25179-49-1Relevant articles and documents
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.
Gold-catalyzed direct hydrogenative coupling of nitroarenes to synthesize aromatic azo compounds
Liu, Xiang,Li, Hai-Qian,Ye, Sen,Liu, Yong-Mei,He, He-Yong,Cao, Yong
supporting information, p. 7624 - 7628 (2014/08/05)
The azo linkage is a prominent chemical motif which has found numerous applications in materials science, pharmaceuticals, and agrochemicals. Described herein is a sustainable heterogeneous-gold-catalyzed synthesis of azo arenes. Available nitroarenes are deoxygenated and linked selectively by the formation of N-N bonds using molecular H2 without any external additives. As a result of a unique and remarkable synergy between the metal and support, a facile surface-mediated condensation of nitroso and hydroxylamine intermediates is enabled, and the desired transformation proceeds in a highly selective manner under mild reaction conditions. The protocol tolerates a large variety of functional groups and offers a general and versatile method for the environmentally friendly synthesis of symmetric or asymmetric aromatic azo compounds.
