@article{ZhangFriedrichMarder2022, author = {Zhang, Xiaolei and Friedrich, Alexandra and Marder, Todd B.}, title = {Copper-Catalyzed Borylation of Acyl Chlorides with an Alkoxy Diboron Reagent: A Facile Route to Acylboron Compounds}, series = {Chemistry—A European Journal}, volume = {28}, journal = {Chemistry—A European Journal}, number = {42}, doi = {10.1002/chem.202201329}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-318318}, year = {2022}, abstract = {Herein, the copper-catalyzed borylation of readily available acyl chlorides with bis(pinacolato)diboron, (B\(_{2}\)pin\(_{2}\)) or bis(neopentane glycolato)diboron (B\(_{2}\)neop\(_{2}\)) is reported, which provides stable potassium acyltrifluoroborates (KATs) in good yields from the acylboronate esters. A variety of functional groups are tolerated under the mild reaction conditions (room temperature) and substrates containing different carbon-skeletons, such as aryl, heteroaryl and primary, secondary, tertiary alkyl are applicable. Acyl N-methyliminodiacetic acid (MIDA) boronates can also been accessed by modification of the workup procedures. This process is scalable and also amenable to the late-stage conversion of carboxylic acid-containing drugs into their acylboron analogues, which have been challenging to prepare previously. A catalytic mechanism is proposed based on in situ monitoring of the reaction between p-toluoyl chloride and an NHC-copper(I) boryl complex as well as the isolation of an unusual lithium acylBpinOBpin compound as a key intermediate.}, 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{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} } @phdthesis{Huang2022, author = {Huang, Mingming}, title = {C-S Bond Borylation and Diborylation of Alkyl Halides, Tosylates, and Alcohols}, doi = {10.25972/OPUS-25718}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257186}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2022}, abstract = {Alkylboronates play an important role in synthetic chemistry, materials science and drug discovery. They are easy to handle due to their good air and moisture stability, and can be readily employed to form carbon-carbon and carbon-heteroatom bonds and can be converted to various functional groups under mild reaction conditions. Compared with conventional groups, such as aryl (pseudo)halides or alcohols, organosulfur compounds represent an alternative and complimentary substitute in coupling reactions. The construction of C-B bond from C-SO bond of aryl sulfoxide is presented in Chapter 2. The selective cleavage of either alkyl(C)-sulfonyl or aryl(C)-sulfonyl bonds of an aryl alkyl sulfone via Cu-free or Cu-mediated processes generates the corresponding boronate esters, which are presented in Chapter 3 and Chapter 4. 1,2-Bis(boronate esters) are emerging as important synthetic intermediates for preparing 1,2-difunctional compounds. In addition, the boryl moieties in different environments in a 1,2-bis(boronate ester) can be differentiated and converted selectively, allowing the synthesis of a wide variety of complex molecules. A direct and selective diboration of C-X and C-O bonds for the preparation of 1,2-bis(boronate esters) is presented in Chapter 5.}, language = {en} } @article{BudimanLorenzenLiuetal.2021, author = {Budiman, Yudha P. and Lorenzen, Sabine and Liu, Zhiqiang and Radius, Udo and Marder, Todd B.}, title = {Base-Free Pd-Catalyzed C-Cl Borylation of Fluorinated Aryl Chlorides}, series = {Chemistry - A European Journal}, volume = {27}, journal = {Chemistry - A European Journal}, number = {11}, doi = {10.1002/chem.202004648}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-225687}, pages = {3869 -- 3874}, year = {2021}, abstract = {Catalytic C-X borylation of aryl halides containing two ortho-fluorines has been found to be challenging, as most previous methods require stoichiometric amounts of base and the polyfluorinated aryl boronates suffer from protodeboronation, which is accelerated by ortho-fluorine substituents. Herein, we report that 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. This method, conducted under base-free conditions, is compatible with the resulting di-ortho-fluorinated aryl boronate products which are sensitive to base.}, language = {en} } @article{MerzDietrichNitschetal.2020, author = {Merz, Julia and Dietrich, Lena and Nitsch, J{\"o}rn and Krummenacher, Ivo and Braunschweig, Holger and Moos, Michael and Mims, David and Lambert, Christoph and Marder, Todd B.