@article{LindlLamprechtArrowsmithetal.2023, author = {Lindl, Felix and Lamprecht, Anna and Arrowsmith, Merle and Khitro, Eugen and Rempel, Anna and Dietz, Maximilian and Wellnitz, Tim and B{\´e}langer-Chabot, Guillaume and Stoy, Andreas and Paprocki, Valerie and Prieschl, Dominik and Lenczyk, Carsten and Ramler, Jacqueline and Lichtenberg, Crispin and Braunschweig, Holger}, title = {Aromatic 1,2-Azaborinin-1-yls as Electron-Withdrawing Anionic Nitrogen Ligands for Main Group Elements}, series = {Chemistry - A European Journal}, volume = {29}, journal = {Chemistry - A European Journal}, number = {11}, doi = {10.1002/chem.202203345}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-312222}, year = {2023}, abstract = {The 2-aryl-3,4,5,6-tetraphenyl-1,2-azaborinines 1-EMe\(_{3}\) and 2-EMe\(_{3}\) (E=Si, Sn; aryl=Ph (1), Mes (=2,4,6-trimethylphenyl, 2)) were synthesized by ring-expansion of borole precursors with N\(_{3}\)EMe\(_{3}\)-derived nitrenes. Desilylative hydrolysis of 1- and 2-SiMe\(_{3}\) yielded the corresponding N-protonated azaborinines, which were deprotonated with nBuLi or MN(SiMe\(_{3}\))\(_{2}\) (M=Na, K) to the corresponding group 1 salts, 1-M and 2-M. While the lithium salts crystallized as monomeric Lewis base adducts, the potassium salts formed coordination polymers or oligomers via intramolecular K⋅⋅⋅aryl π interactions. The reaction of 1-M or 2-M with CO\(_{2}\) yielded N-carboxylate salts, which were derivatized by salt metathesis to methyl and silyl esters. Salt metathesis of 1-M or 2-M with methyl triflate, [Cp*BeCl] (Cp*=C\(_{5}\)Me\(_{5}\)), BBr\(_{2}\)Ar (Ar=Ph, Mes, 2-thienyl), ECl\(_{3}\) (E=B, Al, Ga) and PX\(_{3}\) (X=Cl, Br) afforded the respective group 2, 13 and 15 1,2-azaborinin-2-yl complexes. Salt metathesis of 1-K with BBr\(_{3}\) resulted not only in N-borylation but also Ph-Br exchange between the endocyclic and exocyclic boron atoms. Solution \(^{11}\)B NMR data suggest that the 1,2-azaborinin-2-yl ligand is similarly electron-withdrawing to a bromide. In the solid state the endocyclic bond length alternation and the twisting of the C\(_{4}\)BN ring increase with the sterics of the substituents at the boron and nitrogen atoms, respectively. Regression analyses revealed that the downfield shift of the endocyclic \(^{11}\)B NMR resonances is linearly correlated to both the degree of twisting of the C\(_{4}\)BN ring and the tilt angle of the N-substituent. Calculations indicate that the 1,2-azaborinin-1-yl ligand has no sizeable π-donor ability and that the aromaticity of the ring can be subtly tuned by the electronics of the N-substituent.}, language = {en} } @article{LindlGuoKrummenacheretal.2021, author = {Lindl, Felix and Guo, Xueying and Krummenacher, Ivo and Rauch, Florian and Rempel, Anna and Paprocki, Valerie and Dellermann, Theresa and Stennett, Tom E. and Lamprecht, Anna and Br{\"u}ckner, Tobias and Radacki, Krzysztof and B{\´e}langer-Chabot, Guillaume and Marder, Todd B. and Lin, Zhenyang and Braunschweig, Holger}, title = {Rethinking Borole Cycloaddition Reactivity}, series = {Chemistry—A European Journal}, volume = {27}, journal = {Chemistry—A European Journal}, number = {43}, doi = {10.1002/chem.202101290}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256888}, pages = {11226-11233}, year = {2021}, abstract = {Boroles are attracting broad interest for their myriad and diverse applications, including in synthesis, small molecule activation and functional materials. Their properties and reactivity are closely linked to the cyclic conjugated diene system, which has been shown to participate in cycloaddition reactions, such as the Diels-Alder reaction with alkynes. The reaction steps leading to boranorbornadienes, borepins and tricyclic boracyclohexenes from the thermal reaction of boroles with alkynes are seemingly well understood as judged from the literature. Herein, we question the long-established mechanistic picture of pericyclic rearrangements by demonstrating that seven-membered borepins (i. e., heptaphenylborepin and two derivatives substituted with a thienyl and chloride substituent on boron) exist in a dynamic equilibrium with the corresponding bicyclic boranorbornadienes, the direct Diels-Alder products, but are not isolable products from the reactions. Heating gradually converts the isomeric mixtures into fluorescent tricyclic boracyclohexenes, the most stable isomers in the series. Results from mechanistic DFT calculations reveal that the tricyclic compounds derive from the boranorbornadienes and not the borepins, which were previously believed to be intermediates in purely pericyclic processes.}, language = {en} } @article{HagspielArrowsmithFantuzzietal.2021, author = {Hagspiel, Stephan and Arrowsmith, Merle and Fantuzzi, Felipe and Vargas, Alfredo and Rempel, Anna and Hermann, Alexander and Br{\"u}ckner, Tobias and Braunschweig, Holger}, title = {Highly colored boron-doped thiazolothiazoles from the reductive dimerization of boron isothiocyanates}, series = {Angewandte Chemie International Edition}, volume = {60}, journal = {Angewandte Chemie International Edition}, number = {12}, doi = {10.1002/anie.202015508}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256432}, pages = {6446-6450}, year = {2021}, abstract = {Reduction of (CAAC)BBr\(_2\)(NCS) (CAAC=cyclic alkyl(amino)carbene) in the presence of a Lewis base L yields tricoordinate (CAAC)LB(NCS) borylenes which undergo reversible E/Z-isomerization. The same reduction in the absence of L yields deep blue, bis(CAAC)-stabilized, boron-doped, aromatic thiazolothiazoles resulting from the dimerization of dicoordinate (CAAC)B(NCS) borylene intermediates.