Article
Chemistry, Applied
Yusuke Oyamada, Shintaro Yamasaki, Mika Tsuzuki, Takumi Kitagawa, Masaru Kondo, Takahiro Sasamori, Shuichi Nakamura
Summary: The catalytic enantioselective allenylation of ketimines derived from isatins is reported. High regio- and enantioselective products were obtained using a bis(imidazoline)-palladium catalyst. The obtained products were further converted into various chiral amines. The stereoselectivity origin was revealed by DFT calculations of the transition state.
ADVANCED SYNTHESIS & CATALYSIS
(2022)
Article
Chemistry, Organic
Pedro P. De Castro, Gabriel M. F. Batista, Giovanni W. Amarante, Helio F. Dos Santos
Summary: Theoretical calculations and control experiments were used to investigate the mechanism and origin of enantioselectivity in the phosphoric-acid-catalyzed dynamic kinetic resolution of azlactones. The results identified a Munchnone intermediate as crucial in the isomerization of azlactone rings, and the developed model successfully predicted enantioselectivity under various reaction conditions.
JOURNAL OF ORGANIC CHEMISTRY
(2021)
Article
Chemistry, Multidisciplinary
Xinyao Li, Johannes Grosskopf, Christian Jandl, Thorsten Bach
Summary: 3-Substituted quinoxalin-2(1H)-ones and various aryl-substituted or tethered olefins can undergo an enantioselective aza Paterno-Buchi reaction upon irradiation with a chiral sensitizer at lambda=420 nm. The absolute and relative configuration of the products were elucidated by X-ray crystallography, suggesting triplet energy transfer in a hydrogen-bonded complex between the imine substrate and the catalyst. Preliminary experiments also explored intramolecular cycloaddition and alternative reaction modes of quinoxalinones.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2021)
Article
Chemistry, Multidisciplinary
Guolin Wu, Yuan Yao, Gen Li, Xue Zhang, Hui Qian, Shengming Ma
Summary: This study developed a catalytic recipe of copper halides to address the issues of side reactions and selectivity in the 1,5-H transfer of alka-1,4-diyn-3-yl amines, providing various allenynes with excellent enantioselectivities. The method was successfully applied to the first highly enantioselective total synthesis of the natural product scorodonin. Mechanistic studies and DFT calculations elucidated the regioselectivity for the observed 1,5-H transfer.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Chemistry, Multidisciplinary
Rajasekar Reddy Annapureddy, Finn Burg, Johannes Gramueller, Tino P. Golub, Christian Merten, Stefan M. Huber, Thorsten Bach
Summary: An enantioselective sulfimidation of 3-thiosubstituted 2-quinolones and 2-pyridones was achieved with a stoichiometric nitrene source and a silver-based catalyst system, producing 21 chiral sulfimides in high yields and with significant enantiomeric excess. The reaction demonstrates high site-selectivity and potential for kinetic resolution of chiral sulfoxides. Mechanistic evidence supports the involvement of a heteroleptic silver complex in the reaction.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2021)
Article
Chemistry, Multidisciplinary
Younghun Kim, Heechan Kim, Jung Bae Son, Michael Filatov, Cheol Ho Choi, Nam Ki Lee, Dongwhan Lee
Summary: We invented dual-emissive single-benzene fluorophores that can emit light at different wavelengths simultaneously. This was achieved by modulating the hydrogen bond acidity to generate two emissive tautomers with excited-state proton transfer pathways. The white light emitted by these fluorophores relies on the delicate balance between the energy and intensity of each tautomer's emission. We also synthesized a fluorinated single-benzene fluorophore with a record high solubility in perfluorocarbon solvents and demonstrated their practical utility in white light-emitting devices and multicolor imaging of perfluorocarbon nanodroplets in live cells.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Multidisciplinary
Yasunori Toda, Toshinobu Korenaga, Ren Obayashi, Jun Kikuchi, Masahiro Terada
Summary: The study demonstrates the dynamic parallel kinetic resolution (DPKR) of an alpha-ferrocenyl cation intermediate in an S(N)1 type substitution reaction catalyzed by a chiral phosphoric acid catalyst, providing efficient access to a ferrocenylethylamine derivative for potential use in metal catalysis. The mechanism of this resolution system was elucidated through control experiments and theoretical studies, revealing the involvement of racemization and the chemo-divergent parallel kinetic resolution of enantiomeric alpha-ferrocenyl cations.
