203-33-8Relevant articles and documents
Probing mechanisms of aryl-aryl bond cleavages under flash vacuum pyrolysis conditions
Jackson, Edward A.,Xue, Xiang,Cho, Hee Yeon,Scott, Lawrence T.
, p. 1279 - 1287 (2014/11/08)
Several biaryls have been subjected to flash vacuum pyrolysis (FVP) at 1100°C and 0.8-0.9hPa. Product compositions are reported for the FVP of 9-phenylanthracene (1), 2-bromobiphenyl (5), biphenyl (8), 1,10- diphenylanthracene (12), 9-(2-naphthyl)anthracene (17), and 9,9′- bianthracenyl (20). The experimental results have been used to evaluate four possible mechanistic pathways for the cleavage of aryl-aryl bonds under these conditions: (1) the 'explosion' of substituted phenyl radicals; (2) hydrogen atom attachment to an ipso-carbon atom of the biaryl followed by C-C bond cleavage; (3) direct homolysis; and (4) loss of a fragment as an aryne. None of these mechanisms by itself successfully accommodates all of the experimental facts. The data suggest that aryl-aryl bond cleavages under FVP conditions involve at least two different mechanistic pathways and that the relative contributions of the competing pathways probably vary from one biaryl to the next.
A new Suzuki-Heck-type coupling cascade: Indeno[1,2,3]-annelation of polycyclic aromatic hydrocarbons
Wegner, Hermann A.,Scott, Lawrence T.,De Meijere, Armin
, p. 883 - 887 (2007/10/03)
Under palladium catalysis, o-bromobenzeneboronic acid can be coupled with 1-bromonaphthalene (6) and with oligocyclic bromoarenes to furnish indeno-annelated polycyclic aromatic hydrocarbons 1-4 and 25 in a single operation in moderate to good yields (27-87%). Alternatively, o-dibromoarenes and 1,2-dibromocycloalkenes can be cross-coupled with 1-naphthaleneboronic acid under the same conditions to yield analogous products (6-87%), and indenocorannulene (19) can be prepared likewise in a single step from pinacol corannuleneboronate (18) (40%).
Thermolysis and photolysis of 1-substituted triptycenes. Divergent fragmentation pathways of the triptycyl skeleton
Tomioka, Hideo,Nakajima, Junichi
, p. 563 - 569 (2007/10/03)
While thermolysis of 1-benzyltriptycene 1a in the gas phase at 600°C/10-4 mmHg did not result in any appreciable decomposition, similar pyrolysis of compounds 1 bearing various substituents (X) at the benzyl methylene (1b-d) underwent smooth decomposition to give 8-benzylbenz[a]aceanthrylene 2. The reaction is explained in terms of homolysis of the C-X bond followed by triptycyl ring cleavage in the resulting benzyl radical 7. Generation of radical 7 in solution, however, did not result in a similar ring-opening reaction. Irradiation of compounds 1, on the other hand, afforded norcaradienes 3 almost exclusively, obviously as a result of di-π-methane rearrangement. No products resulting from a carbene species proposed to be involved in the di-π-methane reaction of triptycenes were detected. Thermolysis of compounds 3 gave not only compound 2 but also benz[a]aceanthrylene 4 and benz[a]indeno[1,2,3-cd]azulene 5 whose compositions were found to be sensitive to both the substituent (X) and the thermolysis temperature. Mechanisms of the reactions are discussed in terms of the relationship between the thermal and photochemical fragmentations.
