@article{HuangHuShietal.2022,
  author    = {Huang, Mingming and Hu, Jiefeng and Shi, Shasha and Friedrich, Alexandra and Krebs, Johannes and Westcott, Stephen A. and Radius, Udo and Marder, Todd B.},
  title     = {Selective, Transition Metal-free 1,2-Diboration of Alkyl Halides, Tosylates, and Alcohols},
  series = {Chemistry-A European Journal},
  volume    = {28},
  journal   = {Chemistry-A European Journal},
  number    = {24},
  doi       = {10.1002/chem.202200480},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-318262},
  year      = {2022},
  abstract  = {Defunctionalization of readily available feedstocks to provide alkenes for the synthesis of multifunctional molecules represents an extremely useful process in organic synthesis. Herein, we describe a transition metal-free, simple and efficient strategy to access alkyl 1,2-bis(boronate esters) via regio- and diastereoselective diboration of secondary and tertiary alkyl halides (Br, Cl, I), tosylates, and alcohols. Control experiments demonstrated that the key to this high reactivity and selectivity is the addition of a combination of potassium iodide and N,N-dimethylacetamide (DMA). The practicality and industrial potential of this transformation are demonstrated by its operational simplicity, wide functional group tolerance, and the late-stage modification of complex molecules. From a drug discovery perspective, this synthetic method offers control of the position of diversification and diastereoselectivity in complex ring scaffolds, which would be especially useful in a lead optimization program.},
  language  = {en}
}
@article{HeRauchFriedrichetal.2021,
  author    = {He, Jiang and Rauch, Florian and Friedrich, Alexandra and Krebs, Johannes and Krummenacher, Ivo and Bertermann, R{\"u}diger and Nitsch, J{\"o}rn and Braunschweig, Holger and Finze, Maik and Marder, Todd B.},
  title     = {Phenylpyridyl-fused boroles: a unique coordination mode and weak B-N coordination-induced dual fluorescence},
  series = {Angewandte Chemie International Edition},
  volume    = {60},
  journal   = {Angewandte Chemie International Edition},
  number    = {9},
  doi       = {10.1002/anie.202013692},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256423},
  pages     = {4833-4840},
  year      = {2021},
  abstract  = {Phenylpyridyl-fused boroles [TipPBB1]\(_4\) and TipPBB2 were synthesized and their properties investigated. [TipPBB1]\(_4\) forms a tetramer in both the solid state and solution. TipPBB2 contains a 4-coordinate boron atom in the solid state but dissociates to give a 3-coordinate boron species in solution. TipPBB2 shows interesting temperature-dependent dual fluorescence in solution because of the equilibrium between 3- and 4-coordinate boron species due to weak N⋅⋅⋅B intermolecular coordination.},
  language  = {en}
}
@article{KrebsHaehnelKrummenacheretal.2021,
  author    = {Krebs, Johannes and Haehnel, Martin and Krummenacher, Ivo and Friedrich, Alexandra and Braunschweig, Holger and Finze, Maik and Ji, Lei and Marder, Todd B.},
  title     = {Synthesis and Structure of an o-Carboranyl-Substituted Three-Coordinate Borane Radical Anion},
  series = {Chemistry—A European Journal},
  volume    = {27},
  journal   = {Chemistry—A European Journal},
  number    = {31},
  doi       = {10.1002/chem.202100938},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256841},
  pages     = {8159-8167},
  year      = {2021},
  abstract  = {Bis(1-(4-tolyl)-carboran-2-yl)-(4-tolyl)-borane [(1-(4-MeC\(_{6}\)H\(_{4}\))-closo-1,2-C\(_{2}\)B\(_{10}\)H\(_{10}\)-2-)\(_{2}\)(4-MeC\(_{6}\)H\(_{4}\))B] (1), a new bis(o-carboranyl)-(R)-borane was synthesised by lithiation of the o-carboranyl precursor and subsequent salt metathesis reaction with (4-tolyl)BBr\(_{2}\). Cyclic voltammetry experiments on 1 show multiple distinct reduction events with a one-electron first reduction. In a selective reduction experiment the corresponding paramagnetic radical anion 1\(^{.-}\) was isolated and characterized. Single-crystal structure analyses allow an in-depth comparison of 1, 1\(^{.-}\), their calculated geometries, and the S\(_{1}\) excited state of 1. Photophysical studies of 1 show a charge transfer (CT) emission with low quantum yield in solution but a strong increase in the solid state. TD-DFT calculations were used to identify transition-relevant orbitals.},
