642-32-0Relevant academic research and scientific papers
Novel synthetic route to octasubstituted naphthalenes from four alkynes and one olefin unit via zirconacyclopentadienes and 1,2-Diiodo-3,4,5,6- tetraalkylbenzene
Zhou, Xin,Li, Zhiping,Wang, Hui,Kitamura, Masanori,Kanno, Ken-Ichiro,Nakajima, Kiyohiko,Takahashi, Tamotsu
, p. 4559 - 4562 (2007/10/03)
1,2,3,4-Tetrasubstituted benzene derivatives were prepared by the reaction of zirconacyclopentadienes with vinyl bromide in the presence of NiCl 2(PPh3)2. 1,2-Diiodo-3,4,5,6-tetraalkylbenzenes were formed by treatment of 1,2,3,4-tetraalkylbenzenes with iodine and periodic acid in the presence of a catalytic amount of sulfuric acid. Reaction of the 1,2-diiodo-3,4,5,6-tetraalkylbenzenes with zirconacyclopentadienes in the presence of a stoichiometric amount of CuCl gave sterically crowded octasubstituted naphthalenes in moderate yields.
Unprecedented double C-C bond cleavage of a cyclopentadienyl ligand
Xi, Zhenfeng,Sato, Kimihiko,Gao, Ye,Lu, Jianming,Takahashi, Tamotsu
, p. 9568 - 9569 (2007/10/03)
Double C-C bond cleavage of a cyclopentadienyl ligand proceeded to titanacyclopentadienes when 2 equiv of nitriles were added and the resulting two-carbon unit and three-carbon unit were converted into a benzene derivative and a pyridine derivative, respectively, in one-pot. Copyright
Preparation and conformation of octaethylbiphenylene
Taha,Marks,Gottlieb,Biali
, p. 8621 - 8628 (2007/10/03)
Dimerization of tetraethylbenzyne (generated by reaction of 1,2-dibromo-3,4,5,6-tetraethylbenzene (8) with 1 equiv of BuLi) afforded in low yield octaethylbiphenylene (3), together with a major product which was characterized as 2,3,4,5,3',4',5'-heptaethyl-2'-vinylbiphenyl (9). X-ray diffraction indicates that biphenylene 3 adopts in the crystal a conformation of approximate C(2h) symmetry with the ethyl groups within each phenylene ring arranged in an alternated up-down fashion. Notably, pairs of vicinal ethyl groups located at peri positions are oriented in a syn arrangement in the crystal. Low temperature NMR spectroscopy is consistent with the presence in solution of either the crystal conformation or a fully alternated conformation lacking any syn interaction. Molecular mechanics (MM3), semiempirical (AM1, PM3), and ab initio calculations indicate that the crystal conformation is a high energy form, and that the lowest energy conformation is the fully alternated form. The topomerization barrier of the methylene protons of the ethyl groups of 3 is 9.4 ± 0.1 kcal mol-1, which is between the rotational barriers of 8 and 1,2,3,4-tetraethylbenzene 7 (9.9 ± 0.1 and 8.2 ± 0.1 kcal mol-1, respectively). The similarity in rotational barriers suggests that a given tetraethylphenylene subunit does not markedly affect the rotational barrier of the ethyl groups of the other subunit.
Process for producing pyromellitic dianhydride
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, (2008/06/13)
Pyromellitic dianhydride, useful as raw material for the manufacture of polyimides, is prepared in high yield and purity by the reaction of benzene derivatives such as ethylbenzene, diethylbenzenes, and triethylbenzenes with an ethylating agent in the presence of a Friedel-Crafts catalyst, the separation of tetraethylbenzenes from the reaction products by distillation, the separation of 1,2,4,5-tetraethylbenzene from other tetraethyl benzenes by differential centrifugal precipitation at -10 to -30 degrees Celsius, and the catalytic vapor-phase oxidation of tetraethyl benzenes, using a catalyst containing vanadium pentoxide and titanium dioxide.
