Reversing Chemoselectivity: Simultaneous Positive and Negative Catalysis by Chemically Equivalent Rims of a Cucurbit[7]uril Host

Abstract

Enzyme catalysis has always been an inspiration and an unattainable goal for chemists due to features such as high specificity,selectivity,and efficiency.Here,wedisclose afeature neither common in enzymes nor ever described for enzyme mimics,b ut one that could prove crucial for the catalytic performance of the latter,n amely the ability to catalyze and inhibit two different reactions at the same time.R emarkably, this can be realized by two identical, spatially resolved catalytic sites.Inthe future,such asynchronized catalyst action could be used not only for controlling chemoselectivity,asinthe present case,but also for regulating other types of chemical reactivity.

Cucurbit[7]uril‐Catalyzed Controllable Pinacol Rearrangement with Activated Hydride Migration

“…General methods and materials. 1 H NMR (400 MHz), 19 F (376 M Hz), and 13 C NMR (100 MHz) were recorded on a JEOL JNM-ECZ400S NMR spectrometer with D 2 O and CDCl 3 as solvent. Chemical shifts of 1 H, 19 F and 13 C NMR spectra are reported in parts per million (ppm).…”

“…1 H NMR (400 MHz), 19 F (376 M Hz), and 13 C NMR (100 MHz) were recorded on a JEOL JNM-ECZ400S NMR spectrometer with D 2 O and CDCl 3 as solvent. Chemical shifts of 1 H, 19 F and 13 C NMR spectra are reported in parts per million (ppm). The residual solvent signals were used as references and the chemical shifts converted to the TMS scale (CDCl 3 : δ H = 7.26 ppm, δ C = 77.00 ppm; D 2 O: δ H = 4.79 ppm).…”

“…1,2-Diphenyl-ethanone (2 a): [23] 1 H NMR (400 MHz, CDCl 3 ) δ 8.03 (d, J = 7.8 Hz, 2H), 7.56 (t, J = 7.5 Hz, 1H), 7.47 (t, J = 7.6 Hz, 2H), 7.37-7.30 (m, 2H), 7.30-7.22 (m, 3H), 4.30 (s, 2H); 13 C NMR (100 MHz, CDCl 3 ) δ 197. 8, 136.7, 134.7, 133.3, 129.6, 128.9, 128.8, 128.7, 127.0, 45.7.…”

“…These distinctive features enabled Q[n]s to be effective on controlling reactivity and selectivity of chemical reactions. [9a,11-17] Q[n]s promote cycloaddition, [11] desilylation, [12] condensation, [13] oxidation, [14] hydrolysis, [15] esterification [16] and other organic reactions. [17] Herein, a new application of cucurbit[n]uril (Q [7], Scheme 1) for organic synthesis was explored.…”

Toward Understanding CB[7]-Based Supramolecular Diels-Alder Catalysis

“…Cucurbit [n]urils (CB[n], n = 5-8), are great supramolecular hosts, creating a microscopic environment while maintaining good solubility in water (Barrow et al, 2015). Besides participating in host-guest chemistry (Zhang et al, 2012;Wu et al, 2017Wu et al, , 2019Olesińska et al, 2019;Huang et al, 2020), they were successfully utilized in catalytic applications (Wang et al, 2011;Taylor et al, 2013;Zheng et al, 2015;Palma et al, 2017;Ren et al, 2018;Rad et al, 2019), surface chemistry (Wagner et al, 2020), and sensing and detection (Huang et al, 2012;Kasera et al, 2012;Biedermann et al, 2015;de Nijs et al, 2017de Nijs et al, , 2019.…”