin Oestreich
Summary: This perspective provides an overview of the underexplored chemistry of diazenes and highlights their potential in synthetic transformations. The stability and reactivity of diazenes have been enhanced by using silicon protection. The generation of aryl, diazenyl, and alkyl anionic intermediates under catalytic conditions opens up new synthetic approaches as alternatives to existing methodologies.
JOURNAL OF ORGANIC CHEMISTRY
(2023)
