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
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
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DOI：
10.1021/acs.organomet.1c00490
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发表时间：
2021-11
期刊：
影响因子：
2.8
通讯作者：
Duleeka C. Wannipurage;Sudheer S. Kurup;Stanislav Groysman
中科院分区：
文献类型：
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作者：
Duleeka C. Wannipurage;Sudheer S. Kurup;Stanislav Groysman
本文报道了两种不同的铁醇盐催化剂用于芳基氮烯（有机叠氮化合物）的杂偶联制备不对称偶氮芳烃的反应。Fe（OCtBu 2（3，5-Ph 2C 6 H3））2（THF）2以前被证明催化各种芳基氮烯的均偶联。虽然具有邻位取代基的大体积氮烯更有效地偶联，但也证明了较小体积的Meta位和对位取代的芳基氮烯的偶联。与此相反，铁（II）络合物的chelatingbis（醇盐）配体，Fe[OO]Ph（THF）2，以前被证明有效地耦合非庞大的芳基氮烯缺乏取代基的邻位。在本工作中，我们证明了两种不同的氮烯（10当量的整体，5当量）与Fe（OCtBu 2（3，5-Ph 2C 6 H3））2（THF）2（10摩尔%）的组合产生的统计或接近统计分布（25：25：50的两个homocoupled产品和heterocoupled产品，分别）的各种组合含有一个或两个邻位烷基取代基在一个氮烯和一个单一的邻位烷基在另一个。令人惊讶的是，发现Fe[OO]Ph（THF）2与两种不同的非大体积有机叠氮化物的组合主要催化所得芳基氮烯的均偶联（21-49%），具有较小比例的不对称产物形成（0.88 -15%）。六个不同的杂耦合产品具有一个或两个烷基在邻位分离的顺式和反式异构体的混合物在室温下，其特征在于通过NMR光谱，紫外-可见光谱，和高分辨率质谱。分离后，研究了这些物种的顺反异构现象。将顺式-反式混合物加热到60 °C，干净地产生反式异构体，而在顺式-反式混合物上照射紫外线，显著增加了顺式异构体的量（高达90%）。顺式异构体被发现是相对稳定的，在室温下约10天的t1/2值。
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)2was 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 chelatingbis(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)2with 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, exhibitingt1/2values of approximately 10 days at room temperature.