Article
Chemistry, Organic
Zhenwei Wu, Hualing He, Minglei Chen, Linfei Zhu, Weitao Zheng, Yang Cao, Jon C. Antilla
Summary: A new method for the catalytic asymmetric reductive amination of ketones with pinacolborane has been developed, using chiral SPINOL-derived borophosphates as catalysts. Good yields and high enantioselectivities of chiral amine derivatives were achieved under mild reaction conditions. The synthetic applicability of this method has been demonstrated by the asymmetric synthesis of (R)-Fendiline.
Article
Chemistry, Inorganic & Nuclear
Chenjun Guo, Fangcao Zhang, Chong Yu, Yunjie Luo
Summary: Hydroboration of amides using the supported lanthanum benzyl material La(CH2C6H4NMe2-o)(3)@SBA-15 is highly active and selective, demonstrating good tolerance for various functional groups and heteroatoms. The reduction procedure showed recyclable and reusable properties of heterogeneous catalysts, and is applicable to gram-scale synthesis. It represents the first example of hydroborative reduction of amides to amines mediated by heterogeneous catalysts.
INORGANIC CHEMISTRY
(2021)
Article
Chemistry, Organic
Gobbilla Sai Kumar, Ravi Kumar, Abhijit Sau, Vadapalli Chandrasekhar, Tarun K. Panda
Summary: Researchers developed a stable iminopyridine-ligated zinc complex that effectively catalyzes the hydroboration of esters and nitriles under solvent-free conditions. Various esters and nitriles with different functionalities were selectively reduced to form corresponding alcohols and amines with good yields. Detailed Hammett plots were provided to explain the electronic effects on the phenyl ring.
JOURNAL OF ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Inorganic & Nuclear
Chong Yu, Chenjun Guo, Linhong Jiang, Mingliang Gong, Yunjie Luo
Summary: The deoxygenative reduction of amides using pinacolborane (HBpin) in the presence of a catalytic amount of Ca[N(SiMe3)(2)](2)(THF)(2) is an efficient method to access amines, with good tolerance to functional groups and heteroatoms. The proposed reaction mechanism provides insight into this transformation.
Article
Chemistry, Multidisciplinary
Yuncong Luo, Shengjie Jiang, Xin Xu
Summary: This work reports a novel site-selective C-H borylation reaction of pyridines at the ortho-position using a yttrocene catalyst, enabling the introduction of boronate groups. The resulting boronates exhibit a broad substrate scope and high atom efficiency, and can undergo various transformations.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Chemistry, Inorganic & Nuclear
Qian Gao, Yu-Hang Li, De-Zhan Chen, Jian-Biao Liu
Summary: A study investigated the detailed catalyst activation process and reaction mechanisms for the deoxygenative reduction of amides with pinacolborane catalyzed by Y[N(TMS)(2)](3) and La[N(TMS)(2)](3) complexes, as well as a La-4(O)acac(10) cluster. The M(III)-hemiaminal complex was found to be the active catalyst for all three. The reaction proceeds through a ligand-centered hydride transfer mechanism, involving the formation of B-O bond, hydride transfer to B, C-O cleavage, hydride transfer to C, and sigma-bond metathesis.
INORGANIC CHEMISTRY
(2023)
Article
Chemistry, Inorganic & Nuclear
Marina Uzelac, Kang Yuan, Gary S. Nichol, Michael J. Ingleson
Summary: Amido-zincates containing hydrides are a promising yet underexplored class of complexes. Synthesis attempts through Zn-C/H-BPin exchange resulted in preferential formation of amide-BPin or (amide-BPin(Y)](-) species, highlighting the need for further research on more selective zincate exchange reactions utilizing amido-organozincates.
DALTON TRANSACTIONS
(2021)
Article
Chemistry, Physical
Cai-Qin Li, Geng Leng, Weiyi Li
Summary: In this study, density functional theory (DFT) calculations were used to investigate the catalytic viability of various aluminum hydrides (AlH) in the hydroboration of CO2. The calculations showed that the AlH species could reduce CO2 to formate. The neutral and cationic AlH species with a tetrahedral structure and lower coordination number were found to be more suitable for the transmetalation process with pinacolborane, allowing for smooth hydride transfer and less geometric deformation. Mechanistic studies and turnover frequency (TOF) analysis identified two promising three-coordinated cationic AlH species as efficient and selective catalysts in the reduction of CO2 with pinacolborane.
