Article
Chemistry, Physical
Tobias Taeufer, Richy Hauptmann, Firas El-Hage, Thea S. Mayer, Haijun Jiao, Jabor Rabeah, Jola Pospech
Summary: The study demonstrates the applicability of a heteroaromatic photoredox catalyst in an additive-free photo-mediated hydroamination of stilbenes. Initiated by an organic pyrimidopteridine catalyst, the synthesis of various alpha-phenyl phenethylamine derivatives was achieved, with the stereogenic center of alpha-chiral amines fully preserved. Both starting materials serve as competent quenching partners in the reaction mechanism, as indicated by fluorescence-quenching experiments and spectroscopic analysis.
Article
Multidisciplinary Sciences
Shuaishuai Wang, Tingrui Li, Chengyihan Gu, Jie Han, Chuan-Gang Zhao, Chengjian Zhu, Hairen Tan, Jin Xie
Summary: This article reports on an iron-catalyzed reaction for efficient construction of aromatic tertiary amines, which is important in drug discovery and organic chemistry. The reaction employs a radical tandem C-N coupling strategy and can synthesize nonsymmetric aromatic tertiary amines under mild conditions.
NATURE COMMUNICATIONS
(2022)
Article
Chemistry, Applied
Tongtong Zheng, Zhe Feng, Jun-An Ma, Chi Wai Cheung
Summary: We describe a cascade transformation of nitroarenes and trimethylamine using dual nickel/photoredox catalysis, leading to the synthesis of N-formyl N,N'-diaryl ethylenediamines. The reaction involves multiple C-N and C-C coupling events based on nitrogen and α-aminomethyl radicals derived from the starting materials. The obtained products can further undergo hydrolysis for further derivatizations.
ADVANCED SYNTHESIS & CATALYSIS
(2023)
Article
Chemistry, Multidisciplinary
Lanfeng Wei, Yu Wei, Jinli Zhang, Liang Xu
Summary: This research explores a visible-light-induced oxidative dehydrogenative process using an organoboron compound as the photocatalyst and molecular oxygen as the sole oxidant. This approach successfully accessed an array of N-heterocycles under metal-free mild conditions, in good to excellent yields.
Article
Chemistry, Analytical
Qiu-Yue Cheng, Ting Wang, Jun Hu, Hong-Yuan Chen, Jing-Juan Xu
Summary: Visible-light-mediated heterogeneous photocatalysis is a promising method for organic transformations. However, accurately detecting and identifying photogenerated species, especially short-lived radical intermediates, remains challenging. In this work, a hybrid ion emitter integrated with a pico-liter heterogeneous photocatalytic reactor was developed for the rapid identification of transient radical intermediates produced under visible-light irradiation. This novel coupling device provides a powerful tool for exploring complex heterogeneous photochemical processes and their ultrafast initial transformations.
ANALYTICAL CHEMISTRY
(2023)
Article
Chemistry, Organic
Yaseen Hussain, Deepak Sharma, Tamanna, Pankaj Chauhan
Summary: A novel and highly selective synthesis of pyrrolo[1,2-d][1,4]oxazepin-3(2H)-ones has been achieved using photoredox/N-heterocyclic carbene (NHC) relay catalysis. Various substituted dibenzoxazepines and aryl/hetereoaryl enals were efficiently converted to imines through the organic photoredox catalysis-promoted amine oxidation, followed by a NHC-catalyzed [3 + 2] annulation reaction to afford dibenzoxazepine-fused pyrrolidinones with excellent diastereo- and enantioselectivities.
Article
Chemistry, Organic
Yaseen Hussain, Deepak Sharma, Pankaj Chauhan
Summary: An unprecedented highly stereoselective synthesis of pyrrolo[1,2-d][1,4]oxazepin-3(2H)-ones has been achieved through photoredox/N-heterocyclic carbene (NHC) relay catalysis. Substituted dibenzoxazepines and aryl/heteroaryl enals were successfully converted to dibenzoxazepine-fused pyrrolidinones with excellent diastereo- and enantioselectivities via amine oxidation and [3 + 2] annulation reactions catalyzed by organic photoredox catalysis and NHC, respectively.
