@article{LiuBudimanTianetal.2020, author = {Liu, Zhiqiang and Budiman, Yudha P. and Tian, Ya-Ming and Friedrich, Alexandra and Huang, Mingming and Westcott, Stephen A. and Radius, Udo and Marder, Todd B.}, title = {Copper-Catalyzed Oxidative Cross-Coupling of Electron-Deficient Polyfluorophenylboronate Esters with Terminal Alkynes}, series = {Chemistry - A European Journal}, volume = {26}, journal = {Chemistry - A European Journal}, number = {71}, doi = {10.1002/chem.202002888}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-224362}, pages = {17267 -- 17274}, year = {2020}, abstract = {We report herein a mild procedure for the copper-catalyzed oxidative cross-coupling of electron-deficient polyfluorophenylboronate esters with terminal alkynes. This method displays good functional group tolerance and broad substrate scope, generating cross-coupled alkynyl(fluoro)arene products in moderate to excellent yields. Thus, it represents a simple alternative to the conventional Sonogashira reaction.}, language = {en} } @article{BudimanWestcottRadiusetal.2021, author = {Budiman, Yudha P. and Westcott, Stephen A. and Radius, Udo and Marder, Todd B.}, title = {Fluorinated Aryl Boronates as Building Blocks in Organic Synthesis}, series = {Advanced Synthesis \& Catalysis}, volume = {363}, journal = {Advanced Synthesis \& Catalysis}, number = {9}, doi = {10.1002/adsc.202001291}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-225908}, pages = {2224 -- 2255}, year = {2021}, abstract = {Organoboron compounds are well known building blocks for many organic reactions. However, under basic conditions, polyfluorinated aryl boronic acid derivatives suffer from instability issues that are accelerated in compounds containing an ortho-fluorine group, which result in the formation of the corresponding protodeboronation products. Therefore, a considerable amount of research has focused on novel methodologies to synthesize these valuable compounds while avoiding the protodeboronation issue. This review summarizes the latest developments in the synthesis of fluorinated aryl boronic acid derivatives and their applications in cross-coupling reactions and other transformations. image}, language = {en} } @article{BischoffRieferWirthensohnetal.2020, author = {Bischoff, Lisa A. and Riefer, Jarno and Wirthensohn, Raphael and Bischof, Tobias and Bertermann, R{\"u}diger and Ignat'ev, Nikolai V. and Finze, Maik}, title = {Pentafluoroethylaluminates: A Combined Synthetic, Spectroscopic, and Structural Study}, series = {Chemistry - A European Journal}, volume = {26}, journal = {Chemistry - A European Journal}, number = {60}, doi = {10.1002/chem.202000667}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-214666}, pages = {13615 -- 13620}, year = {2020}, abstract = {Salts of the tetrakis(pentafluoroethyl)aluminate anion [Al(C\(_{2}\)F\(_{5}\))\(_{2}\)]\(^{-}\) were obtained from AlCl\(_{3}\) and LiC\(_{2}\)F\(_{5}\). They were isolated with different counter-cations and characterized by NMR and vibrational spectroscopy and mass spectrometry. Degradation of the [Al(C\(_{2}\)F\(_{5}\))\(_{4}\)]\(^{-}\) ion was found to proceed via 1,2-fluorine shifts and stepwise loss of CF(CF\(_{3}\)) under formation of [(C\(_{2}\)F\(_{5}\))\(_{4-n}\)AlF\(_{n}\)]- (n=1-4) as assessed by NMR spectroscopy and mass spectrometry and supported by results of DFT calculations. In addition, the [(C\(_{2}\)F\(_{5}\))AlF\(_{3}\)]\(^{-}\) ion was structurally characterized.}, language = {en} } @phdthesis{Budiman2020, author = {Budiman, Yudha Prawira}, title = {Applications of Fluorinated Aryl Boronates in Organic Synthesis}, doi = {10.25972/OPUS-21757}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-217579}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2020}, abstract = {Fluorinated compounds are an important motif, particularly in pharmaceuticals, as one-third of the top performing drugs have fluorine in their structures. Fluorinated biaryls also have numerous applications in areas such as material science, agriculture, crystal engineering, supramolecular chemistry, etc. Thus, the development of new synthetic routes to fluorinated chemical compounds is an important area of current research. One promising method is the borylation of suitable precursors to generate fluorinated aryl boronates as versatile building blocks for organic synthesis. Chapter 1 In this chapter, the latest developments in the synthesis, stability issues, and applications of fluorinated aryl boronates in organic synthesis are reviewed. The catalytic synthesis of fluorinated aryl boronates using different methods, such as C-H, C-F, and C-X (X = Cl, Br, I, OTf) borylations are discussed. Further studies covering instability issues of the fluorinated boronate derivatives, which are accelerated by ortho-fluorine, have been reported, and the applications of these substrates, therefore, need special treatment. Numerous groups have reported methods to employ highly fluorinated aryl boronates that anticipate the protodeboronation issue; thus, polyfluorinated aryl boronates, especially