CATALYSIS SCIENCE & TECHNOLOGY
(2022)
Article
Biochemistry & Molecular Biology
Miaomiao Zhang, Hongmei Jiao, Haojie Ma, Ran Li, Bo Han, Yuqi Zhang, Jijiang Wang
Summary: A convenient method for the synthesis of alcohols using zinc catalysis has been reported. It does not require acid or base hydrolysis reagents and has high selectivity and scalability, as well as tolerance towards sensitive functionalities.
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
(2022)
Article
Chemistry, Organic
Vinothkumar Vinayagam, Tanguturi Venkatanarayana Hajay Kumar, Ravi Nune, Satish Kumar Karre, Subir Kumar Sadhukhan
Summary: We developed a one-step procedure for selectively reducing secondary and tert-amides to their corresponding amine derivatives in the presence of an ester. This reaction was achieved by combining photoredox, nickel catalysis, and phenyl silane as a reductant under blue LED light (455 nm) at room temperature. Furthermore, this mild light-promoted dual metallaphotoredox catalytic system was effective in selectively reducing lactam to cyclic amines without affecting the ester moiety.
JOURNAL OF ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Organic
Dawei Gong, Degong Kong, Yufei Li, Caiyu Gao, Lina Zhao
Summary: A nickel-catalyzed semihydrogenation of azoarenes to hydrazoarenes with NH3BH3 is developed, exhibiting good functional group tolerance and a high turnover frequency at room temperature. Control and deuterium-labeling experiments reveal that the ethanol hydroxyl and BH3 groups each donated one hydrogen, resulting in the formation of B-(OEt)(3) and H-2 as main byproducts. Density functional theory calculations suggest a ligand-to-ligand hydrogen transfer mechanism for the reaction. This study presents a novel nickel catalytic system for the semihydrogenation of azoarenes.
Article
Chemistry, Multidisciplinary
Fangcao Zhang, Mingliang Gong, Hongzhen Xie, Yunjie Luo
Summary: La(CH2C6H4NMe2-o)(3), a simple and easily accessible lanthanide complex, can serve as a highly efficient catalyst for the reduction of esters to alcohols. This protocol shows good tolerance for various functional groups and relies on a lanthanum hydride species to facilitate the interaction between esters and pinacolborane.
NEW JOURNAL OF CHEMISTRY
(2021)
Article
Chemistry, Organic
Xiang Ren, Zhan Lu
Summary: A series of new 8-OIQ cobalt complexes were synthesized and used for cobalt-catalyzed 1,4-hydroboration of enones with HBpin to access chiral beta,beta-disubstituted ketones with good to excellent selectivities. The protocol is operationally simple and has a broad substrate scope.
Article
Chemistry, Organic
Vaibhav B. Patil, Sandip B. Jadhav, Jagadeesh Babu Nanubolu, Rambabu Chegondi
Summary: In this study, a CuH-catalyzed asymmetric desymmetrization reaction of prochiral cyclopentane-1,3-diones was reported. By using PMHS as a cost-effective hydride source, cyclic 3-hydroxy ketones with an all-carbon quaternary center could be synthesized with high diastereoselectivity. The reaction demonstrated excellent functional group tolerance, including reducible alkyne, alkene, and ester groups, and showed a broad substrate scope. The importance of chiral cyclic 3-hydroxy ketone building blocks was further demonstrated through the synthesis of (-)-estrone, the toxicodenane E core, and fused indoles.
Article
Chemistry, Organic
David M. Fialho, Elham Etemadi-Davan, Olivia C. Langner, Balaram S. Takale, Amol Gadakh, Ganesh Sambasivam, Bruce H. Lipshutz
Summary: Enantioselective syntheses of nonracemic secondary alcohols have been achieved in an aqueous micellar medium via copper-catalyzed reduction of aryl/heteroaryl ketones. This method provides a green protocol to access enantio-enriched alcohols under mild conditions, yielding secondary alcohol products with good to excellent yields and ee values greater than 90%.