Article
Chemistry, Multidisciplinary
Yu Harabuchi, Hiroki Hayashi, Hideaki Takano, Tsuyoshi Mita, Satoshi Maeda
Summary: Systematic reaction path exploration revealed the entire mechanism of Knowles's light-promoted catalytic intramolecular hydroamination. This study found that bond formation/cleavage competes with single electron transfer and that reduction and proton shuttle processes proceed concertedly.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Organic
Aleksi Sahari, Jukka Puumi, Jere K. Mannisto, Timo Repo
Summary: We report the utilization of dual nickel photocatalysis for the synthesis of O-aryl carbamates from aryl iodides or bromides, amines, and carbon dioxide. This reaction occurs under visible light, ambient carbon dioxide pressure, and without the need for stoichiometric activating reagents. The photocatalyst generates the active species, consistent with a Ni(I-III) cycle. The rate-limiting steps are the reduction of Ni(II) to Ni(I) and the subsequent oxidative addition of the aryl halide. The physical properties of the photocatalyst are crucial for the selective and active formation of O-aryl carbamates over various byproducts. Nine new phthalonitrile photocatalysts were synthesized with properties vital to achieving high selectivity and activity.
JOURNAL OF ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Multidisciplinary
Mingjie Liu, Junnan Liu, Jing Li, Zhenghua Zhao, Kai Zhou, Yueming Li, Peipei He, Jiashu Wu, Zongbi Bao, Qiwei Yang, Yiwen Yang, Qilong Ren, Zhiguo Zhang
Summary: This study demonstrates a novel strategy to address the limitations of aryl-ketone photocatalysts in terms of photostability and photoinduced electron transfer applications. By incorporating symmetric aryl ketones into conjugated covalent organic frameworks, improvements in photostability, electronic transfer efficiency, and structure-performance relationships were observed. This system provides a robust rule of thumb for designing new-generation aryl-ketone photocatalysts.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Physical
Jun Zheng, Christoph Nopper, Rifhat Bibi, Ali Nikbakht, Felix Bauer, Bernhard Breit
Summary: A dual photoredox/nickel catalyzed method for the regio- and diastereoselective allylation of N-aryl alpha-amino acids is presented. The reaction provides branched homoallylic amines in high yields and high syn-diastereoselectivity under mild and redox-neutral conditions. The broad substrate scope and high functional group tolerance demonstrate the synthetic flexibility of this reaction.
Article
Multidisciplinary Sciences
Shiwei Lu, Zipeng Wang, Shifa Zhu
Summary: Thiol-yne coupling is a reliable method to connect two molecular units, and this study demonstrates its application in synthesizing diverse macrocycles using gaseous acetylene under photocatalytic conditions. The efficient synthesis of macrocycles is challenging in organic synthesis, but this photocatalyzed thiol-yne click reaction provides a practical route to forge diverse sulfur-containing macrocycles and functionalized molecules.
NATURE COMMUNICATIONS
(2022)
Article
Chemistry, Multidisciplinary
Huanran Miao, Meihui Guan, Tao Xiong, Ge Zhang, Qian Zhang
Summary: In this research, a Co-catalyzed asymmetric hydroamination reaction using commercially accessible secondary amines was developed, allowing for the efficient synthesis of alpha-chiral tertiary amines with good enantioselectivities. Mechanistic studies revealed that the reaction involves CoH-mediated hydrogen atom transfer and a pivotal catalyst-controlled S(N)2-like reaction pathway.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Multidisciplinary
Si-Ming Jia, Yi-Hang Huang, Zhan-Lin Wang, Fang-Xu Fan, Bo-Han Fan, Hao-Xiang Sun, Hao Wang, Fei Wang
Summary: An efficient and highly diastereoselective intermolecular anti-Markovnikov hydroamination of unactivated alkenes with aliphatic azides in the presence of silane is reported. The reaction tolerates a wide range of azides and alkenes, with alkene as the limiting reagent. Mechanistic studies reveal a radical chain pathway, with the use of sterically bulky silane contributing to the excellent diastereoselectivity.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2022)
Article
Chemistry, Multidisciplinary
Yi-Dan Du, Bi-Hong Chen, Wei Shu
Summary: The direct and selective synthesis of primary amines from easily available precursors is challenging but important. This method utilizes ammonium carbonate as an ammonia surrogate to efficiently convert alkenes into primary amines at room temperature, providing a powerful approach for the synthesis of advanced, highly functionalized primary amines.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2021)
Article
Chemistry, Organic
Ruairi O. McCourt, Armido Studer
Summary: A 1,2-difunctionalization reaction of cyclic enol ethers mediated by bis(arylsulfonyl) peroxides is reported. Bis(nosyl) peroxide selectively adds a sulfonyl group at the 3-position of enol ethers, generating an oxocarbenium ion that is trapped by a carboxylic acid nucleophile at the 2-position. The reaction proceeds with good yield and tolerates a variety of cyclic enol ethers as well as different carboxylic acids as the oxocarbenium ion trapping reagents.