those containing ortho-fluorine substituents, can be converted into chloride, bromide, iodide, phenol, carboxylic acid, nitro, cyano, methyl esters, and aldehyde analogues. These substrates can be applied in many cross-coupling reactions, such as the Suzuki-Miyaura reaction with aryl halides, the Chan-Evans-Lam C-N reaction with aryl amines or nitrosoarenes, C-C(O) reactions with N-(aryl-carbonyloxy)phthalamides or thiol esters (Liebskind-Srogl cross-coupling), and oxidative coupling reactions with terminal alkynes. Furthermore, the difficult reductive elimination from the highly stable complex [PdL2(2,6-C6F2+nH3-n)2] was the next challenge to be targeted in the homocoupling of 2,6-di-fluoro aryl pinacol boronates, and it has been solved by conducting the reaction in arene solvents that reduce the energy barrier in this step as long as no coordinating solvent or ancillary ligand is employed. Chapter 2 In this chapter, phenanthroline-ligated copper complexes proved to be efficient catalysts for the Suzuki-Miyaura cross-coupling of highly fluorinated aryl boronate esters (ArF-Bpin) with aryl iodides or bromides. This newly developed method is an attractive alternative to the traditional methods as copper is an Earth-abundant metal, less toxic, and cheaper compared to the traditional methods which commonly required palladium catalysts, and silver oxide that is also often required in stoichiometric amounts. A combination of 10 mol\% copper iodide and 10 mol\% phenanthroline, with CsF as a base, in DMF, at 130 ˚C, for 18 hours is efficient to cross-couple fluorinated aryl pinacol boronates with aryl iodides to generate cross-coupled products in good to excellent yields. This method is also viable for polyfluorophenyl borate salts such as pentafluorophenyl-BF3K. Notably, employing aryl bromides instead of aryl iodides for the coupling with fluorinated aryl-Bpin compounds is also possible; however, increased amounts of CuI/phenanthroline catalyst is necessary, in a mixture of DMF and toluene (1:1). A diverse range of π···π stacking interactions is observed in the cross-coupling products partly perfluorinated biaryl crystals. They range from arene-perfluoroarene interactions (2-(perfluorophenyl)naphthalene and 2,3,4-trifluorobiphenyl) to arene-arene (9-perfluorophenyl)anthracene) and perfluoroarene-perfluoroarene (2,3,4,5,6-pentafluoro-2'methylbiphenyl) interactions. Chapter 3 In this chapter, the efficient Pd-catalyzed homocoupling reaction of aryl pinacol pinacol boronates (ArF-Bpin) that contain two ortho-fluorines is presented. The reaction must be conducted in a "noncoordinating" solvent such as toluene, benzene, or m-xylene and, notably, stronger coordinating solvents or ancillary ligands have to be avoided. Thus, the Pd center becomes more electron deficient and the reductive elimination becomes more favorable. The Pd-catalyzed homocoupling reaction of di-ortho-fluorinated aryl boronate derivatives is difficult in strongly coordinating solvents or in the presence of strong ancillary ligands, as the reaction stops at the [PdL2(2,6-C6F2+nH3-n)2] stage after the transmetalations without the reductive elimination taking place. It is known that the rate of reductive elimination of Ar-Ar from [ML2(Ar)(Ar)] complexes containing group-10 metals decreases in the order Arrich-Arpoor > Arrich-Arrich > Arpoor-Arpoor. Furthermore, reductive elimination of the most electron-poor diaryls, such as C6F5-C6F5, from [PdL2(C6F5)2] complexes is difficult and has been a challenge for 50 years, due to their high stability as the Pd-Caryl bond is strong. Thus, the Pd-catalyzed homocoupling of perfluoro phenyl boronates is found to be rather difficult.   Further investigation showed that stoichiometric reactions of C6F5Bpin, 2,4,6-trifluorophenyl-Bpin, or 2,6-difluorophenyl-Bpin with palladium acetate in MeCN stops at the double transmetalation step, as demonstrated by the isolation of cis-[Pd(MeCN)2(C6F5)2], cis-[Pd(MeCN)2(2,4,6-C6F3H2)2], and cis-[Pd(MeCN)2(2,6-C6F2H3)2] in quantitative yields. Thus, it can be concluded that the reductive elimination from diaryl-palladium complexes containing two ortho-fluorines in both aryl rings, is difficult even in a weakly coordinating solvent such as MeCN. Therefore, even less coordinating solvents are needed to make the Pd center more electron deficient. Reactions using "noncoordinating" arene solvents such as toluene, benzene, or m-xylene were conducted and found to be effective for the catalytic homocoupling of 2,6-C6F2+nH3-nBpin. The scope of the reactions was expanded. Using toluene as the solvent, the palladium-catalyzed homocoupling of ArF-Bpin derivatives containing one, two or no ortho-fluorines gave the coupled products in excellent yields without any difficulties. DFT calculations at the B3LYP-D3/def2-TZVP/6-311+g(2d,p)/IEFPCM // B3LYP-D3/SDD/6-31g**/IEFPCM level of theory predicted an exergonic process and lower barrier (< 21 kcal/mol) for the reductive elimination of Pd(C6F5)2 complexes bearing arene ligands, compared to stronger coordinating solvents (acetonitrile, THF, SMe2, and