19227-07-7Relevant articles and documents
Stereochemistry, Stereodynamics, and Redox and Complexation Behaviors of 2,2′-Diaryl-1,1′-Biazulenes
Tsuchiya, Takahiro,Katsuoka, Yuka,Yoza, Kenji,Sato, Hiroyasu,Mazaki, Yasuhiro
, (2019)
2,2′-Diaryl-1,1′-biazulenes were synthesized and electronic communication between the azulene subunits was suggested based on redox measurements. The linkage of azulene at the 1-position also appeared to increase the HOMO levels. In addition, cyclic voltammetry measurements of 2-arylazulenes showed a return peak associated with the oxidation, which was not observed for azulene. The stabilization of the single-electron oxidant may be due to the SOMO-HOMO energy inversion phenomenon. X-ray crystallography of the azulene dimers revealed that this species possessed a syn-type structure in which both aryl groups in the 2-positions formed π-stacks. The twisted structure was indicated to be in the (R)- or (S)-configuration for all molecules in the unit cell. Spontaneous resolution was also shown. Furthermore, from the solid circular dichroism (CD) spectral measurements, the relationship between the absolute configuration of the molecules and the CD spectra was determined. A racemization rotational barrier of ca. 27 kcal mol?1 was calculated. Moreover, the pyridylazulene dimer cyclized upon reaction with PdCl2 to form a 3 : 3 complex, in which the biazulene units cyclized to give ratios between the (R)- and (S)-forms of either 2 : 1 or 1 : 2.
Iridium-catalyzed dehydrogenative silylation of azulenes based on regioselective C-H bond activation
Murai, Masahito,Takami, Keishi,Takeshima, Hirotaka,Takai, Kazuhiko
, p. 1798 - 1801 (2015)
Use of an iridium catalyst allowed the efficient dehydrogenative functionalization of C-H bonds of azulenes with the production of hydrogen as the sole byproduct. The reaction occurred with excellent chemo- and regioselectivities to provide 2-silylazulene
Carboxylic Acid Directed C-H Arylation of Azulene
Png, Zhuang Mao,Tam, Teck Lip Dexter,Xu, Jianwei
supporting information, p. 5009 - 5013 (2020/07/04)
The first example of directed C-H activation for azulene is reported. A variety of 2-arylazulenes are obtainable exclusively from 1-azulene carboxylic acids, with yields of up to 82percent. Some heteroaryl groups such as pyridine and thiophene are also tolerated in the reaction. The efficacy of the reaction is found to be highly dependent on the conditions, with a phosphate base and a bulky carboxylic acid being key additives.
Bicyclo[6.3.0]undecapentaenyl anion: The next higher homolog of the indenyl anion with exceptionally large ion-pairing effects on its tropicity
Ozoe, Hiroaki,Uno, Yasutaka,Kitamura, Chitoshi,Kurata, Hiroyuki,Oda, Masaji,Jones Jr., John W.,Scott, Lawrence T.,Kawase, Takeshi
, p. 893 - 900 (2014/03/21)
The title anion 1 was generated as a fairly thermally stable species in tetrahydrofuran (THF) and dimethylsulfoxide (DMSO) by the action of several bases (sodium hydride, potassium hydride, lithium diisopropylamide, and lithium hexamethyldisilazide) with appropriate bicyclo[6.3.0]undecapentaenes. Variable-temperature 1H NMR spectra of 1×Li+ in [D8]THF reveal that the anion exhibits exceptionally large ion-pairing effects; proton chemical shifts vary by more than 1 ppm as a function of ion-pairing conditions. Thus, anion 1, in a contact ion pair (Li+ at ambient temperature in THF), behaves as an aromatic cyclopentadienyl anion that is perturbed only slightly by the electronic effects of a paramagnetic cyclooctatetraene (COT), whereas 1 in a separated ion pair (Li+ at low temperatures in THF or at ambient temperature in DMSO) behaves as an overall paratropic species with a 12 π-electron periphery. 13C NMR spectroscopy indicates no major skeletal rearrangement and only small variations of the electron density. The variable tropicity of 1 can be ascribed to small conformational changes of the molecule. In addition to its unusual, tunable tropicity, anion 1 can also serve as a versatile building block for the synthesis of cyclopentanoid conjugated systems fused to a fully unsaturated eight-membered ring. A theoretical calculation predicts that the 10-position of 1 should have the highest electron density. In agreement with this prediction, the reactions of 1 with electrophiles occur predominantly at the 10-position. The corresponding ferrocene, two fulvenes, two diazo derivatives, and a COT-fused azulene were obtained by the reactions of 1 with appropriate electrophiles. Split personality: The bicyclo[6.3.0]undecapentaenyl anion, which is the next higher homolog of the indenyl anion, behaves as an aromatic cyclopentadienide ion slightly perturbed by the effects of a paramagnetic cyclooctatetraene in a contact ion pair, whereas in a solvent-separated ion pair it is an overall paratropic species owing to a 12 π-electron periphery (see picture). Copyright