JOURNAL OF ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Physical
Yongjing Wang, Kang Ma, Tiantong Zhang, Philipp Alexander Held, Armido Studer, Harald Fuchs, Zhixin Hu, Zhixiang Sun, You Han, Hong-Ying Gao
Summary: The effect of iodine on modulating the self-assembly structures of organic molecules on metal surfaces was systematically studied. By using low-temperature scanning tunneling microscopy and density functional theory, the transformation of molecular self-assembly structures induced by iodine dosing on the Ag(111) surface was explored. It was found that iodine can modulate the self-assembly structure of organic molecules with weak intermolecular interaction, while those with stronger intermolecular hydrogen bonding are not affected. These findings were confirmed by density functional theory calculations.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Chemistry, Multidisciplinary
Niklas Radhoff, Constantin G. G. Daniliuc, Armido Studer
Summary: The design, synthesis, and application of benzene bioisosteres have been a subject of great interest in the past two decades. Recently, bicyclo[2.1.1]hexanes have been established as highly attractive bioisosteres for ortho- and meta-substituted benzenes. In this study, we present a mild, scalable, and transition-metal-free method for constructing highly substituted bicyclo[2.1.1]hexan-2-ones through Lewis acid-catalyzed (3+2)-cycloaddition of bicyclo[1.1.0]-butane ketones with disubstituted ketenes. The reaction exhibits high functional group tolerance, as evidenced by the successful synthesis of various 3-alkyl-3-aryl and 3,3-bisalkyl bicyclo[2.1.1]hexan-2-ones (26 examples, up to 89% yield). Additionally, postfunctionalization of the exocyclic ketone moiety is demonstrated.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Multidisciplinary
Jannik Reimler, Xiao-Ye Yu, Nico Spreckelmeyer, Constantin G. Daniliuc, Armido Studer
Summary: The Friedel-Crafts acylation reaction has been a valuable and versatile reaction, but a new radical approach for the acylation of arenes and heteroarenes is presented in this study. By using cooperative photoredox/NHC radical catalysis, C-H acylation is achieved with regiodivergent outcomes. Aroyl fluorides act as the acylation reagents in both the ionic and radical processes.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
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, Multidisciplinary
Florian Lind, Armido Studer
Summary: Acylsilanes, a class of organosilicon compounds, have been gaining increased attention due to their ability to generate carbenes and their usefulness as reagents in organic synthesis. In this study, a novel and efficient route for the synthesis of acylsilanes was reported through alkene hydrosilylation. By using acylhydrosilanes as silylation reagents in rhodium catalyzed alkene hydrosilylations, a wide range of acylsilanes can be accessed in good to excellent yields under mild conditions with high functional group tolerance and atom economy.
CHEMISTRY-A EUROPEAN JOURNAL
(2023)
Article
Chemistry, Multidisciplinary
Till Drennhaus, Dirk Leifert, Jessika Lammert, Jan Philipp Drennhaus, Klaus Bergander, Constantin G. Daniliuc, Armido Studer
Summary: In this study, enantioenriched chiral indoles were synthesized through a mild and efficient radical cascade reaction using a chiral copper-bisoxazoline complex. The targeted 2-fluoroalkylated 3-(alpha-cyanobenzy-lated) indoles were accessed with excellent enantioselectivity and good yields. Mechanistic studies revealed a negative nonlinear effect which explained the stereochemical outcome. The enantioenriched 3-(alpha-cyanobenzylated) indoles demonstrated scalability and potential utility as hubs for chiral tryptamines, indole-3-acetic acid derivatives, and triarylmethanes, and a formal synthesis of a natural product analogue was disclosed.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Multidisciplinary
Zhe Wang, Nick Wierich, Jingjing Zhang, Constantin G. Daniliuc, Armido Studer
Summary: In this study, a method for direct generation of alkyl radicals from alkylboronic pinacol esters (APEs) through reaction with aminyl radicals is reported. Aminyl radicals are readily generated by visible-light-induced homolytic cleavage of the N-N bond in N-nitrosamines, and C radical generation occurs through nucleohomolytic substitution at boron. As an application, the highly efficient photochemical radical alkyloximation of alkenes with APEs and N-nitrosamines under mild conditions is presented. Various primary, secondary, and tertiary APEs can be used in this scalable transformation.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Physical
Jonas Elfert, Anup Bhunia, Constantin G. Daniliuc, Armido Studer
Summary: In this study, a radical transformation that enables intramolecular oxygen atom transfer to alkenes using the nitro functionality in nitroarenes as an oxygen donor is disclosed. The reaction proceeds via iron-catalyzed metal hydrogen atom transfer to alkenes and subsequent oxygenation, resulting in alkene hydration. Compared to intermolecular radical oxygenation, the intramolecular variant offers advantages, particularly in terms of diastereoselective radical hydration of conformationally flexible alkenes. The aryl moiety connecting the reactive NO2-functionality to the alkene substrate can be cleaved after oxygen transfer, yielding products derived from a formal diastereoselective intermolecular alkene hydration. Additionally, the resulting aniline entity after oxygen transfer can be used for the construction of nitrogen-containing heterocycles.
