7334-33-0Relevant articles and documents
Azo synthesis meets molecular iodine catalysis
Rowshanpour, Rozhin,Dudding, Travis
, p. 7251 - 7256 (2021/02/26)
A metal-free synthetic protocol for azo compound formation by the direct oxidation of hydrazine HN-NH bonds to azo group functionality catalyzed by molecular iodine is disclosed. The strengths of this reactivity include rapid reaction times, low catalyst loadings, use of ambient dioxygen as a stoichiometric oxidant, and ease of experimental set-up and azo product isolation. Mechanistic studies and density functional theory computations offering insight into this reactivity, as well as the events leading to azo group formation are presented. Collectively, this study expands the potential of main-group element iodine as an inexpensive catalyst, while delivering a useful transformation for forming azo compounds.
Heterocoupling of Different Aryl Nitrenes to Produce Asymmetric Azoarenes Using Iron-Alkoxide Catalysis and Investigation of the Cis-Trans Isomerism of Selected Bulky Asymmetric Azoarenes
Groysman, Stanislav,Kurup, Sudheer S.,Wannipurage, Duleeka
, p. 3637 - 3644 (2021/11/12)
Heterocoupling of different aryl nitrenes (originating in organoazides) to produce asymmetric azoarenes using two different iron-alkoxide catalysts is reported. Fe(OCtBu2(3,5-Ph2C6H3))2(THF)2 was previously shown to catalyze the homocoupling of a variety of aryl nitrenes. While bulky nitrenes featuring ortho substituents were coupled more efficiently, coupling of the less bulky meta- and para-substituted aryl nitrenes was also demonstrated. In contrast, the iron(II) complex of a chelating bis(alkoxide) ligand, Fe[OO]Ph(THF)2, was previously shown to efficiently couple nonbulky aryl nitrenes lacking substituents in ortho positions. In the present work, we demonstrate that the combination of two different nitrenes (10 equiv overall, 5 equiv each) with Fe(OCtBu2(3,5-Ph2C6H3))2(THF)2 (10 mol %) produced a statistical or close to statistical distribution (25:25:50 for the two homocoupled products and the heterocoupled product, respectively) for various combinations containing one or two ortho alkyl substituents at one nitrene and a single ortho alkyl group at another. Surprisingly, the combination of Fe[OO]Ph(THF)2 with two different nonbulky organoazides was found to primarily catalyze the homocoupling of the resulting aryl nitrenes (21-49%), with a smaller proportion (～8-15%) of asymmetric product formation. Six different heterocoupled products featuring one or two alkyl groups in the ortho positions were isolated as a mixture of cis and trans isomers at room temperature and characterized by NMR spectroscopy, UV-vis spectroscopy, and high-resolution mass spectrometry. Following their isolation, cis-trans isomerism in these species was investigated. Heating the cis-trans mixture to 60 °C produced the trans isomer cleanly, while shining UV light on the cis-trans mixture significantly increased the amount of the cis isomer (up to 90%). The cis isomer was found to be relatively stable, exhibiting t1/2 values of approximately 10 days at room temperature.
Immobilized antimony species on magnetite: A novel and highly efficient magnetically reusable nanocatalyst for direct and gram-scale reductive-coupling of nitroarenes to azoarenes
Zeynizadeh, Behzad,Faraji, Fariba
, p. 13112 - 13121 (2019/05/10)
In this study, magnetic nanoparticles of Fe3O4@SbFx from the immobilization of SbF3 on magnetite were synthesized. The prepared nanocomposite system was then characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, vibrating sample magnetometry and inductively coupled plasma optical emission spectroscopy. Next, the catalytic activity of Fe3O4@SbFx MNPs was highlighted by one-pot reductive-coupling of aromatic nitro compounds to the corresponding azoarene materials with NaBH4. The reactions were carried out in refluxing EtOH within 6-25 min to afford the products in high yields. The reusability of the Sb-magnetite system was also studied for 6 consecutive cycles without significant loss of catalytic activity. This synthetic protocol provided several advantages in terms of introducing a novel catalytic system based on antimony species for direct and gram-scale preparation of azoarenes from nitroarenes, low loading of the nanocatalyst, mild reaction conditions, using ethanol as a green and economic solvent and high yield of the products.