  language  = {en}
}
@article{HuangWuKrebsetal.2021,
  author    = {Huang, Mingming and Wu, Zhu and Krebs, Johannes and Friedrich, Alexandra and Luo, Xiaoling and Westcott, Stephen A. and Radius, Udo and Marder, Todd B.},
  title     = {Ni-Catalyzed Borylation of Aryl Sulfoxides},
  series = {Chemistry—A European Journal},
  volume    = {27},
  journal   = {Chemistry—A European Journal},
  number    = {31},
  doi       = {10.1002/chem.202100342},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256778},
  pages     = {8149-8158},
  year      = {2021},
  abstract  = {A nickel/N-heterocyclic carbene (NHC) catalytic system has been developed for the borylation of aryl sulfoxides with B\(_{2}\)(neop)\(_{2}\) (neop=neopentyl glycolato). A wide range of aryl sulfoxides with different electronic and steric properties were converted into the corresponding arylboronic esters in good yields. The regioselective borylation of unsymmetric diaryl sulfoxides was also feasible leading to borylation of the sterically less encumbered aryl substituent. Competition experiments demonstrated that an electron-deficient aryl moiety reacts preferentially. The origin of the selectivity in the Ni-catalyzed borylation of electronically biased unsymmetrical diaryl sulfoxide lies in the oxidative addition step of the catalytic cycle, as oxidative addition of methoxyphenyl 4-(trifluoromethyl)phenyl sulfoxide to the Ni(0) complex occurs selectively to give the structurally characterized complex trans-[Ni(ICy)\(_{2}\)(4-CF\(_{3}\)-C\(_{6}\)H\(_{4}\)){(SO)-4-MeO-C\(_{6}\)H\(_{4}\)}] 4. For complex 5, the isomer trans-[Ni(ICy)\(_{2}\)(C\(_{6}\)H\(_{5}\))(OSC\(_{6}\)H\(_{5}\))] 5-I was structurally characterized in which the phenyl sulfinyl ligand is bound via the oxygen atom to nickel. In solution, the complex trans-[Ni(ICy)\(_{2}\)(C\(_{6}\)H\(_{5}\))(OSC\(_{6}\)H\(_{5}\))] 5-I is in equilibrium with the S-bonded isomer trans-[Ni(ICy)\(_{2}\)(C\(_{6}\)H\(_{5}\))(SOC\(_{6}\)H\(_{5}\))] 5, as shown by NMR spectroscopy. DFT calculations reveal that these isomers are separated by a mere 0.3 kJ/mol (M06/def2-TZVP-level of theory) and connected via a transition state trans-[Ni(ICy)\(_{2}\)(C\(_{6}\)H\(_{5}\))(η\(^{2}\)-{SO}-C\(_{6}\)H\(_{5}\))], which lies only 10.8 kcal/mol above 5.},
  language  = {en}
}
@article{FergerBergerRauchetal.2021,
  author    = {Ferger, Matthias and Berger, Sarina M. and Rauch, Florian and Sch{\"o}nitz, Markus and R{\"u}he, Jessica and Krebs, Johannes and Friedrich, Alexandra and Marder, Todd B.},
  title     = {Synthesis of Highly Functionalizable Symmetrically and Unsymmetrically Substituted Triarylboranes from Bench-Stable Boron Precursors},
  series = {Chemistry—A European Journal},
  volume    = {27},
  journal   = {Chemistry—A European Journal},
  number    = {35},
  doi       = {10.1002/chem.202100632},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256827},
  pages     = {9094-9101},
  year      = {2021},
  abstract  = {A novel and convenient methodology for the one-pot synthesis of sterically congested triarylboranes by using bench-stable aryltrifluoroborates as the boron source is reported. This procedure gives systematic access to symmetrically and unsymmetrically substituted triarylboranes of the types BAr\(_{2}\)Ar' and BArAr'Ar'', respectively. Three unsymmetrically substituted triarylboranes as well as their iridium-catalyzed C-H borylation products are reported. These borylated triarylboranes contain one to three positions that can subsequently be orthogonally functionalized in follow-up reactions, such as Suzuki-Miyaura cross-couplings or Sonogashira couplings.},
  language  = {en}
}
@article{KotlyarKrebsSolimandoetal.2023,
  author    = {Kotlyar, Mischa J. and Krebs, Markus and Solimando, Antonio Giovanni and Marquardt, Andr{\´e} and Burger, Maximilian and K{\"u}bler, Hubert and Bargou, Ralf and Kneitz, Susanne and Otto, Wolfgang and Breyer, Johannes and Vergho, Daniel C. and Kneitz, Burkhard and Kalogirou, Charis},