Article
Chemistry, Physical
Liya Dai, Pengyao Xing, Aiyou Hao
Summary: In this study, the aryl-group achiral molecular tweezers were found to effectively include chiral guest molecules via halogen bonding and other noncovalent interactions. Experimental and computational calculations revealed the formation of stable 1:1 host-guest complexes, demonstrating the transfer of chirality to achiral host molecules at the supramolecular level.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Chemistry, Physical
Da Xu, Yu Chang, Yidong Liu, Wenling Qin, Hailong Yan
Summary: This study achieved the enantioselective construction of stable VQM intermediates through organocatalyzed bromination, and revealed the mechanistic details of the two sequential events in VQM-involved reactions. The high potential of VQM as axially chiral synthetic reagents in organic chemistry was demonstrated.
Article
Chemistry, Multidisciplinary
Guanghui Wang, Lulu Li, Yifeng Jiang, Xiaowei Zhao, Xu Ban, Tianju Shao, Yanli Yin, Zhiyong Jiang
Summary: A chiral Bronsted acid catalysed phosphine-mediated deoxygenation protocol has been reported for the synthesis of azaarylethynyl tertiary alcohols and azaaryl-functionalized allenes, which are biologically and synthetically important derivatives. This metal-free method demonstrates high efficiency, excellent enantioselectivities, broad substrate scope, and practicality for the synthesis of deuterated allenes.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Multidisciplinary
Martin Berger, Davide Carboni, Paolo Melchiorre
Summary: The study presents the first catalytic enantioselective conjugate addition of allyl groups to alpha, beta-unsaturated aldehydes, utilizing the visible-light-excitation of chiral iminium ions to activate allyl silanes toward the formation of allylic radicals. This radical mechanism overcomes issues seen in traditional conjugate allylation processes and selectively installs prenyl fragments at the beta-carbon of enals.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2021)
Article
Chemistry, Multidisciplinary
Song-Hee Yeo, Anthony Choi, Sophie Greaves, Anthony J. H. M. Meijer, Ilaria Proietti Silvestri, Iain Coldham
Summary: Highly enantiomerically enriched dihydrohydroquinolines were synthesized from quinoline in two steps. The addition of aryllithiums to quinoline with Boc protection yielded N-Boc-2-aryl-1,2-dihydroquinolines. Electrophilic trapping occurred exclusively at C-4 of the dihydroquinoline, supported by DFT studies. Kinetic resolutions with high enantioselectivities were achieved using lithium lithiation and the diamine sparteine.
CHEMISTRY-A EUROPEAN JOURNAL
(2023)
Article
Multidisciplinary Sciences
Ming Yu Jin, Qianqian Zhen, Dengmengfei Xiao, Guanyu Tao, Xiangyou Xing, Peiyuan Yu, Chen Xu
Summary: Non-covalent pi interactions play a central role in differentiating enantiomeric substrates in a Sharpless asymmetric dihydroxylation (SAD)-based kinetic resolution.
