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351.
Silica sulfuric acid (SSA) was found to efficiently catalyze the conversion of aldehydes and ketones directly into the corresponding gem-dihydroperoxides (DHPs) on treatment with aqueous 30% H2O2 at room temperature. Mild reaction conditions, good to excellent yields, short reaction times, low environmental impact, and recyclability of the catalyst are the main advantages of this synthetic method. 相似文献
352.
Javad Azizian Khadijeh Yadollahzadeh Hasan Tahermansouri Davood Chobfrosh Khoei Akram Sadat Delbari 《合成通讯》2013,43(14):2110-2120
Urea polyfunctional derivatives were successfully synthesized via a one-pot, five-component nucleophilic addition/Ugi reaction sequence. Simplicity, solvent-free conditions, and good yields of products are advantages of this method. 相似文献
353.
The conformational behavior of 1,2-difluoroethane (1), 1,2-dichloroethane (2), 1,2-dibromoethane (3), and 1,2-diiodoethane (4) have been analyzed by means of complete basis set CBS-QB3, hybrid-density functional theory (B3LYP/Def2-TZVPP) based methods
and natural bond orbital (NBO) interpretation. Both methods showed the expected greater stability of the gauche conformation
of compound 1 compared to its anti conformation. Contrary to compound 1, the anti conformations of compounds 2–4 are more stable than their gauche conformation. The stability of the anti conformation compared to the gauche conformation
increases from compound 1 to compound 4. The NBO analysis of donor–acceptor (σ → σ*) interactions showed that the generalized anomeric effect (GAE) is in favor of
the gauche conformation of compound 1. Contrary to compound 1, GAE is in favor of the anti conformations of compounds 2–4. The GAE values calculated (i.e., GAEanti − GAEgauche) increase from compound 1 to compound 4. On the other hand, the calculated dipole moment values for the gauche conformations decrease from compound 1 to compound 4. In the conflict between the GAE and dipole moments, the former succeeded in accounting for the increase of the anti conformation
stability from compound 1 to compound 4. There is a direct correlation between the calculated GAE, ∆[r
c–c(G) − r
c–c(A)] and ∆[r
c–x(A) − r
c–x(G)] parameters. The correlations between the GAE, bond orders, total steric exchange energies (TSEEs), ΔG
Anti–Gauche, ΔG
‡(Gauche → Gauche′, C
2v), ΔG
‡(Anti → Gauche, C
2), dipole–dipole interactions, structural parameters, and conformational behaviors of compounds 1–4 have been investigated. 相似文献
354.
The equilibrium three dimensional shape of relatively short loops of DNA is studied using an elastic model that takes into account anisotropy in bending rigidities. Using a reasonable estimate for the anisotropy, it is found that cyclized DNA with lengths that are not integer multiples of the pitch take on nontrivial shapes that involve bending out of planes and formation of kinks. The effect of sequence inhomogeneity on the shape of DNA is addressed, and shown to enhance the geometrical features. These findings could shed some light on the role of DNA conformation in protein-DNA interactions. 相似文献
355.
Dr. Yannan Liu Yiyue Lu Dr. Arafat Hossain Khan Dr. Gang Wang Yong Wang Dr. Ahiud Morag Dr. Zhiyong Wang Dr. Guangbo Chen Dr. Shengyun Huang Dr. Naisa Chandrasekhar Dr. Davood Sabaghi Dongqi Li Dr. Panpan Zhang Prof. Dongling Ma Prof. Eike Brunner Dr. Minghao Yu Prof. Xinliang Feng 《Angewandte Chemie (International ed. in English)》2023,62(30):e202306091
Emerging rechargeable aluminium batteries (RABs) offer a sustainable option for next-generation energy storage technologies with low cost and exemplary safety. However, the development of RABs is restricted by the limited availability of high-performance cathode materials. Herein, we report two polyimide two-dimensional covalent organic frameworks (2D-COFs) cathodes with redox-bipolar capability in RAB. The optimal 2D-COF electrode achieves a high specific capacity of 132 mAh g−1. Notably, the electrode presents long-term cycling stability (with a negligible ≈0.0007 % capacity decay per cycle), outperforming early reported organic RAB cathodes. 2D-COFs integrate n-type imide and p-type triazine active centres into the periodic porous polymer skeleton. With multiple characterizations, we elucidate the unique Faradaic reaction of the 2D-COF electrode, which involves AlCl2+ and AlCl4− dual-ions as charge carriers. This work paves the avenue toward novel organic cathodes in RABs. 相似文献