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Eisch, John J.; Mackenzie, Kenneth D.; Windisch, Harald

doi:10.1002/(sici)1099-0682(199901)1999:1<153::aid-ejic153>3.3.co;2-s

Cited by 22 publications

(39 citation statements)

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“…Keywords: boranes · charge transfer · conjugation · electrochemistry · luminescence pyridazine binds more strongly than two equivalents of pyridine). [15,16] Given this background, a variety of symmetrically (R 1 = R 2 = H, [9] halogen, [13,[17][18][19][20] OR, [13] NR 2 , [19] alkyl, [21,22] aryl, [12,14,23] vinyl; [9] Figure 1) and unsymmetrically (R 1 = Mes, R 2 = H, Br, OR, vinyl; Mes = mesityl) [13] substituted DBAs have been synthesized and thoroughly characterized. However, a serious problem often encountered with compounds A lies in the sensitivity of their exocyclic B À R 1, 2 bonds toward air and moisture.…”

Section: Introductionmentioning

confidence: 99%

Boron‐Doped Tri(9,10‐anthrylene)s: Synthesis, Structural Characterization, and Optoelectronic Properties

Hoffend

Schödel

Bolte

et al. 2012

Chemistry A European J

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The reaction of 9,10-dibromo-9,10-dihydro-9,10-diboraanthracene (9,10-dibromo-DBA, 3) with two equivalents of 9-lithio-2,6- or 9-lithio-2,7-di-tert-butylanthracene gave the corresponding 9,10-dianthryl-DBAs featuring two (4) or four (5) inward-pointing tert-butyl groups. Compound 4 exists as two atropisomers, 4 and 4', due to hindered rotation about the exocyclic B-C bonds. X-ray crystallography of 5 suggests that the overall interactions between facing tert-butyl groups are attractive rather than repulsive. Even in solution, 4/4' and 5 are stable toward air and moisture for several hours. Treatment of 3 with 10-lithio-9-R-2,7-di-tert-butylanthracenes carrying phenyl (R=Ph), dimesitylboryl (R=Mes(2)B), or N,N-di(p-tolyl)amino (R=Tol(2)N) groups gave the corresponding 9,10-dianthryl-DBA derivatives 9-11 in moderate to good yields. In these molecules, all four solubilizing tert-butyl groups are outward pointing. The solid-state structures of 4, 5, 9, and 10 reveal twisted conformations about the exocyclic B-C bonds with dihedral angles of 70-90°. A significant electron-withdrawing character was proven for the Mes(2)B moiety, but no appreciable +M effect was evident for Tol(2)N. Compounds 5, 9, and 11 show two reversible DBA-centered reduction waves in the cyclic voltammogram. In the case of 10, a third reversible redox transition can be assigned to the Mes(2)B-anthryl substituents. The UV/Vis absorption spectrum of 5 is characterized by a very broad band at λ(max)=510 nm, attributable to a twisted intramolecular charge-transfer interaction from the anthryl donors to the DBA acceptor. The corresponding emission band shows pronounced positive solvatochromism (λ(em)=567 nm, C(6)H(12); 680 nm, CH(2)Cl(2)) in line with a highly polar excited state. The charge-transfer bands of 10 and 11, as well as the emission bands of 9 and 10, are redshifted relative to those of 5. The Tol(2)N derivative 11 is essentially nonfluorescent in solution, but emits bright wine-red light in the solid state.

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Section: Introductionmentioning

confidence: 99%

Boron‐Doped Tri(9,10‐anthrylene)s: Synthesis, Structural Characterization, and Optoelectronic Properties

Hoffend

Schödel

Bolte

et al. 2012

Chemistry A European J

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“…Keywords: boranes · borates · condensation · Grignard reaction · quantum chemistry change reaction. [43] 2) The electrochemical reduction of 1,2dihalobenzenes (1,2-C 6 H 4 X 2 ; X= Cl, Br, I) at a consumable Mg anode in the presence of pinacolborane (HBpin) provides a mixture of 1,2-C 6 H 4 A C H T U N G T R E N N U N G (Bpin) 2 (< 20 %), 1,2-C 6 H 4 -A C H T U N G T R E N N U N G (Bpin)(X), and C 6 H 5 A C H T U N G T R E N N U N G (Bpin). [44] 3) The cobalt-catalyzed cyclotrimerization of alkynylboranes gives mixtures of the 1,2,4and the 1,3,5-isomers; [45,46] one remarkable exception is the reaction of catB À C C À Bcat with [CpCo(CO) 2 ], which leads to hexaborylbenzene C 6 A C H T U N G T R E N N U N G (Bcat) 6 (H 2 cat = catechol).…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Coupling, and Condensation Reactions of 1,2‐Diborylated Benzenes: An Experimental and Quantum‐Chemical Study

