Article
Chemistry, Multidisciplinary
Oleksandr Kysliak, Helmar Goerls, Robert Kretschmer
Summary: This study presents the synthesis and characterization of a room-temperature-stable compound with two separated two-coordinated gallium(I) centers. The compound displays enhanced reactivity compared to its mononuclear counterpart due to bimetallic cooperativity. Two mechanistic scenarios of the cooperative bond activation have been identified through computational calculations.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2021)
Article
Chemistry, Multidisciplinary
M. Angeles Fuentes, Riccardo Gava, Noam Saper, Erik Romero, Ana Caballero, John F. Hartwig, Pedro J. Perez
Summary: This study reports a dehydrogenative coupling reaction to form N-alkyl amides by reacting amides with C1-C4 hydrocarbons, using tBuOOtBu as oxidant and a copper complex as catalyst. The reactions showed good yields in benzene or supercritical carbon dioxide as solvents. Compared to previous studies on larger alkanes, the reactivity in this amination process correlated with bond dissociation energies.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2021)
Article
Chemistry, Organic
Cui-Lian Zeng, Hao Wang, Di Gao, Zhen Zhang, Dong Ji, Wei He, Cheng-Kou Liu, Zhao Yang, Zheng Fang, Kai Guo
Summary: This study presents a green and gentle Minisci-type reaction method, in which the cross-dehydrogenative coupling of heteroarenes with aliphatic C(sp(3))-H bonds is achieved under visible-light irradiation. This method does not require oxidants or transition metal catalysts, and only the catalytic equivalent of CF3SO2Na and room temperature are needed to ensure an efficient reaction.
Article
Chemistry, Multidisciplinary
Yusuke Kuroda, Kyungho Park, Yuto Shimazaki, Rong-Lin Zhong, Shigeyoshi Sakaki, Yoshiaki Nakao
Summary: Herein, an iridium/aluminum cooperative catalytic system has been reported for the beta-selective C-H borylation of saturated cyclic amines and lactams. An enantioselective variant has also been achieved using chiral aluminum catalysts, resulting in high stereocontrol in the formation of C-B bonds. Computational studies suggest that the formation of a Lewis pair with the substrates is crucial for lowering the energy of the rate-determining reductive elimination step.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Organic
Aditya Paul, Arunava Sengupta, Somnath Yadav
Summary: The visible light-triggered regioselective synthesis of 2-sulfonamidoindoles and other 2-sulfonamido heteroarenes is achieved through an oxidative cross-dehydrogenative coupling reaction. The reaction is catalyzed by eosin-Y and a nitrogen-centered radical is generated, followed by regioselective addition to the heteroarene. The methodology is straightforward and allows for the synthesis of a wide range of compounds.
JOURNAL OF ORGANIC CHEMISTRY
(2022)
Article
Chemistry, Multidisciplinary
Jose M. Gil-Negrete, Eva Hevia
Summary: Over the past decade, s-block metal catalysis has evolved from being a mysterious curiosity to a well-established field towards sustainable synthesis, with earth-abundant metals showing excellent catalytic performance. Bimetallic reagents have attracted widespread interest for providing enhanced reactivities and selectivities, although most efforts have focused on stoichiometric transformations.
Article
Chemistry, Multidisciplinary
Ming Zhang, Qingyang Zhou, Heng Luo, Zi-Lu Tang, Xiufang Xu, Xiao-Chen Wang
Summary: Here, we present a method for C3-selective cyanation of pyridines by a tandem process using an in situ generated dihydropyridine and a cyano electrophile. This method is suitable for late-stage functionalization of pyridine drugs. The success of this method relies on the low reduction potential of the electrophile and effective transfer of the nitrile group. Detailed investigation of the reaction mechanism revealed that a combination of electronic and steric factors determines the regioselectivity of reactions involving C2-substituted pyridines.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Organic
Chao-Jiu Long, Hong-Ping Pu, Ya-Nan Zhao, Yan-Hong He, Zhi Guan
Summary: Researchers developed a new enantioselective oxidative cross-dehydrogenative coupling method by combining photocatalysis and l-/d-proline catalysis. Acyclic benzylic secondary amines were successfully transformed into beta-amino carbonyl compounds with good yields up to 86% and high enantio- and diastereoselectivities (up to 99% ee and > 99 : 1 dr) under mild and oxidant-free conditions. This method has wide substrate scope, excellent functional group tolerance, and simple operation.
