Close Amide NH•••F Hydrogen Bonding Interactions in 1,8-Disubstituted Naphthalenes
Close Amide NH•••F Hydrogen Bonding Interactions in 1,8-Disubstituted Naphthalenes
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DOI：
10.1021/acs.joc.0c00553
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发表时间：
2020-05-01
影响因子：
3.6
通讯作者：
Lectka, Thomas
中科院分区：
文献类型：
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作者：
Kazim, Muhammad;Siegler, Maxime A.;Lectka, Thomas
在这篇文章中，我们提出了一系列的N-（8-氟萘-1-基）苯甲酰胺衍生物的设计，以最大限度地提高酰胺-NH中心点F氢键相互作用。IR和NMR光谱的组合表明NH伸缩频率的高能量位移和取代基的吸电子性质之间的线性相关性，与DFT计算预测的趋势一致。此外，当苯甲酰胺衍生物被三氟乙酰胺取代时，观察到氢键的极限情况，导致NH伸缩频率额外红移44 cm（-1）。最重要的是，H-1-F-19耦合常数在这个系列中是最大的酰胺-NH-F相互作用的测量。X射线晶体学揭示了这些衍生物中萘环的面对面排列，部分原因是NH中心点中心点F氢键。该基序还决定了在晶体结构中形成由堆叠的萘环组成的片，这与未氟化的类似物相反，其中NH中心点中心点OC氢键相互作用迫使苯甲酰胺和萘环参与T形π-π相互作用。此外，三氟乙酰胺衍生物中的NH质子参与其晶体结构中的扩展H-键相互作用。
In this note, we present a series of N-(8-fluoronaphthalen-1-yl)benzamide derivatives designed to maximize amide-NH center dot center dot center dot F hydrogen bond interactions therein. A combination of IR and NMR spectroscopy indicates a linear correlation between the high energy shift in NH stretching frequency and the electron withdrawing nature of the substituent, consistent with the trend predicted by DFT calculations. Additionally, a limiting case of hydrogen bonding is observed when the benzamide derivatives are replaced with trifluoroacetamide, causing an additional red shift of 44 cm(-1) in the NH stretching frequency. Most importantly, H-1-F-19 coupling constants in this series are among the largest measured for amide-NH-F interactions. X-ray crystallography reveals face-to-face alignment of naphthalene rings in these derivatives resulting in part from the NH center dot center dot center dot F hydrogen bonds. This motif also dictates the formation of sheets composed of stacked naphthalene rings in the crystal structure as opposed to unfluorinated analogues wherein NH center dot center dot center dot OC hydrogen-bonding interactions force benzamide and naphthalene rings to engage in T-shaped pi-pi interactions instead. Additionally, the NH proton in the trifluoroacetamide derivative engages in extended H-bond interactions in its crystal structure.