}, title = {Synthesis, Photophysical and Electronic Properties of Mono-, Di-, and Tri-Amino-Substituted Ortho-Perylenes, and Comparison to the Tetra-Substituted Derivative}, series = {Chemistry - A European Journal}, volume = {26}, journal = {Chemistry - A European Journal}, number = {52}, doi = {10.1002/chem.202001475}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-217835}, pages = {12050 -- 12059}, year = {2020}, abstract = {We synthesized a series of new mono-, di-, tri- and tetra-substituted perylene derivatives with strong bis(para-methoxyphenyl)amine (DPA) donors at the uncommon 2,5,8,11-positions. The properties of our new donor-substituted perylenes were studied in detail to establish a structure-property relationship. Interesting trends and unusual properties are observed for this series of new perylene derivatives, such as a decreasing charge transfer (CT) character with increasing number of DPA moieties and individual reversible oxidations for each DPA moiety. Thus, (DPA)-Per possesses one reversible oxidation while (DPA)\(_{4}\)-Per has four. The mono- and di-substituted derivatives display unusually large Stokes shifts not previously reported for perylenes. Furthermore, transient absorption measurements of the new derivatives reveal an excited state with lifetimes of several hundred microseconds, which sensitizes singlet oxygen with quantum yields of up to 0.83.}, language = {en} } @article{LiuMingLuoetal.2020, author = {Liu, Xiaocui and Ming, Wenbo and Luo, Xiaoling and Friedrich, Alexandra and Maier, Jan and Radius, Udo and Santos, Webster L. and Marder, Todd B.}, title = {Regio- and Stereoselective Synthesis of 1,1-Diborylalkenes via Br{\o}nsted Base-Catalyzed Mixed Diboration of Alkynyl Esters and Amides with BpinBdan}, series = {European Journal of Organic Chemistry}, volume = {2020}, journal = {European Journal of Organic Chemistry}, number = {13}, doi = {10.1002/ejoc.202000128}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-214728}, pages = {1941 -- 1946}, year = {2020}, abstract = {The NaOtBu-catalyzed mixed 1,1-diboration of terminal alkynes using the unsymmetrical diboron reagent BpinBdan (pin = pinacolato; dan = 1,8-diaminonaphthalene) proceeds in a regio- and stereoselective fashion affording moderate to high yields of 1,1-diborylalkenes bearing orthogonal boron protecting groups. It is applicable to gram-scale synthesis without loss of yield or selectivity. The mixed 1,1-diborylalkene products can be utilized in Suzuki-Miyaura cross-coupling reactions which take place selectivly at the C-B site. DFT calculations suggest the NaOtBu-catalyzed mixed 1,1-diboration of alkynes occurs through deprotonation of the terminal alkyne, stepwise addition of BpinBdan to the terminal carbon followed by protonation with tBuOH. Experimentally observed selective formation of (Z)-diborylalkenes is supported by our theoretical studies.}, language = {en} } @phdthesis{Ming2021, author = {Ming, Wenbo}, title = {Synthesis of α‑Aminoboronates and PBP Pincer Palladium Boryl Complexes}, doi = {10.25972/OPUS-19832}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-198323}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2021}, abstract = {The first Borono-Strecker reaction has been developed to synthesize α-aminoboronates via a multicomponent reaction of readily available carbonyl compounds (aldehydes and ketones), amines and B2pin2. The preparation of α-amino cyclic boronates can be achieved via multicomponent coupling of salicylaldehydes, amines, and B2(OH)4. In addition, the diazaborole-based PBP pincer palladium chloride and the diazaborole-based PBP pincer palladium trifluoromethanesulfonate complexes were synthesized and fully characterized for the first time, and used as catalysts for Suzuki-Miyaura cross-coupling reactions.}, 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{LiuMingFriedrichetal.2020, author = {Liu, Xiaocui and Ming, Wenbo and Friedrich, Alexandra and Kerner, Florian and Marder, Todd B.}, title = {Copper-Catalyzed Triboration of Terminal Alkynes Using B\(_2\)pin\(_2\): Efficient Synthesis of 1,1,2-Triborylalkenes}, series = {Angewandte Chemie International Edition}, volume = {59}, journal = {Angewandte Chemie International Edition}, number = {1}, doi = {10.1002/anie.201908466}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-206694}, pages = {304-309}, year = {2020}, abstract = {We report herein the catalytic triboration of terminal alkynes with B\(_2\)pin\(_2\) (bis(pinacolato)diboron) using readily available Cu(OAc)\(_2\) and P\(^n\)Bu\(_3\). Various 1,1,2-triborylalkenes, a class of compounds that have been demonstrated to be potential matrix metalloproteinase (MMP-2) inhibitors, were obtained directly in moderate to good yields. The process features mild reaction conditions, a broad substrate scope, and good functional group tolerance. This copper-catalyzed reaction can be conducted on a gram scale to produce the corresponding 1,1,2-triborylalkenes in modest yields. The utility of these products was demonstrated by further transformations of the C-B bonds to prepare gem -dihaloborylalkenes (F, Cl, Br), monohaloborylalkenes (Cl, Br), and trans -diaryldiborylalkenes, which serve as important synthons and have previously been challenging to prepare.}, language = {en} }