216979-52-1Relevant articles and documents
The cobalt-way to heterophenylenes: Syntheses of 2-thianorbiphenylenes, monoazabiphenylenes, and linear 1-aza[3]phenylene {biphenyleno[2,3-a] cyclobuta[1,2- b ]pyridine}
Engelhardt, Verena,Garcia, J. Gabriel,Hubaud, Aude A.,Lyssenko, Konstantin A.,Spyroudis, Spyros,Timofeeva, Tatiana V.,Tongwa, Paul,Vollhardt, K. Peter C.
, p. 280 - 284 (2011/04/16)
CpCo(CO)2 catalyzes the cocyclization of ortho- diethynylthiophenes and -pyridines with alkynes to construct the corresponding thia- and azaphenylenes. This strategy is applied to the synthesis of linear 1-aza[3]phenylene, the first higher heterophenylene. Georg Thieme Verlag Stuttgart.
Rapid Bergman cyclization of 1,2-diethynylheteroarenes
Kim, Chang-Sik,Russell
, p. 8229 - 8234 (2007/10/03)
The synthesis and cyclization of acyclic quinoxaline, pyridine, and pyrimidine enediynes (1-3) are described. These compounds were prepared using palladium(0) coupling of trimethylsilyl acetylene to o-dihalo- or o- halotriflic heteroarenes. All compounds were prepared in modest to good yields. The enediynes prepared were shown to undergo Bergman cyclization. Kinetics over a minimum of 3 half-lives were used to construct ]Arrhenius plots. Pyrimidine 3 was found to have an activation energy of 16.1 kcal/mol. Cyclization of the closest known aromatic analogue, o-diethynylbenzene (15), has E(a) = 25.1 kcal/mol (Grissom, J. W.; Calkins, T. L.; McMillen, H. A.; Jiang, Y. J. Org. Chem. 1994, 59, 5833-5835). Pyridine 2 and quinoxaline 1 gave activation energies of 21.5 and 33.6 kcal/mol, respectively. The results illustrate that heteroarenes can be used to activate Bergman cyclization. We expect these compounds to play an important role in furthering the understanding of Bergman cyclization and in aiding the development of new biologically significant enediynes.
