Department of Chemistry, Wayne State University, 5101 Cass Ave., Detroit, MI 48202, USA.
Dalton Trans. 2022 Mar 22;51(12):4577-4589. doi: 10.1039/d2dt00228k.
Various valuable properties of azoarenes ("azo dyes"), including their vivid colors and their facile - photoisomerization, lead to their wide use in the chemical industry. As a result, ∼700 000 metric tons of azo dyes are produced each year. Most currently utilized synthetic methods towards azoarenes involve harsh reaction conditions and/or toxic reagents in stoichiometric amounts, which may affect selectivity and produce significant amounts of waste. An efficient alternative method towards this functional group includes transition metal catalyzed nitrene coupling. This method is generally more sustainable compared with most stoichiometric methods as it uses only catalytic amounts of co-reactants (metal catalysts), requires easily synthesizable organoazide precursors, and forms only dinitrogen as a by-product of catalysis. During the last decade, several catalytic systems were reported, and their reactivity was investigated. This perspective article will review these systems, focusing on various nitrene coupling mechanisms, and the substrate scope for each system. Particular attention will be devoted to the iron-alkoxide catalytic systems investigated in the PI's laboratory. The design and structural features of several generations of iron bis(alkoxide) complexes will be discussed, followed by the structure-activity studies of these catalysts in nitrene homo- and heterocoupling.
偶氮芳烃（“偶氮染料”）具有各种有价值的性质，包括鲜艳的颜色和易于光异构化，这导致它们在化学工业中的广泛应用。因此，每年大约生产 70 万吨偶氮染料。目前大多数用于偶氮芳烃的合成方法涉及苛刻的反应条件和/或化学计量的有毒试剂，这可能会影响选择性并产生大量废物。一种有效的替代方法是过渡金属催化的氮烯偶联。与大多数化学计量方法相比，这种方法通常更具可持续性，因为它仅使用催化量的共反应物（金属催化剂），需要可容易合成的有机叠氮化物前体，并且仅形成催化的副产物氮气。在过去的十年中，已经报道了几种催化体系，并研究了它们的反应性。本文综述了这些体系，重点讨论了各种氮烯偶联机制以及每个体系的底物范围。特别关注 PI 实验室研究的铁醇盐催化体系。将讨论几代铁双（醇盐）配合物的设计和结构特征，然后讨论这些催化剂在氮烯同偶联和异偶联中的结构-活性研究。