}, language = {en} } @article{BruecknerHessStennettetal.2021, author = {Br{\"u}ckner, Tobias and Heß, Merlin and Stennett, Tom E. and Rempel, Anna and Braunschweig, Holger}, title = {Synthesis of Boron Analogues of Enamines via Hydroamination of a Boron-Boron Triple Bond}, series = {Angewandte Chemie, International Edition}, volume = {60}, journal = {Angewandte Chemie, International Edition}, number = {2}, doi = {10.1002/anie.202012101}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-240669}, pages = {736-741}, year = {2021}, abstract = {An N-heterocyclic-carbene-stabilized diboryne undergoes rapid, high-yielding and catalyst-free hydroamina- tion reactions with primary amines, yielding 1-amino-2-hydro- diborenes, which can be considered boron analogues of enamines. The electronics of the organic substituent at nitrogen influence the structure and further reactivity of the diborene product. With electron-rich anilines, a second hydroamination can occur at the diborene to generate 1,1-diamino-2,2-dihy- drodiboranes. With isopropylamine, the electronic influence of the alkyl substituent upon the diborene leads to an unprece- dented boron-mediated intramolecular N-dearylation reaction of an N-heterocyclic carbene unit.}, language = {en} } @unpublished{SchmidtFantuzziArrowsmithetal.2020, author = {Schmidt, Uwe and Fantuzzi, Felipe and Arrowsmith, Merle and Hermann, Alexander and Prieschl, Dominic and Rempel, Anna and Engels, Bernd and Braunschweig, Holger}, title = {Tuneable reduction of cymantrenylboranes to diborenes or borylene-derived boratafulvenes}, series = {Chemical Communications}, journal = {Chemical Communications}, doi = {10.1039/D0CC06398C}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-222149}, year = {2020}, abstract = {Whereas the reduction of N-heterocyclic carbene (NHC)-stabilised cymantrenyldibromoboranes, (NHC)BBr\(_2\)Cym, in benzene results in formation of the corresponding diborenes (NHC)\(_2\)B\(_2\)Cym\(_2\), a change of solvent to THF yields a borylene of the form (NHC)\(_2\)BCym, stabilised through its boratafulvene resonance form.}, language = {en} } @article{LiuLegareSeufertetal.2020, author = {Liu, Siyuan and L{\´e}gar{\´e}, Marc-Andr{\´e} and Seufert, Jens and Prieschl, Dominic and Rempel, Anna and Englert, Lukas and Dellermann, Theresa and Paprocki, Valerie and Stoy, Andreas and Braunschweig, Holger}, title = {2,2′-Bipyridyl as a Redox-Active Borylene Abstraction Agent}, series = {Inorganic Chemistry}, volume = {59}, journal = {Inorganic Chemistry}, number = {15}, doi = {10.1021/acs.inorgchem.0c01383}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-215595}, pages = {10866-10873}, year = {2020}, abstract = {2,2′-Bipyridyl is shown to spontaneously abstract a borylene fragment (R-B:) from various hypovalent boron compounds. This process is a redox reaction in which the bipyridine is reduced and becomes a dianionic substituent bound to boron through its two nitrogen atoms. Various transition metal-borylene complexes and diboranes, as a well as a diborene, take part in this reaction. In the latter case, our results show an intriguing example of the homolytic cleavage of a B═B double bond.}, language = {en} } @article{BraunschweigConstantinidisDellermannetal.2016, author = {Braunschweig, Holger and Constantinidis, Philipp and Dellermann, Theresa and Ewing, William and Fischer, Ingo and Hess, Merlin and Knight, Fergus and Rempel, Anna and Schneider, Christoph and Ullrich, Stefan and Vargas, Alfredo and Woolins, Derek}, title = {Highly Strained Heterocycles Constructed from Boron-Boron Multiple Bonds and Heavy Chalcogens}, series = {Angewandte Chemie, International Edition}, volume = {55}, journal = {Angewandte Chemie, International Edition}, number = {18}, doi = {10.1002/anie.201601691}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-138237}, pages = {5606 -- 5609}, year = {2016}, abstract = {The reactions of a diborene with elemental selenium or tellurium are shown to afford a diboraselenirane or diboratellurirane, respectively. These reactions are reminiscent of the sequestration of subvalent oxygen and nitrogen in the formation of oxiranes and aziridines; however, such reactivity is not known between alkenes and the heavy chalcogens. Although carbon is too electronegative to affect the reduction of elements with lower relative electronegativity, the highly reducing nature of the B B double bond enables reactions with Se0 and Te0. The capacity of multiple bonds between boron atoms to donate electron density is highlighted in reactions where diborynes behave as nucleophiles, attacking one of the two Te atoms of diaryltellurides, forming salts consisting of diboratellurenium cations and aryltelluride anions.}, subject = {Bor}, language = {en} }