Tetracyclo(2,7-carbazole)s: Diatropicity and Paratropicity of Inner Regions of Nanohoops

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• 作者：Yasuhiro Kuroda ; Youichi Sakamoto ; Toshiyasu Suzuki ; Eiichi Kayahara ; Shigeru Yamago
• 刊名：Journal of Organic Chemistry
• 出版年：2016
• 出版时间：April 15, 2016
• 年：2016
• 卷：81
• 期：8
• 页码：3356-3363
• 全文大小：647K
• 年卷期：0
• ISSN：1520-6904

文摘

Three N-substituted tetracyclo(2,7-carbazole)s were synthesized to investigate the inner regions of nanohoops. One compound has a 5,5-dimethylnonane bridge between two neighboring anti-carbazoles, which can be used as covalently bonded “methane probes”. These probes near the ring center are strongly shielded by local ring currents and exhibit a singlet at δ = −2.70 ppm in ¹H NMR. To visualize local and macrocyclic ring currents separately, we drew nucleus-independent chemical shift contour maps of tetracyclo(9-methyl-2,7-carbazole) and [n]cycloparaphenylenes (CPPs). Local ring currents make the interior diatropic, and paratropic regions exist only outside the ring. Macrocyclic ring currents in [5]CPP to [7]CPP generate deshielding cones, which are typical of antiaromatic [4n]annulenes.