259-79-0Relevant articles and documents
Structure-Property Relationships in Unsymmetric Bis(antiaromatics): Who Wins the Battle between Pentalene and Benzocyclobutadiene? ?
El Bakouri, Ouissam,Holczbauer, Tamás,Janáky, Csaba,London, Gábor,Mayer, Péter J.,Ottosson, Henrik,Samu, Gergely F.
, p. 5158 - 5172 (2020)
According to the currently accepted structure-property relationships, aceno-pentalenes with an angular shape (fused to the 1,2-bond of the acene) exhibit higher antiaromaticity than those with a linear shape (fused to the 2,3-bond of the acene). To explore and expand the current view, we designed and synthesized molecules where two isomeric, yet, different, 8πantiaromatic subunits, a benzocyclobutadiene (BCB) and a pentalene, are combined into, respectively, an angular and a linear topology via an unsaturated six-membered ring. The antiaromatic character of the molecules is supported experimentally by 1H NMR, UV-vis, and cyclic voltammetry measurements and X-ray crystallography. The experimental results are further confirmed by theoretical studies including the calculation of several aromaticity indices (NICS, ACID, HOMA, FLU, MCI). In the case of the angular molecule, double bond-localization within the connecting six-membered ring resulted in reduced antiaromaticity of both the BCB and pentalene subunits, while the linear structure provided a competitive situation for the two unequal [4n]πsubunits. We found that in the latter case the BCB unit alleviated its unfavorable antiaromaticity more efficiently, leaving the pentalene with strong antiaromaticity. Thus, a reversed structure-antiaromaticity relationship when compared to aceno-pentalenes was achieved.
Coumarin (5,6-Benzo-2-pyrone) Trapping of an HDDA-Benzyne
Chinta, Bhavani Shankar,Lee, Daniel,Hoye, Thomas R.
, p. 2189 - 2193 (2021)
Although the parent 2-pyrone is known to react with simple o-benzynes to produce naphthalene derivatives, there appear to be no examples of the successful reaction of coumarin, a benzo-annulated 2-pyrone analogue, with an aryne. We report such a process here using benzynes generated by the hexadehydro-Diels-Alder reaction to produce phenanthrene derivatives (i.e., benzo-annulated naphthalenes). Density functional theory computations were used to help understand the difference in reactivity between 2-pyrone and the slower trapping agent, coumarin. Finally, the reaction of o-benzyne itself [from o-(trimethylsilyl)phenyl triflate and CsF] with coumarin was shown to be viable, although slow.
A convenient synthesis of biphenylene
Schaub, Thomas,Radius, Udo
, p. 8195 - 8197 (2005)
An efficient one-pot reaction for the synthesis of biphenylene 1 starting from biphenyl is reported. The final product was prepared from commercially available, cheap materials in moderate yet very competitive yield. Biphenyl was ortho-lithiated to 2,2′-dilithiobiphenyl 2, which was then coupled to biphenylene.
Benzodisilacyclobutadienes: 8π-Electron Systems with an Antiaromatic Silicon Ring
Ishida, Shintaro,Misawa, Yoshifumi,Sugawara, Shohei,Iwamoto, Takeaki
, p. 13829 - 13832 (2017)
Benzodisilacyclobutadienes 2 a–c were isolated as blue to green crystalline solids from the reaction of stable disilyne 1 and 1,2-dibromobenzenes in the presence of potassium graphite. In the solid state, substantial bond alternation was observed within the benzene rings of 2 a–c. In hexane, 2 a–c showed remarkable bathochromic shifts of the π→π* (HOMO→LUMO) absorption bands at 625–670 nm. NMR spectra and theoretical calculations indicated that the diamagnetic ring currents of the benzene rings of 2 a–c are considerably reduced by contributions from the antiaromatic 1,2-disilacyclobutadienes. In their entirety, the obtained results indicate that 2 a–c represent 8π-electron systems that contain an antiaromatic 1,2-disilacyclobutadiene.
Formation of biphenylene by elimination of C2 from 9,10-didehydrophenanthrene at 1100°C
Brown, Roger F.C.,Coulston, Karen J.,Eastwood, Frank W.
, p. 6819 - 6820 (1996)
Flash vacuum pyrolysis of phenanthrene-9,10-dicarboxylic anhydride 5 and of 2,2-dimethyl-5-(9'-fluorenylidene)-1,3-dioxan-4,6-dione 8 at 1100°C/0.03-0.04 mm Hg gave pyrolysates which were analysed by 1H NMR spectroscopy and shown to contain phenanthrene 9 as a major constituent and biphenylene 2 as a minor one.
An ESR study of the mercuration of the biphenylene radical cation. Evidence for a homolytic mechanism of mercuration
Courtneidge, John L.,Davies, Alwyn G.,McGuchan, Deborah C.,Yazdi, Safieh N.
, p. 63 - 72 (1988)
When a solution of biphenylene in trifluoroacetic acid containing mercury(II) trifluoroacetate is photolysed with ultraviolet light, the ESR spectra show the progressive mercuration of the biphenylene radical cation in the β-position. β-Proton hyperfine coupling β) 76-77 G> appear until tetra-β-mercuration is complete.It is concluded that, apart from the usual electrophilic mechanism, an alternative mechanism for mercuration exists, and that this probably involves collapse of the aromatic radical cation, ArH+., with its counterion, HgX2-.: ArH + HgX2 -> ArH+. + HgX2-. -> HArHgX2 -> ArHgX + HX.