NATURE COMMUNICATIONS
(2022)
Article
Chemistry, Multidisciplinary
Arka Porey, Bhaskar Deb Mondal, Joyram Guin
Summary: Enantioenriched acyclic alpha-substituted beta-hydroxy amides were successfully synthesized via enantioselective acylation of primary alcohol with N-heterocyclic carbene, with enhanced selectivity achieved by using cyclic tertiary amine as base additive. Diastereomeric transition state models were proposed to rationalize the origin of enantioselectivity in the catalytic kinetic resolution process.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2021)
Article
Chemistry, Multidisciplinary
Vijayanath Elakkat, Eskedar Tessema, Chia-Her Lin, Xiaoping Wang, Huan-Cheng Chang, You-Ning Zheng, Yu-Cheng Huang, Zhong-Yun Gurumallappa, Zhong-Yun Zhang, Ka Long A. Chan, Hening A. S. Rahayu, Joseph S. Francisco, Norman Lu
Summary: To understand the effect of non-covalent weak interactions on molecules, we investigated different types of weak interactions in fluorinated chiral zinc complexes, including improper H-bonding, tetrel bonds, and halogen bonds. High resolution neutron diffraction studies revealed elongation and shortening of the methylene carbon-hydrogen bond due to tetrel bonds and improper H-bond interactions, respectively. We demonstrated how multiple weak interactions can cumulatively affect the C-H bond and offset its elongation through formation of an improper H-bond. Non-covalent interaction and electrostatic potential analysis investigations confirmed the nature of these interactions using density functional theory (DFT) and related calculations.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Organic
Audrey Gilbert, Thorsten Bach
Summary: Photochemical cascade (domino) reactions can construct complex molecular architectures through consecutive reactions with high diastereoselectivity.
Article
Chemistry, Multidisciplinary
Helena F. Piedra, Manuel Plaza
Summary: The combination of photochemistry and halogen bonding interactions has been developed as a powerful method for the synthesis of radical intermediates under mild conditions. This reaction has previously been limited to the use of aryl and alkyl halides as precursors, but now a new method has been developed for the formation of highly reactive vinyl radicals through halogen bonding. The reaction is tolerant to a wide range of functional groups, is stereoselective, and has potential for scalability. Mechanistic studies suggest the formation of vinyl and sulfur-centered radicals as intermediates, and computational calculations support the role of a halogen-bonding complex as the initiator of the photochemical transformation. Synthetic applications have been developed to expand the utility of this methodology.
Article
Chemistry, Multidisciplinary
Johannes Grosskopf, Alexandra A. Heidecker, Thorsten Bach
Summary: Racemic 3-substituted oxindoles can be converted into enantiomerically pure or enriched material through photochemical deracemization process. Light energy compensates for the loss of entropy and enables predictable editing of the stereogenic center. The obtained oxindoles are valuable intermediates for further transformations with complete retention at the stereogenic center.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Editorial Material
Chemistry, Organic
Anat Milo, Takashi Ooi, Thorsten Bach
JOURNAL OF ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Organic
Niklas Rauscher, Christian Jandl, Thorsten Bach
Summary: A recent photochemical cascade reaction has been developed to access diastereomeric pentacyclic products that possess the carbon skeleton of prezizane natural products. The minor diastereoisomer, with a 2 beta-Me configuration, was transformed into (+)-prezizaan-15-ol through 12 reaction steps. Similarly, the major diastereoisomer, with a 2 alpha-Me configuration, yielded (+)-jinkohol II in an analogous route and was further oxidized at C13 to yield (+)-jinkoholic acid. Total synthesis of these natural products helped clarify their configurations.
Article
Chemistry, Organic
Johanna Proessdorf, Christian Jandl, Thomas Pickl, Thorsten Bach
Summary: Naturally occurring sesquiterpenes with a protoilludane skeleton are frequently oxygenated at carbon atoms C4 and C8. Boronic acid pinacol esters (BPin) can serve as precursors for hydroxy groups at these positions and synthetic methods have been developed for their preparation. Introduction of a boronate at position C4 was achieved through Cu-catalyzed hydroboration of a photochemically generated cyclobutene precursor, while introduction of BPin at carbon atom C8 was accomplished through a photochemical transformation starting with an alkenyl boronate. Subsequent reactions showed the oxidative transformation of boronates into the respective alcohols.
SYNTHESIS-STUTTGART
(2023)
Article
Chemistry, Physical
Malte Leverenz, Hendrik Brockmann, Andreas Dreuw, Thorsten Bach, Golo Storch
Summary: A strong enantiodivergence was observed in the oxadi-x-methane rearrangement of 2,4cyclohexadienones, ranging from +92% ee to -45% ee. The stereochemical outcome is determined solely by the oxazaborolidine substituents. The change in enantioselectivity is linked to a change in substrate binding, and TDDFT studies in the S1 excited state provided further mechanistic insights.