  title     = {Critical evaluation of a microRNA-based risk classifier predicting cancer-specific survival in renal cell carcinoma with tumor thrombus of the inferior vena cava},
  series = {Cancers},
  volume    = {15},
  journal   = {Cancers},
  number    = {7},
  issn      = {2072-6694},
  doi       = {10.3390/cancers15071981},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-311040},
  year      = {2023},
  abstract  = {(1) Background: Clear cell renal cell carcinoma extending into the inferior vena cava (ccRCC\(^{IVC}\)) represents a clinical high-risk setting. However, there is substantial heterogeneity within this patient subgroup regarding survival outcomes. Previously, members of our group developed a microRNA(miR)-based risk classifier — containing miR-21-5p, miR-126-3p and miR-221-3p expression — which significantly predicted the cancer-specific survival (CSS) of ccRCC\(^{IVC}\) patients. (2) Methods: Examining a single-center cohort of tumor tissue from n = 56 patients with ccRCC\(^{IVC}\), we measured the expression levels of miR-21, miR-126, and miR-221 using qRT-PCR. The prognostic impact of clinicopathological parameters and miR expression were investigated via single-variable and multivariable Cox regression. Referring to the previously established risk classifier, we performed Kaplan-Meier analyses for single miR expression levels and the combined risk classifier. Cut-off values and weights within the risk classifier were taken from the previous study. (3) Results: miR-21 and miR-126 expression were significantly associated with lymphonodal status at the time of surgery, the development of metastasis during follow-up, and cancer-related death. In Kaplan-Meier analyses, miR-21 and miR-126 significantly impacted CSS in our cohort. Moreover, applying the miR-based risk classifier significantly stratified ccRCC\(^{IVC}\) according to CSS. (4) Conclusions: In our retrospective analysis, we successfully validated the miR-based risk classifier within an independent ccRCC\(^{IVC}\) cohort.},
  language  = {en}
}
@phdthesis{Krebs2023,
  author    = {Krebs, Johannes Heinrich},
  title     = {Investigation of Dicarba-closo-dodecaborane as a Substituent on Three-coordinate Boron and as an Acceptor in a Pyrene-Donor-Acceptor System},
  doi       = {10.25972/OPUS-28675},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-286758},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {1. Bis(1-(4-tolyl)-carboran-2-yl)-(4-tolyl)-borane, a new bis(o-carboranyl)-(R)-borane 1 was synthesised by lithiation of the o-carboranyl precursor and subsequent salt metathesis reaction with (4-tolyl)BBr2. Cyclic voltammetry experiments on 1 show multiple distinct reduction events with a one-electron first reduction. In a selective reduction experiment the corresponding paramagnetic radical anion 1•- was isolated and characterized. Single-crystal structure analyses allow an in-depth comparison of 1, 1•-, their calculated geometries, and the S1 excited state of 1. 2. The choice of backbone linker for ortho-bis-(9-borafluorene)s has a great influence on the LUMO located at the boron centers and therefore the reactivity of the respective compounds. Herein, we report the room temperature rearrangement of 1,2-bis-(9-borafluorenyl-)-ortho-carborane, C2B10H10-1,2-[B(C12H8)]2 ([2a]) featuring o-carborane as the inorganic three-dimensional backbone and the synthesis of 1,2-bis-(9-borafluorenyl-)benzene, C6H4-1,2-[B(C12H8)]2 (2b) its phenylene analog. DFT calculations on the transition state for the rearrangement support an intramolecular C-H bond activation process via an SEAr-like mechanism in [2a], and predicted that the same rearrangement would take place in 2b, but at elevated temperatures, which indeed proved to be the case. 3. We synthesized 4 a julolidine-like pyrenyl-o-carborane, with pyrene substituted at the 2,7-positions on the HOMO/LUMO nodal plane, continuing our research. Using solid state molecular structures, photophysical data, cyclic voltammetry, DFT and TD-DFT calculations we compare o-carborane and the B(mes)2 (mes = 2,4,6-Me3C6H2) as acceptor groups and confirm the julolidine-like donor strength.},
  subject      = {closo-Borane},
  language  = {en}
}