[(Dpepphos) (bcp) Cu]PF6: 一种通用的、广泛适用的铜基光氧催化剂
Summary
本文提出了合成 [(Dpepphos) (bcp) Cu] PF6的详细和一般的协议, 这是一种普通的铜基光多克斯催化剂, 并用于合成化学中的 c-h 键在 (异种) 芳烃和自由基中的直接芳基化有机卤化物的环化。
Abstract
我们的小组最近报告了使用 [(Dpepphos) (bcp) CU] PF6作为一般铜基光电多克斯催化剂, 证明有效地促进了多种有机卤化物的活化, 包括未激活的卤化物。然后, 它们可以参与各种自由基的转变, 如还原和环化反应, 以及几种 (异质) 芳烃的直接芳基化。这些转变提供了一个直接的访问一系列感兴趣的合成化学小分子, 以及生物活性天然产品。总之, [(Dpepphos) (bcp) CU] PF6是一种方便的光数催化剂, 它似乎是一种极具吸引力、廉价和互补的替代品, 取代了最先进的基于虹膜和红宝石的光华多波催化剂。在这里, 我们报告了一个详细的协议, 用于合成 [(dpephos) (Bcp) CU]pf 6, 以及核磁共振和光谱特征, 我们说明了它在合成化学中的应用, 用于 (杂化) 芳烃和自由基环化。有机卤化物。特别是, n-甲基吡咯与 4-碘苯并腈的直接芳化, 可承受 4-(1-甲基-1 h-吡咯-2-酰基) 苯并腈的自由环化和n-苯甲基-n-[(2-碘喹诺林 3-基) 甲基化。氰氨化物提供天然产品罗托宁 a 是详细的。简要讨论了这种铜基光毒催化剂的范围和局限性。
Introduction
在合成化学中, 自由基转化已经被认为是非常有效的途径, 而合成化学往往是基于阳离子、阴离子或环环过程1的转化的补充。虽然对各种转化特别有希望, 但基于激进的化学长期以来一直没有得到充分利用, 主要原因是需要剧毒试剂, 这大大限制了其吸引力。此外, 自由基过程长期以来一直被认为是与区域和立体选择性控制水平低有关的转变, 或导致广泛的二聚和/或聚合问题。
最近制定了替代战略, 以促进自由基物种的产生和更好地控制其反应性。其中, 光合毒素催化已成为最有力的方法之一, 因为它允许使用光响应化合物, 即光氏杆菌催化剂和可见光照射2, 3,方便地生成自由基物种.可见光本身确实能够促进光数催化剂激发状态的种群, 因此, 光数催化剂既能成为一种更强的还原剂, 也能成为其相应的基态。这些增强的氧化还原特性使得单电子转移过程在激发态的温和条件下成为可能, 在基态条件下是不可行的。在过去的十年里, 可见光光合牛催化已成为有机合成中一种有吸引力和强大的技术, 并使许多基于自由基中间体的非常高效和选择性的转化得以发展在可持续、温和和方便用户的条件下产生。
虽然迄今报告的大多数光比多克工艺主要是使用以锂和红宝石为基础的光合酶催化剂, 以及一些有机染料, 如吡咯和丙烯衍生物4, 但对更便宜的替代品的要求仍然很高用于开发工业应用中感兴趣的互补工艺。在这方面, 使用基于铜的光影毒催化剂似乎特别吸引人, 因为它们不仅更便宜, 而且还提供了激活更广泛和/或不同范围的基板的机会, 从而开辟了新的前景。光合催化5,6,7, 8.尽管库塔尔9号、米塔尼10和绍瓦奇11组报道了一些有希望的早期作品, 但光可活动铜质综合体几乎没有用于光毒杆菌催化, 很可能是因为它们与以和为基础的同源物相比, 短命的兴奋状态。最近, 彼得斯和傅做出了显著的贡献,12,13, 14, 15, reiser16,17,18 ,19,20组和其他组21,22,23, 24,25显然已经引起了人们的注意, 铜基光合酶催化剂, 并证明了他们的独特的潜力。
作为我们最近对铜催化自由基工艺的兴趣的一部分26,27, 我们最近报告了一个普遍和广泛适用的铜基光影量催化剂, [(dpephos) (bcp) cu] pf6 (dpephos: bis[(2-苯醚;bcp: 基波林), 它被证明是特别有效的激活有机卤化物在可见光照射下 (图 1a)28,29,30。在可见光照射下, 在作为牺牲还原剂的胺存在的情况下, 大量未活化的芳基和烷基卤化物被催化量 [(Dpepphos) (Bcp) Cu] pf]6 (因此参与) 很容易激活在各种彻底的转变中, 包括几种富含电子 (异种) 的芳烃的还原、环切和直接芳基化。此外, [(Dpepphos) (bcp) Cu] PF6也已被证明成功地促进了动力学剂和氰化物的光诱导的自由基多米诺骨牌化, 提供了一个有效和直接的访问复杂的三、四联和五环氮杂环是各种天然产物的核心结构。这一策略使迷他汀、罗托宁 a 和脱氧血管素的天然产物具有抗癌、抗菌、抗炎和抗抑郁活性, 从而有效地合成了。这些转换如图 1C所示。从机械角度来看, 用 [(Dpepphos) (Bcp) cu] PF6光诱导活化是通过一个罕见的 Cu(I)/Cu(I)*/Cu(0) 催化循环进行的, 这一点已得到广泛的机械和光物理研究的证实。特别是, 激发的基态 [(Dpepphos) (bcp) Cu] pf 6 [cu (i)] 后, 由可见光照射导致形成相应的激发复合体 [(dpepphos) (bcp) cu] pf6* [cu (i) *], 然后减少由牺牲胺产生相应的 [(Dpepphos) (bcp) cu] pf6 [Cu(0)]。这种 Cu(0) 中间体还原到足以减少各种有机卤化物的碳-卤素键, 从而产生相应的自由基, 然后可以参与上述转变, 同时再生启动(图 1 b)。
