29418-22-2Relevant academic research and scientific papers
Aromatic amine oxidation process for preparing aromatic azobenzene method
-
Paragraph 0024; 0026-0027, (2017/10/11)
The invention relates to a method for preparing an aromatic azo compound by utilizing aromatic amine oxidation. In the method, air or oxygen serves as an oxygen source, and under the effect of a catalyst, aromatic amine is oxidized into the aromatic azo compound. The method is high in oxidization efficiency and product yield; the air or the oxygen serves as the oxygen source, and the method is economical and environmentally friendly. The product and the catalyst can be separated easily, and the aftertreatment is simple. The catalyst is easy to reuse, and the method has very good application prospect.
Palladium-Catalyzed Carbonylative Cyclization of Azoarenes
Wang, Zechao,Yin, Zhiping,Zhu, Fengxiang,Li, Yahui,Wu, Xiao-Feng
, p. 3637 - 3640 (2017/10/13)
In this communication, we established an interesting palladium-catalyzed carbonylation protocol for the intramolecular cyclization of azoarenes. With Mo(CO)6 as the solid CO source and through C(sp2)?H bond activation, a series of azoarenes were transformed into the corresponding 2-arylindazolones in moderate to good yields. Notably, not only symmetrical azoarenes, but also unsymmetrical substrates underwent the reaction with excellent regioselectivity.
Oxidative coupling of anilines to azobenzenes using heterogeneous manganese oxide catalysts
Wang, Min,Ma, Jiping,Yu, Miao,Zhang, Zhe,Wang, Feng
, p. 1940 - 1945 (2016/04/05)
We herein report the transition metal oxide-catalyzed synthesis of azobenzenes through the oxidative coupling of anilines. An octahedral molecular sieve of manganese oxide, OMS-2, exhibited the best activity and selectivity. Nine examples of symmetric azobenzenes and twenty unsymmetric ones were synthesized with 62-99% conversion and 64-99% selectivity. In the aniline cross-coupling reactions, the difference of the Hammett constants of two substituted groups (Δσ) determines the selectivity to unsymmetric azobenzenes, which are the major products at Δσ 0.32. In-depth studies reveal that the surface defect sites of the mixed-valence manganese oxide play a key role in facilitating electron transfer and activating molecular oxygen. The single-electron transfer (SET) reaction mechanism is proposed based on electron paramagnetic resonance and X-ray powder diffraction characterization.
High-Yield Lithiation of Azobenzenes by Tin-Lithium Exchange
Strueben, Jan,Lipfert, Matthias,Springer, Jan-Ole,Gould, Colin A.,Gates, Paul J.,S?nnichsen, Frank D.,Staubitz, Anne
, p. 11165 - 11173 (2015/11/10)
The lithiation of halogenated azobenzenes by halogen-lithium exchange commonly leads to substantial degradation of the azo group to give hydrazine derivatives besides the desired aryl lithium species. Yields of quenching reactions with electrophiles are therefore low. This work shows that a transmetalation reaction of easily accessible stannylated azobenzenes with methyllithium leads to a near-quantitative lithiation of azobenzenes in para, meta, and ortho positions. To investigate the scope of the reaction, various lithiated azobenzenes were quenched with a variety of electrophiles. Furthermore, mechanistic 119Sn NMR spectroscopic studies on the formation of lithiated azobenzenes are presented. A tin ate complex of the azobenzene was detected and characterized at low temperature.
Aryliminodimagnesium Reagents. XIV. Reactions with Nitrobenzenes Having Electronegative ortho-Substituents. Effects of Reaction Conditions on Condensation, Replacement, and Substitution
Okubo, Masao,Inatomi, Yoshito,Taniguchi, Naoki,Imamura, Kaori
, p. 3581 - 3586 (2007/10/02)
In reactions of ArN(MgBr)2 with o-MeO- and o-halo-substituted nitrobenzenes, types and yields of products were different from those in its reactions with m- and p-substituted substrates.Condensation (leading to unsymmetrical azoxy- and azobenzenes), o-substituent replacement, and nuclear substitution took place.Relative yields of products were greatly affected by substituents and reaction conditions. o-MeO and o-F favor replacement, while o-Cl, o-Br, and o-I favor substitution.Replacement and/or substitution predominate when small molar excess of reagent and low concentration are used, while condensation predominates when large molar excess of reagent and high concentration are used, which phenomenon is mechanistically discussed.