PMe3), which have high barriers ( > 33.7 kcal/mol). Reductive elimination from [Pd(ηn-Ar)(C6F5)2] complexes have low barriers due to: (i) ring slippage of the arene ligand as a hapticity change from η6 in the reactant to ηn (n ≤ 3) in the transition state and the product, which led to less σ-repulsion; and (ii) more favorable π-back-bonding from Pd(ArF)2 to the arene fragment in the transition state. Chapter 4 In this chapter, the efficient Pd-catalyzed C-Cl borylation of aryl chlorides containing two ortho-fluorines is presented. The reactions are conducted under base-free conditions to prevent the decomposition of the di-ortho-fluorinated aryl boronates, which are unstable in the presence of base. A combination of Pd(dba)2 (dba = dibenzylideneacetone) with SPhos (2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl) as a ligand is efficient to catalyze the C-Cl borylation of aryl chlorides containing two ortho-fluorine substituents without base, and the products were isolated in excellent yields. The substrate scope can be expanded to aryl chloride containing one or no ortho-fluorines and the borylated products were isolated in good to very good yield. This method provides a nice alternative to traditional methodologies using lithium or Grignard reagents.}, subject = {Homogene Katalyse}, language = {en} } @article{BudimanFriedrichRadiusetal.2019, author = {Budiman, Yudha P. and Friedrich, Alexandra and Radius, Udo and Marder, Todd B.}, title = {Copper-catalysed Suzuki-Miyaura cross-coupling of highly fluorinated aryl boronate esters with aryl iodides and bromides and fluoroarene-arene π-stacking interactions in the products}, series = {ChemCatChem}, volume = {11}, journal = {ChemCatChem}, number = {21}, doi = {10.1002/cctc.201901220}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204839}, pages = {5387-5396}, year = {2019}, abstract = {A combination of copper iodide and phenanthroline as the ligand is an efficient catalyst for Suzuki-Miyaura cross-coupling of highly fluorinated boronate esters (aryl-Bpin) with aryl iodides and bromides to generate fluorinated biaryls in good to excellent yields. This method represents a nice alternative to traditional cross-coupling methods which require palladium catalysts and stoichiometric amounts of silver oxide. We note that π⋅⋅⋅π stacking interactions dominate the molecular packing in the partly fluorinated biaryl crystals investigated herein. They are present either between the arene and perfluoroarene, or solely between arenes or perfluoroarenes, respectively.}, language = {en} } @article{WeiseBasseLuesebrinkKleinschnitzetal.2011, author = {Weise, Gesa and Basse-L{\"u}sebrink, Thomas C. and Kleinschnitz, Christoph and Kampf, Thomas and Jakob, Peter M. and Stoll, Guido}, title = {In Vivo Imaging of Stepwise Vessel Occlusion in Cerebral Photothrombosis of Mice by \(^{19}\)F MRI}, series = {PLoS One}, volume = {6}, journal = {PLoS One}, number = {12}, doi = {10.1371/journal.pone.0028143}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-137792}, pages = {e28143}, year = {2011}, abstract = {Background \(^{19}\)F magnetic resonance imaging (MRI) was recently introduced as a promising technique for in vivo cell tracking. In the present study we compared \(^{19}\)F MRI with iron-enhanced MRI in mice with photothrombosis (PT) at 7 Tesla. PT represents a model of focal cerebral ischemia exhibiting acute vessel occlusion and delayed neuroinflammation. Methods/Principal Findings Perfluorocarbons (PFC) or superparamagnetic iron oxide particles (SPIO) were injected intravenously at different time points after photothrombotic infarction. While administration of PFC directly after PT induction led to a strong \(^{19}\)F signal throughout the entire lesion, two hours delayed application resulted in a rim-like \(^{19}\)F signal at the outer edge of the lesion. These findings closely resembled the distribution of signal loss on T2-weighted MRI seen after SPIO injection reflecting intravascular accumulation of iron particles trapped in vessel thrombi as confirmed histologically. By sequential administration of two chemically shifted PFC compounds 0 and 2 hours after illumination the different spatial distribution of the \(^{19}\)F markers (infarct core/rim) could be visualized in the same animal. When PFC were applied at day 6 the fluorine marker was only detected after long acquisition times ex vivo. SPIO-enhanced MRI showed slight signal loss in vivo which was much more prominent ex vivo indicative for neuroinflammation at this late lesion stage. Conclusion Our study shows that vessel occlusion can be followed in vivo by \(^{19}\)F and SPIO-enhanced high-field MRI while in vivo imaging of neuroinflammation remains challenging. The timing of contrast agent application was the major determinant of the underlying processes depicted by both imaging techniques. Importantly, sequential application of different PFC compounds allowed depiction of ongoing vessel occlusion from the core to the margin of the ischemic lesions in a single MRI measurement.}, language = {en} }