Seven

Zhu

et al. 2012

Chemistry A European J

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1,2-Bis(pinacolboryl)benzene (1,2-C(6)H(4) (Bpin)(2), 2) was synthesized in preparatively useful yields from 1,2-C(6)H(4)Br(2), iPrO-Bpin, and Mg turnings in the presence of 1,2-C(2)H(4)Br(2) as an entrainer. Compound 2 is a versatile starting material for the synthesis of (un)symmetrically substituted benzenes (i.e., 1,2-C(6)H(4)(Ar(1))(Ar(2))) through sequential Suzuki-Miyaura coupling reactions. Alternatively, it can be transformed into bis-borate Li(2)[1,2-C(6)H(4)(BH(3))(2)] (3) through reduction with Li[AlH(4)]. In the crystal lattice, the diethyl ether solvate 3·OEt(2) establishes a columnar structure that is reinforced by an intricate network of B-(μ-H)-Li interactions. Hydride-abstraction from compound 3 with Me(3)SiCl leads to the transient ditopic borane 1,2-C(6)H(4)(BH(2))(2), which can either be used in situ for subsequent hydroboration reactions or trapped as its stable NMe(2)Et diadduct (6). In SMe(2) solution, the putative diadduct 1,2-C(6)H(4)(BH(2)·SMe(2))(2) is not long-term stable but rather undergoes a condensation reaction to give 9,10-dihydro-9,10-diboraanthracene, HB(μ-C(6)H(4))(2)BH, and BH(3). 9,10-Dihydro-9,10-diboraanthracene was isolated from the reaction mixture as its SMe(2) monoadduct (7), which dimerizes in the solid state through two B-H-B bridges ((7)(2), elucidated by X-ray crystallography). In contrast, hydride-abstraction from compound 3 in THF or CH(2)Cl(2) provides the unique exo-adduct H(2)B(μ-H)(2)B(μ-C(6)H(4))(2)B(μ-H)(2)BH(2) (8, elucidated by X-ray crystallography). Quantum-chemical calculations on various conceivable isomers of [1,2-C(6)H(4)(BH(2))(2)](2) revealed that compound 8 was the most stable of these species. Moreover, the calculations confirmed the experimental findings that the NMe(2)Et diadduct of 1,2-C(6)H(4)(BH(2))(2) is significantly more stable than the corresponding SMe(2) complex and that the latter complex is not able to compete successfully with borane-dimerization and -condensation. The reaction cascade in SMe(2), which proceeds from 1,2-C(6)H(4)(BH(2))(2) to the observed adducts of HB(μ-C(6)H(4))(2)BH, has been elucidated in detail and the important role of B-C-B-bridged intermediates has been firmly established.

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“…Clearly, several boron-containing products are formed in a solventdependent manner. The spectrum of the reaction mixture formed in toluene (Figure 1 a) shows peaks at d = 85.7, 77.4, and 71.9 ppm, assigned as BEt 3 , [14] BEt 2 Ph, [15] and BEtPh 2 , respectively. Triphenylboron has been shown to act as a useful aryl source in B-Zn transmetallation processes, [ 7a, 16] thus the observed arylboranes may well act as "reservoirs" for the aryl nucleophile.…”

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confidence: 99%

Exploiting Boron–Zinc Transmetallation for the Arylation of Benzyl Halides: What are the Reactive Species?

Bedford¹,

Gower²,

Haddow³

et al. 2012

Angew Chem Int Ed

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One step Beyond: The transmetallation reactions of ArB(OH)2 and Ar3B3O3 with Et2Zn are far more complicated than previously supposed, with solvent‐dependent equilibria between ArB(OY)2 at one side and [RZn(solv)3][BR4] at the other (see picture). While the role of the highly reactive organozinc cation has not been implicated before, its importance for the activation of an otherwise sluggish class of electrophiles is shown.

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Cited by 22 publications

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Boron‐Doped Tri(9,10‐anthrylene)s: Synthesis, Structural Characterization, and Optoelectronic Properties

Boron‐Doped Tri(9,10‐anthrylene)s: Synthesis, Structural Characterization, and Optoelectronic Properties

Synthesis, Coupling, and Condensation Reactions of 1,2‐Diborylated Benzenes: An Experimental and Quantum‐Chemical Study

Exploiting Boron–Zinc Transmetallation for the Arylation of Benzyl Halides: What are the Reactive Species?

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