Article
Chemistry, Multidisciplinary
Hui Cao, Debkanta Bhattacharya, Qiang Cheng, Armido Studer
Summary: Selective C-H functionalization of pyridines is of great value but not well developed. In this study, a redox-neutral dearomatization-rearomatization strategy was used to achieve meta-C-H functionalization of pyridines through oxazino pyridine intermediates. Notably, by switching to acidic conditions, these intermediates underwent highly selective para-functionalization. A broad range of para-alkylated and arylated pyridines were prepared using both radical and ionic pathways. These mild and catalyst-free methods were also applied in the late-stage para-functionalization of drugs. Furthermore, the regioselective meta,para-difunctionalization of pyridines was achieved by exploiting the pH-dependent reactivity of oxazino pyridines.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Multidisciplinary Sciences
Jingjing Zhang, Christian Mueck-Lichtenfeld, Armido Studer
Summary: Chemical activation of water is a hot topic in energy research and enables the conversion of this abundant resource into valuable compounds. In this study, we demonstrate the activation of water using a photocatalytic phosphine-mediated radical process, which involves sequential heterolytic and homolytic cleavage of O-H bonds. The resulting PR3-OH radical intermediate can react with various closed-shell p systems, leading to transfer hydrogenation of the p system and incorporation of hydrogen atoms from water into the product. Experimental and theoretical studies support the importance of the hydrogen atom transfer step in this radical hydrogenation process.
Article
Chemistry, Organic
Shyam Kumar Banjare, Dirk Leifert, Frauke Weidlich, Constantin G. Daniliuc, Fatmah A. Alasmary, Armido Studer
Summary: An oxidative radical cascade addition cyclization approach using eco-friendly iron catalysis and inexpensive tert-butylhydroperoxide (TBHP) as the oxidant has been reported for the synthesis of quinoline-based p-extended polyheterocyclic compounds. This method utilizes readily available ortho-alkynylated aromatic aldehydes as radical precursors and aryl isonitriles as radical acceptors. By applying this approach, quinolines that are p-conjugated with an additional heteroarene moiety can be prepared in a single sequence using indole and thiophene-based carbaldehydes.
Article
Chemistry, Organic
Lena Lezius, Jannik Reimler, Nadine Doeben, Michael Hamm, Constantin G. Daniliuc, Armido Studer
Summary: Cooperative NHC and photoredox catalysis have emerged as an important research field. In this study, a cyclizing aminoacylation of alkenes is achieved through the combination of these two catalytic modes. The key step involves a radical/radical cross-coupling between a persistent ketyl radical and a transient benzylic or aliphatic C-radical, generated through radical cyclization of an oxidatively formed amidyl radical. Various substrates containing an alkene moiety and different acyl fluorides can be used, resulting in moderate to good yields of the products.
Article
Chemistry, Organic
Shyam Kumar Banjare, Dirk Leifert, Frauke Weidlich, Constantin G. Daniliuc, Fatmah A. Alasmary, Armido Studer
Summary: An oxidative radical cascade addition cyclization approach using eco-friendly iron catalysis and inexpensive TBHP as the oxidant has been developed for the synthesis of quinoline-based p-extended polyheterocyclic compounds. This method allows the preparation of quinolines that are p-conjugated with an additional heteroarene moiety in a single sequence.
Article
Chemistry, Multidisciplinary
Anirban Maity, Armido Studer
Summary: 1,2-Aminoxyalkylation of alkenes with alkyl iodides and TEMPONa in the presence of an aryldiazonium salt as an XAT mediator is described. Primary, secondary and tertiary alkyl iodides can serve as C-radical precursors in the 1,2-aminoxyalkylation reaction with electrophilic alkenes. The resulting alkoxyamines can be easily converted to alcohols or ketones through reduction or oxidation, respectively. Mechanistic studies reveal the involvement of aryl radicals generated through SET-reduction of the aryldiazonium salt in the XAT process, allowing the addition of alkyl radicals to alkenes. The trapping of the adduct radicals with TEMPO leads to the formation of 1,2-aminoxyalkylation products. Transition metals are not required for these mild conditions transformations. Direct 1,2-aminoxyperfluoroalkylation of alkenes with perfluoroalkyl halides can be achieved using TEMPONa without the need for an aryldiazonium salt as an XAT mediator.