ORGANIC CHEMISTRY FRONTIERS
(2023)
Article
Chemistry, Multidisciplinary
Congjun Yu, Raolin Huang, Frederic W. Patureau
Summary: This article introduces a novel non-directed dehydrogenative phenone coupling method between methylarenes and aromatic C_H bonds, which exhibits a broad substrate scope and can be applied for gram-scale synthesis of drug analogues.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Chemistry, Multidisciplinary
Jia-Hao Chen, Ming-Ya Teng, Fan-Rui Huang, Hong Song, Zhen-Kai Wang, He-Lin Zhuang, Yong-Jie Wu, Xu Wu, Qi-Jun Yao, Bing-Feng Shi
Summary: The past decade has seen significant progress in asymmetric C-H activation, although achieving enantioselective C-H alkoxylation and amination with alcohols and free amines has remained challenging. In this study, we report the first enantioselective dehydrogenative C-H alkoxylation and amination using a simple cobalt/salicyloxazoline (Salox) catalyst. By using inexpensive cobalt(II) salts as catalysts and Saloxs as chiral ligands, we have developed an efficient method to access P-stereogenic compounds with excellent enantioselectivities (up to >99% ee). The practicality of this protocol has been demonstrated through gram-scale preparation and further derivatizations of the resulting P-stereogenic phosphinamides, offering a flexible asymmetric alternative to access P-stereogenic mono- and diphosphine chiral ligands. Preliminary mechanistic studies suggest the involvement of a cobalt(III/IV/II) catalytic cycle in the enantioselective C-H alkoxylation reaction.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Chemistry, Organic
Xiao-De An, Da-Ying Shao, Bin Qiu, Jian Xiao
Summary: An unprecedented cross-dehydrogenative coupling reaction of two C(sp(3))-H bonds to form ninemembered rings via hydride transfer has been developed. This methodology offers atom and step economy, metal-free and redox-neutral conditions, and water as the byproduct, making it applicable even with decomposed aldehydes.
Article
Chemistry, Organic
Xiao-De An, Da-Ying Shao, Bin Qiu, Jian Xiao
Summary: An unprecedented hydride transfer-triggered cross-dehydrogenative coupling of two C(sp(3))-H bonds to target nine membered rings has been developed. Salient features of this methodology include atom and step economy and metal-free and redox-neutral conditions, with water as the byproduct and proceeding well even with decomposed aldehydes.
Review
Chemistry, Multidisciplinary
Clement Jacob, Bert U. W. Maes, Gwilherm Evano
Summary: Direct functionalization of C-H bonds is a fundamental transformation in organic synthesis, often relying on directing groups for activation. The development of transient directing groups strategy has revolutionized C-H bond functionalization, allowing for direct and selective introduction of functional groups onto various substrates.
CHEMISTRY-A EUROPEAN JOURNAL
(2021)
Article
Chemistry, Applied
Jun Xu, Wenqiang Xu, Xinhao Zhang, Jie Wu, Pengfei Zhang, Lijuan Song, Xiaogang Liu
Summary: This study demonstrates a divergent and controllable synthesis of quinolones from quinoline scaffolds through sulfonyl chloride-controlled, copper-catalyzed, site-selective radical C-H functionalization/cyclization. The catalytic system shows tolerance to a wide range of functional groups and provides both 2-thioquinolone and 4-quinolone derivatives in moderate to good yields. The mechanism involves single-electron transfer, and the selectivity of the reaction is determined by the steric hindrance and electronic effect of sulfonyl chlorides. This transformation provides a novel example of divergent radical C-H functionalization controlled by small organic molecules and facilitates the rapid derivatization of medicinally important scaffolds for late-stage drug modification.
ADVANCED SYNTHESIS & CATALYSIS
(2023)
Article
Chemistry, Organic
Fang Wang, Qianting Zhou, Xinying Zhang, Xuesen Fan
Summary: A novel and efficient alpha-C(sp(3))-H alkenylation of cyclic amines with maleimides was presented, featuring readily available and structurally diverse substrates, a green and economical catalyst, a unique reaction pathway, mild reaction conditions, high efficiency, and excellent atom economy. This new reaction enriches the application of Fe(III)-catalyzed C(sp(3))-H activation and functionalization.
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)
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.
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)