Whitaker Tessa, Tuttle Robert, Thai Jonathan E, Schwarz Madeline C R, Reynolds Melissa M
Department of Chemistry, Colorado State University, 1801 Campus Delivery, Fort Collins, Colorado 80523, United States.
School of Biomedical Engineering, Colorado State University, 1376 Campus Delivery, Fort Collins, Colorado 80523, United States.
ACS Appl Mater Interfaces. 2024 May 1;16(17):22641-22647. doi: 10.1021/acsami.4c00988. Epub 2024 Apr 22.
The copper-based metal-organic framework (MOF), CuBTC (where HBTC = benzene-1,3,5-tricarboxylate), has been reported as a reusable heterogeneous catalyst for the Friedländer synthesis of substituted quinolines, which are desirable targets in the pharmaceutical industry. Because of this application, we further investigated the CuBTC-catalyzed Friedländer synthesis of 3-acetyl-2-methyl-4-phenylquinoline. CuBTC was synthesized in-house and used as a catalyst for the Friedländer synthesis. Fresh and used CuBTC were analyzed using scanning electron microscopy (SEM), powder X-ray diffraction (pXRD), and X-ray photoelectron spectroscopy (XPS). The used CuBTC shows structural breakdown in pXRD patterns and SEM images. Despite the structural breakdown, the desired product, 3-acetyl-2-methyl-4-phenylquinoline, is still produced in a moderate yield (76.3% ± 0.2), as confirmed via time-of-flight mass spectrometry and nuclear magnetic resonance spectroscopy. Inductively coupled plasma atomic emission spectroscopy of the recovered supernatant solution indicates the presence of copper(II) ions in solution. Thus, we hypothesized that the standard Friedländer conditions may degrade the CuBTC framework, resulting in copper(II) ions in solution. Control experiments with copper(II) from Cu(NO)·3HO catalyzes the Friedländer reaction in yields (75.6% ± 0.1) equal to that of the CuBTC MOF. Overall, our findings suggest that CuBTC acts as a copper(II) source, and the copper(II) ions originating from the CuBTC MOF are responsible for the observed catalysis.
据报道，铜基金属有机框架材料（MOF）CuBTC（其中HBTC = 苯-1,3,5-三甲酸）是一种可重复使用的多相催化剂，用于取代喹啉的Friedländer合成，而喹啉是制药行业中理想的目标产物。基于此应用，我们进一步研究了CuBTC催化的3-乙酰基-2-甲基-4-苯基喹啉的Friedländer合成。CuBTC在内部合成，并用作Friedländer合成的催化剂。使用扫描电子显微镜（SEM）、粉末X射线衍射（pXRD）和X射线光电子能谱（XPS）对新鲜和使用过的CuBTC进行了分析。使用过的CuBTC在pXRD图谱和SEM图像中显示出结构破坏。尽管结构遭到破坏，但通过飞行时间质谱和核磁共振光谱证实，仍以中等产率（76.3%±0.2）生成了所需产物3-乙酰基-2-甲基-4-苯基喹啉。对回收的上清液进行电感耦合等离子体原子发射光谱分析表明溶液中存在铜（II）离子。因此，我们推测标准的Friedländer反应条件可能会使CuBTC框架降解，从而在溶液中产生铜（II）离子。用Cu(NO)·3HO中的铜（II）进行的对照实验催化Friedländer反应的产率（75.6%±0.1）与CuBTC MOF的产率相当。总体而言，我们的研究结果表明，CuBTC充当铜（II）源，源自CuBTC MOF的铜（II）离子是观察到的催化作用的原因。