Could London Dispersion Force Control Regioselective (2 + 2) Cyclodimerizations of Benzynes? YES: Application to the Synthesis of Helical Biphenylenes
Akai, Shuji,Aoyama, Hiroshi,Fukumoto, Yutaka,Heguri, Akito,Ikawa, Takashi,Masuda, Yuto,Murakami, Tomonari,Shigeta, Yasuteru,Takagi, Akira,Tokiwa, Hiroaki,Yahata, Kenzo,Yamamoto, Yuta
, p. 10853 - 10859 (2021/07/26)
In recent years, London dispersion interactions, which are the attractive component of the van der Waals potential, have been found to play an important role in controlling the regio- and/or stereoselectivity of various reactions. Particularly, the dispersion interactions between substrates and catalysts (or ligands) are dominant in various selective catalyzes. In contrast, repulsive steric interactions, rather than the attractive dispersion interactions, between bulky substituents are predominant in most of the noncatalytic reactions. Herein, we demonstrate the first example of London dispersion-controlled noncatalytic (2 + 2) cyclodimerization of substituted benzynes to selectively afford proximal biphenylenes in high yields and regioselectivities, depending on the extent of dispersion interactions in the substituents. This method can be applied for the synthesis of novel helical biphenylenes, which would be fascinating for chemists as these compounds are potential skeletons for ligands, catalysts, and medicines.
Experimental and theoretical studies on gold(iii) carbonyl complexes: reductive C,H- And C,C bond formation
Ahrens, Alexander,Dreuw, Andreas,Hashmi, A. S. K.,Hoffmann, Marvin,Karger, Leonhard F. P.,Lustosa, Danilo M.,Rudolph, Matthias
supporting information, p. 8752 - 8760 (2021/07/02)
The reactivity of cationic (C^C)gold(iii) carbonyl complexes was investigated. While thein situ-formed IPrAu(bph)CO+complex (bph = biphenyl-2,2′-diyl) does not undergo a migratory insertion of CO into the neighboring gold-carbon bond, nucleophiles can attack the coordinated CO moiety intermolecularly. Water as a nucleophile initiates a CO2extrusion combined with a reductive C,H bond formation. The rapid formation of a gold(i) species from an intermediary gold(iii) carbonyl has not been observed before and shows a significant difference in reactivity between (C^C) and (C^N^C)gold(iii) carbonyls. The latter have been reported to form stable gold(iii) hydridesviathe WGS reaction. In the case of methanol acting as a nucleophile attacking the gold(iii) carbonyl, no extrusion of CO2is observed. Instead an intermediary gold(iii) carboxyl complex forms an aryl carboxylateviareductive C-C bond elimination. Experimental and theoretical studies on the mechanism explain the observed selectivities and give new insights into the reactivity of elusive gold(iii) carbonyls.
Metal-Free Selective Borylation of Arenes by a Diazadiborinine via C-H/C-F Bond Activation and Dearomatization
Su, Yuanting,Huan Do, Dinh Cao,Li, Yongxin,Kinjo, Rei
supporting information, p. 13729 - 13733 (2019/09/30)
A newly developed annulated 5-chlorinated 1,3,2,5-diazadiborinine derivative (4) selectively activates a C-H bond of benzene (C6H6) and 1,3-di(trifluoromethyl)benzene, as well as a C-F bond in partially fluorinated arenes, to furnish borylation products under catalyst-, metal-, and irradiation-free conditions. Moreover, 4 readily undergoes a reversible dearomative coupling reaction with polycyclic aromatic hydrocarbons to afford diboration products. The latter represents the first reversible intermolecular dearomative diboration of arenes.
How πextension or Structural Bending Alters the Properties of Boron-Doped Phenylene-Containing Oligoacenes
Kirschner, Sven,Uecker, Ise,Bolte, Michael,Lerner, Hans-Wolfram,Wagner, Matthias
supporting information, p. 2818 - 2823 (2019/08/12)
Linear annulation of two 2,3-biphenylenediyl moieties to a 1,4-dibora-2,5-cyclohexadiene core via its carbon atoms leads to the boron-doped phenylene-containing oligoacene (B-POA) DBI. The optoelectronic properties of DBI are unlike those of related boron-doped polycyclic aromatic hydrocarbons (B-PAHs), such as 6,13-dihydro-6,13-diborapentacene (DBP). Herein we disclose two new B-POAs, which provide insight into fundamental structure-property relationships. The first is a π-extended DBI congener (e-DBI), in which two 2,3-benzo[b]biphenylenediyl moieties are linearly annulated to the central B2C4 ring and behaves partly similar to DBI: it is a strong electron acceptor and has a deep red color. In contrast to the nonluminescent DBI, it shows red fluorescence (quantum yield: 12%), which changes to blue-green upon addition of excess F--ions. In the presence of 0.4 equiv of F-, nearly white emission is observed (CIE1931: (0.3320|0.4056)). If biphenylenediyl moieties are angularly attached to the B2C4 ring via their 1,2-positions, the resulting mixture of "v"- and "z"-shaped B-POA isomers (v/z-DBI) behaves distinctly different from linear DBI: the electrode potentials required for the reversible two-electron reductions of v/z-DBI are significantly more cathodic, and v/z-DBI is an orange rather than red solid and emits green light (quantum yields 65%) upon irradiation.