Article
Chemistry, Multidisciplinary
Johannes Grosskopf, Manuel Plaza, Roger Jan Kutta, Patrick Nuernberger, Thorsten Bach
Summary: 2,5-Diketopiperazines are cyclic dipeptides with a wide range of applications, and their enantioselective preparation can be achieved through photochemical deracemization, allowing for stereochemical editing at a single position while maintaining other stereogenic centers unaffected. The chiral benzophenone catalyst in combination with irradiation at lambda=366 nm enables the establishment of configuration at the stereogenic carbon atom C6 at will.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Multidisciplinary
Lilla Koser, Thorsten Bach
Summary: The first total synthesis of (-)-5-deoxyenterocin has been accomplished, starting from pentane-1,3,5-triol with a linear sequence of 16 steps and an overall yield of 0.2%. Key steps of the synthesis include aldol reactions, hydroxylation reactions, and an intramolecular aldol reaction. Despite attempts, a functionalization reaction at position C5 was unsuccessful.
CHEMISTRY-A EUROPEAN JOURNAL
(2023)
Article
Chemistry, Organic
Daniel P. Schwinger, Thomas Pickl, Thorsten Bach
Summary: Cyclohept-1-ene-1-carbaldehyde undergoes photoinduced E & RARR; Z isomerization at & lambda; =350 nm. The ring strain facilitates various reactions, including Diels-Alder cycloadditions, [3 + 2] cycloadditions, and enereactions. The products obtained are trans-fusedat the cycloheptane core and yield up to 82%. Single crystal X-ray analyses confirm the structure and relative configuration. In the presence of BF3 and 2,3-dimethylbuta-1,3-diene, cyclohept-1-ene-1-carbaldehyde undergoes a stereoselective rearrangement to form a tricyclic ketone (87%).
JOURNAL OF ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Multidisciplinary
Morgane de Robichon, Thilo Kratz, Frederike Beyer, Julian Zuber, Christian Merten, Thorsten Bach
Summary: Substituted bicyclo[1.1.0]butanes add enantioselectively to 2(1H)-quinolones upon irradiation, leading to the formation of products with a chiral bicyclo[2.1.1]hexane skeleton. A two-point hydrogen bond between the quinolone and the template is responsible for stereocontrol in the photocycloaddition reaction. The chiral template can be recovered and reused, and sensitization is a suitable tool for performing the reaction with visible light.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Review
Chemistry, Multidisciplinary
Helena F. Piedra, Carlos Valdes, Manuel Plaza
Summary: The discovery of new activation modes for carbon-centered radicals, such as photoredox chemistry and low-energy light activation of halogen-bonding adducts, has greatly enriched the field of organic chemistry. These strategies offer more efficient and sustainable ways to generate highly reactive intermediates and enable novel synthetic transformations.
Article
Chemistry, Multidisciplinary
Alvaro Valdes-Maqueda, Lucia Lopez, Manuel Plaza, Carlos Valdes
Summary: The synthesis of benzylboronates from boronic acids and N-tosylhydrazones via photochemical homologation is described. The reaction proceeds through photolysis and carboborylation, successfully avoiding the protodeboronation of benzylboronic acid. The methodology is versatile, allowing for reactions with different ligands and substrates, and can be adapted to continuous flow conditions. The synthetic versatility of boronates enables further transformations, expanding their applications.
Article
Chemistry, Multidisciplinary
Helena F. Piedra, Victoria Gebler, Carlos Valdes, Manuel Plaza
Summary: In this study, a facile and general synthetic method for the preparation of novel S-alkenyl and dienyl phosphoro(di)thioates was presented for the first time. Mechanistic investigations revealed that the reactions rely on the photochemical excitation of a halogen-bonding complex and follow a radical-based pathway. This method showed a broad substrate scope and high functional group tolerance, including molecules derived from natural products with potential unknown biological properties. Additionally, an efficient continuous flow protocol was developed for the upscale of these reactions.