Article
Chemistry, Multidisciplinary
Andre Maehringer, Matthias Hennemann, Timothy Clark, Thomas Bein, Dana D. Medina
Summary: This study presents a unique nanoscale material that enables efficient oil-water separation driven by gravity, with high water flux and water adsorption capacity. Furthermore, the material exhibits high separation efficiency for various liquids, particularly in treating water pollutants such as crude oil.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2021)
Article
Chemistry, Multidisciplinary
Patrick M. McCosker, Nicholas M. Butler, Alireza Shakoori, Michel K. Volland, Matthew J. Perry, Jesse W. Mullen, Anthony C. Willis, Timothy Clark, John B. Bremner, Dirk M. Guldi, Paul A. Keller
Summary: In this study, structurally diverse heterocycles were synthesized via cascade reactions of indigo with propargylic electrophiles, enabling chemical space exploration. It was found that the unsaturated propargyl moiety can act as an electrophile when aromatic terminal substitutions are made, competing with leaving group substitution to produce new outcomes. The products from these reactions were investigated for their absorption and fluorescence properties, revealing polarity dependent excited state relaxation pathways and highlighting these reactions as a rapid means to access diverse functional materials.
CHEMISTRY-A EUROPEAN JOURNAL
(2021)
Article
Chemistry, Medicinal
Corinna G. Weinhart, David Wifling, Maximilian F. Schmidt, Eduard Neu, Carina Hoering, Timothy Clark, Peter Gmeiner, Max Keller
Summary: The family of human muscarinic acetylcholine receptors (MRs) lack subtype selective MR ligands due to high sequence homology among the five subtypes (M1R-M5R). A series of M2R ligands containing a dibenzodiazepinone pharmacophore linked to small basic peptides were synthesized, showing that the linker moiety and basic peptide structure play crucial roles in determining M2R affinity and selectivity. The most M2R selective compound exhibited picomolar M2R affinity with high selectivity ratios compared to other M2R preferring MR ligands.
EUROPEAN JOURNAL OF MEDICINAL CHEMISTRY
(2021)
Article
Chemistry, Organic
Jayden J. Gaston, Andrew J. Tague, Jamie E. Smyth, Nicholas M. Butler, Anthony C. Willis, Nico van Eikema Hommes, Haibo Yu, Timothy Clark, Paul A. Keller
Summary: The deprotection of chiral 1,2-bis(tosylamides) to their corresponding 1,2-diamines is mostly unsuccessful under standard conditions. However, a new methodology using Mg/MeOH with steric additions allows the facile synthesis of 1,2-diamines in 78-98% yields. These results are rationalized through density functional theory and the examination of inner and outer-sphere reduction mechanisms.
JOURNAL OF ORGANIC CHEMISTRY
(2021)
Article
Chemistry, Multidisciplinary
Wiebke Alex, Patrick Lorenz, Christian Henkel, Timothy Clark, Andreas Hirsch, Dirk M. Guldi
Summary: This study provides a detailed understanding of the full reaction coordinate of NBDs to QCs and reveals that the photoreversibility of NBDs is influenced by the charge-transfer character.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2022)
Article
Chemistry, Multidisciplinary
Christoph M. Schuesslbauer, Marcel Krug, Tobias Ullrich, Hannah M. Franklin, Steven Stevenson, Timothy Clark, Dirk M. Guldi
Summary: This study reports the photophysical characterization of empty-caged, tubular fullerenes D-5h-C-90 and D-5d-C-100 and compares their properties. It found that D-5d-C-100 has a larger optical band gap and luminesces at room temperature, while D-5h-C-90 does not luminesce. The study also discovered that D-5d-C-100 undergoes hole transfer with electron-donating triethylamines but not electron transfer with electron-accepting methyl viologens.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2022)
Article
Chemistry, Physical
Matthias Hennemann, Timothy Clark
Summary: A modified neglect of differential overlap theory was used to parameterize water and its oligomers, with the addition of polarization functions, Feynman dispersion, and a slight modification of hydrogen nucleus treatment. The results demonstrated the feasibility of obtaining accurate geometries and energies for hydrogen-bonded water aggregates.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Medicinal
Jacqueline C. Calderon, Passainte Ibrahim, Dorothea Gobbo, Francesco Luigi Gervasio, Timothy Clark
Summary: We propose a metadynamics protocol to characterize the activation free-energy profiles of G-protein coupled receptors, focusing on the 5HT1A-receptor as a proof-of-principle study. By using the A100 activation index based on inter-helix distances, we perform metadynamics simulations and obtain free-energy profiles for the receptor in various complexes. Our results not only agree with previous experimental and computational data, but also provide detailed insights into the differences between active and inactive conformations and the role of microswitches in the activation mechanism.
