Chem. Phys. 132, 154104 (2010). extension of CCSD(T) with higher excitations would probably also deepen the NO–H2 potential well by a similar amount. The deeper well in the F12 potential, which caused the resonances from this potential to agree better with our experimental data, would then be a fortuitous compensation for the fact that we had to restrict our- selves to potentials computed at the CCSD(T) level.
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Chem. Phys. 146, 114301 (2017). NATURE CHEMISTRY | VOL 10 | APRIL 2018 | 435–440 | xxx.xxxxxx.xxx/xxxxxxxxxxxxxxx 439 ARTICLES NATURE CHEMISTRY Acknowledgements The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013)/ ERC grant agreement 335646 MOLBIL. This work is part of the research programme of the Netherlands Organization for Scientific Research (NWO). J.K. acknowledges financial support through US NSF grant no. CHE-1565872 to X.X. Xxxxxxxxx. The authors thank X. Xxxxxxxx, X. Xxxxxxx and X. xxx Xxxx for expert technical support, and
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Chem. Rev. 2007, 107, 4891–4932. In the first case, an additional fused benzene unit is obtained by the thermal cycloaromatization reaction of an 10.1021/ol201290q Ⓒ 2011 American Chemical Society Published on Web 06/07/2011 enediyne system (1); in the latter case, the benzene ring is formed upon the Xxxxx-acid-catalyzed oxidative coupling of two ortho-localized phenyl rings (2). The second method is of particular interest and to date, represents the most efficient tool to access PAHs, as well-defined cut-outs of graphene.1,2,8a — The major challenge that needs to be addressed when building up larger aromatic structures is to retain the efficiency of each step upon the increase of the core size; an issue associated with the restricted solubility of larger cores when solubilizing tails can only be introduced in the final stage of the synthesis. In the course of our studies on employing the triazole moiety as an aromaticity-extending building block,9 it was of interest to probe whether a bis(triazole) system similar to the bis(phenyl) system 2 could be employed to construct an additional fused benzene unit. The triazole ring can be obtained using the powerful Cu-catalyzed azide alkyne cycloaddition (CuAAC) reaction:10 a versatile alternative method. — Initially, three ortho-bis(triazole) systems 3, 4, and 5 were investigated as the precursors for the synthesis of the fused product 6. Compared with 3 5, aromaticity in 6 is extended by an additional benzene and two triazole rings, which, in principle, can be achieved by either the cyclode- hydrogenation (B) or homocoupling (C) reactions. The preliminary studies, performed on analogues of 3 by using method B, did not lead to the formation of the desired fused products. Thus, method C (4 and 5) was subse- quently investigated and optimized. The results are reported below. — Precursors 4 and 5 possess two 1,4,5-trisubstituted tria- zole rings, bearing a halogen atom (Br or I, respectively) in the 5-position, and were prepared using the Cu-catalyzed azide haloalkyne cycloaddition (CuAHAC) method.11 This method employs terminal acetylenes bearing a halo- gen atom insteadof a proton, and to date, several variations of this methodology are known in the literature.12,13 Among these, two methods employing a catalytic amount of the Cu(I) source are of special interest, and these were tested in the preparation of 4 and 5. The first procedure employs the CuAHAC reaction of bromoacetylenes with various azides, using a catalytic ...
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Chem. Int. Ed. 2017, 5G, 217 –220 T 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 217 attachment to a negatively charged oxygen atom has on nearby single bonds, when the charge is not partially compensated by a counterion. Recently these laboratories reported density functional (DFT) calculations that predict a red shift of hundreds of wavenumbers for the a-CH stretching frequencies of free alkoxide ions relative to their alkali metal salts.[6] Here we present experimental confirmation of those predictions using inter alia the free electron laser for infrared experiments (XXXXX). Some of these CH stretches occur even lower than 5 the lowest CH stretch of protonated methane (CH +).[1] Figure 1 and Table 1 summarize the experimental results and Figure 2 compares a pair of results with theory. Because the spectra were recorded at room temperature, hot bands (excitations arising from states above the lowest level) are sometimes seen as shoulders to the red of the principal peak, but are not tabulated below. Combination bands and over- tones are also not tabulated.
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Chem. Phys. 1997, 106, 7541-7549. c) Xxxxxxxxxx, X.; Xxxxx, D. M.; Xxxxxx, X.; Xxxxx, X. X. Am. Chem. Soc. 1997, 119, 8083-8088. d) Xxxxxx, X. X.; Xxxxx, X.; Xxxxxxx, X.; Xxxx, X. Theor. Chem. Acc. 1998, 99, 95-99. e) Xxxxx, K.K.; Xxxxx, X.; Xxxxxxx, G. K. S.; Xxxx, G. A. J. Org. Chem. 2002, 67, 2913-2918. 20 Xxxxxxxxx, X.; Xxxxx, X.; Xxxxxxx, X.; Xxxxxxxx, X.; Xxxxxx, A. J. Org. Chem. 2001, 66, 6353-6363. 21 Xxxxx, X. X.; Xxxxx, X. March’s Advanced Organic Chemistry, Reactions, Mechanisms, and Structure, Xxxx Xxxxx & Sons, Inc., New York: 2001, Chapter 8, pp 338-342.
