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.
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.
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.
Brown et al.
, p. 407 (1966)
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.