JOURNAL OF CHEMICAL INFORMATION AND MODELING
(2023)
Article
Chemistry, Multidisciplinary
Henrik Gotfredsen, Dominik Thiel, Phillip M. Greibel, Lan Chen, Marcel Krug, Ilias Papadopoulos, Michael J. Ferguson, Mogens Brondsted Nielsen, Tomas Torres, Timothy Clark, Dirk M. Guldi, Rik R. Tykwinski
Summary: This study investigates the influence of sensitizer-chromophore geometry on the separation of singlet excited states into triplet excited states. Two conjugates with different arrangements were synthesized and compared. The results show that the energy transfer rate is 26 times faster in the peripheral arrangement, even though the chromophores are farther apart. This rate acceleration is attributed to the more favorable relative orientation of the transition dipole moments in the peripheral structure. These findings are of significant importance for solar energy research.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Multidisciplinary
Yifan Bo, Yuxuan Hou, Dominik Thiel, Renee Weiss, Timothy Clark, Michael J. Ferguson, Rik R. Tykwinski, Dirk M. Guldi
Summary: This study designs two tetracene dimers with different linking modes, and characterizes the interplay between intramolecular singlet fission (intra-SF) and intramolecular triplet-triplet annihilation up-conversion (intra-TTA-UC) through steady-state and time-resolved absorption and fluorescence spectroscopy. By using Pd-phthalocyanine as a sensitizer, intra-TTA-UC is achieved in the two dimers via indirect photoexcitation in the near-infrared part of the solar spectrum. Temperature-dependent measurements reveal the impact of thermal effects on intra-SF and intra-TTA-UC in different dimers.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Organic
Jacqueline C. Calderon, Alberto Herrera, Frank W. Heinemann, Jens Langer, Anthony Linden, Ahmed Chelouan, Alexander Grasruck, Rafael Anez, Timothy Clark, Romano Dorta
Summary: The inversion barriers Delta G double dagger for planar chiral phosphine-alkene and sulfonamide-alkene hybrid ligands based on phenyl-dibenz-[b,f]-azepine have been determined by density-functional theory calculations. Analysis of the structural and electronic characteristics of the minima and transition states explains the magnitudes of Delta G double dagger and the geometrical changes during the inversion process. The steric repulsion caused by bulky substituents attached to the azepine nitrogen atom has a pronounced effect on the Delta G double dagger value, explaining the stereochemical stability of the ligands.
JOURNAL OF ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Multidisciplinary
Wiebke Zika, Andreas Hirsch, Rene Weiss, Simone Pinter, Christoph M. Schuesslbauer, Timothy Clark, Andreas Hirsch, Dirk M. Guldi
Summary: This study investigates the interconversion between QC and NBD and their application in energy storage through photo-assays. An oxidative electron transfer is observed during the QC-to-NBD isomerization using transient absorption spectroscopy. The complementary use of time-resolved and steady-state spectroscopies allows for a complete description of the photoisomerization reaction of NBDs.
Article
Chemistry, Physical
Timothy Clark, Peter Politzer, Jane S. Murray
Summary: This article addresses the long-standing controversy over the physical origin of covalent bonding, concluding that both a lowering of potential energy and a lowering of kinetic energy contribute to bond formation. Using the virial theorem and analyzing changes in potential and kinetic energy as atoms approach each other, it is found that at large separations, kinetic energy decreases while potential energy increases. However, as atoms approach their equilibrium separation, these changes rapidly reverse, resulting in a net positive kinetic energy and net negative potential energy at equilibrium. Ultimately, bonding at equilibrium is solely determined by the potential energy and is electrostatic in nature.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
Article
Chemistry, Multidisciplinary
Ilias Papadopoulos, David Gutierrez-Moreno, Yifan Bo, Ruben Casillas, Phillip M. Greissel, Timothy Clark, Fernando Fernandez-Lazaro, Dirk M. Guldi
Summary: In this study, a series of phenylene- and naphthalene-linked dimers were designed and synthesized to investigate the inherent differences in monoimide and diimide perylenes and their impact on singlet fission. The results showed that using naphthalene spacers improves the triplet quantum yield and singlet fission performance of both monoimide and diimide perylene derivatives.
Article
Chemistry, Physical
Peter Politzer, Jane S. Murray, Timothy Clark
Summary: It is found that within molecules, π-holes typically display positive electrostatic potentials and polarizing attractive forces with negative sites, resulting from low electronic density regions perpendicular to planar portions of molecular frameworks. Interaction energies of π-hole complexes can be well expressed in terms of regression relationships involving both electrostatics and polarization, exhibiting a range from weak to strong forces. Trend also shows gradual changes in intermolecular separations, van der Waals radii, and configurations of π-hole atoms, indicating a continuum of chemical interactions from weak to strong.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2021)