在下一节中, 我们首先描述了合成光电可的协议 [(Dpepphos) (bcp) Cu] PF6 (其核磁共振和光谱特征在代表性结果部分中介绍)。合成是简单的, 特别方便, 只需要添加1个相当于 Dpepphos 和1个相当于 bcp 的六氯甲烷中的四乙酰基二腈铜 (I) 溶液中的 bcp。然后通过二乙醚的沉淀分离所需的 [(dpepphos) (Bcp) cu] PF 6 , 并且可以很容易地在多克尺度上获得 (图 2 a)。重要的是, 隔离的铜复合体对氧气和水分不是特别敏感, 因此可以方便地处理, 除了远离光线存储之外, 没有其他具体的预防措施。
其次, 我们描述了使用 [(Dpepphos) (Bcp) cu] PF6激活有机卤化物的协议, 重点是两个不同的转变。第一反应是用催化量 [(Dpepphos) (Bcp) cu] PF 6 作为光角上克催化剂, 二环己基异丁胺作为牺牲还原剂和钾, 用 4-碘苯酮腈直接酰化作为在420纳米辐照下的碱基 (图 2B)。第二反应是n-苯甲酰-n-[(2-碘喹啉-3-基) 甲基] 氰氨化的自由基化, 使用相同的催化剂和牺牲还原剂, 其环化直接导致罗托宁 a, 一种天然产品显示有趣的抗癌活动 (图 2c)。为这两个转换提供了详细的协议。
Protocol
Representative Results
Discussion
[(Dpepphos) (bcp) Cu] PF6的合成
[(DPEPhos) (bcp) cu] PF6的合成通常使用干二氯甲烷 (使用前蒸馏) 和氩下进行, 以确保最高的产量、纯度和良好的重现性。如议定书所述, [(Dpepphos) (bcp) cu] PF6的合成可以用普通的二氯甲烷进行 (99.8%)在空气中, 效率可变。事实上, 虽然在氩下使用普通的二氯甲烷具有同样的效率 (产量为 89%), 但在空气下使用蒸馏二氯甲烷只能提供所需的复合…
Divulgations
The authors have nothing to disclose.
Acknowledgements
这项工作得到了布鲁塞尔自由大学 (ULB)、Wallone-bruxleles 联合会 (ARC 合作者 2014-2019)、Innoviris (photocop 项目) 和咖啡和工业和工程部行动 CM1202 的支持。H. b. 承认 “勒彻切之山” 为研究生奖学金。C. t. 承认《科学研究基金会》 (FNRS) 的研究金。
Materials
| Material | |||
| Bathocuproine (bcp) | Acros | 161340010 | |
| Acetonitrile, 99.9+ | Acros | 326811000 | |
| Celite 545 | Acros | 349670025 | |
| Bis[(2-diphenylphosphino)phenyl] ether (DPEphos) | Acros | 383370050 | |
| Calcium hydride | Acros | C/1620/48 | |
| Dichloromethane, 99.8% | Fisher Chemical | D/1852/25 | |
| Dietyl ether, >= 99% | Fisher Chemical | D/2400/MS21 | |
| Ethyl acetate | Fisher Chemical | E/0900/25 | |
| N-Methylpyrrole, 99% | Sigma Aldrich | M78801 | |
| 4-Iodobenzonitrile, 98% | Combi-Blocks | OR-3151 | |
| Petroleum ether (40-60 °) | Fisher Chemical | P/1760/25 | |
| Potassium carbonate, anhydrous | Fisher Chemical | P/4120/60 | |
| Tetrakisacetonitrile copper(I) hexafluorophosphate, 97% | Sigma Aldrich | 346276 | |
| Equipment | |||
| 1H and 13C NMR spectrometer | Bruker | Avance 300 Spectrometer | |
| 1H and 13C NMR spectrometer | Varian | VNMRS 400 Spectrometer | |
| 420 nm light tubes | Luzchem | LZC-420 | |
| Blue LEDs lamp | Kessil | H150-Blue | |
| Blue LEDs strips | Eglo | 92065 | |
| Photochemistry Device PhotoRedOx Box | Hepatochem | HCK1006-01-016 | |
| Photoreactor | Luzchem | CCP-4V | |
| Spectrofluorimeter | Shimadzu | RF-5301PC | |
| UV/Vis spectrometer | Perkin Elmer | Lambda 40 |
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