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961.
A scheme for calculating nuclear magnetic shieldings using the infinite-order Foldy–Wouthuysen (FW) transformation proposed by Barysz and Sadlej (BS) is presented. The nuclear magnetic shieldings of hydrogen halides are calculated by three variant BS schemes; a double finite perturbation method for the external magnetic flux density (B 0) and the nuclear magnetic dipole moment (? μ M ) (BS/FPT-2), a single finite perturbation method for B 0 with analytical differentiation of energy with respect to (? μ M ) (BS/FPT-1), and an approximate analytical differentiation method with respect to both B 0 and μ M (BS/CHF). Although the BS/FPT-2 method is exact theoretically, the actual computation for heavy nuclei includes large error due to reduction of the number of significant figures. The BS/FPT-1 and BS/CHF approaches, on the other hand, yield reasonable values for all of the shieldings. Although several results could not be obtained by the BS/FPT-2 method, no serious contradictions were recognized among these three results. From a comparison of our results with values in the literature, our shieldings for the halogen nuclei are lower than those determined by the four-component relativistic random phase approximation (4-RPA), but the reason for this is not obvious. 相似文献
962.
Semigroup Forum - A binary operation f(x, y) is said to be lazy if every operation that can be obtained from f by composition is equivalent to f(x, y), f(x, x) or x. We... 相似文献
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964.
Daiki Tanaka Yuya Tsutsui Dr. Akihito Konishi Koichi Nakaoka Dr. Hideto Nakajima Prof. Dr. Akio Baba Dr. Kouji Chiba Prof. Dr. Makoto Yasuda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(65):15023-15034
Selective bond formations are one of the most important reactions in organic synthesis. In the Lewis acid mediated electrophile reactions of carbonyls, the selective formation of a carbonyl–acid complex plays a critical role in determining selectivity, which is based on the difference in the coordinative interaction between the carbonyl and Lewis acid center. Although this strategy has attained progress in selective bond formations, the discrimination between similarly sized aromatic and aliphatic carbonyls that have no functional anchors to strongly interact with the metal center still remains a challenging issue. Herein, this work focuses on molecular recognition driven by dispersion interactions within some aromatic moieties. A Lewis acid catalyst with a π-space cavity, which is referred to as a π-pocket, as the recognition site for aromatic carbonyls is designed. Cage-shaped borates 1 B with various π-pockets demonstrated significant chemoselectivity for aromatic aldehydes 3 b – f over that of aliphatic 3 a in competitive hetero-Diels–Alder reactions. The effectiveness of our catalysts was also evidenced by intramolecular recognition of the aromatic carbonyl within a dicarbonyl substrate. Mechanistic and theoretical studies demonstrated that the selective activation of aromatic substrates was driven by the preorganization step with a larger dispersion interaction, rather than the rate-determining step of the C−C bond formation, and this was likely to contribute to the preferred activation of aromatic substrates over that of aliphatic ones. 相似文献
965.
Dr. Yadong Pang Joo Won Lee Prof. Dr. Koji Kubota Prof. Dr. Hajime Ito 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(50):22759-22765
The application of piezoelectricity for the generation of trifluoromethyl (CF3) radicals is reported together with the development of a method for the mechanochemical C−H trifluoromethylation of aromatic compounds. As compared to conventional solution-based approaches, this mechanoredox C−H trifluoromethylation enables cleaner and more sustainable access to a wide range of trifluoromethylated N-heterocycles and peptides, which are important structural motifs in modern drug discovery. This study thus represents an important milestone for future applications of mechanoredox systems to medicinal and pharmaceutical science. 相似文献
966.
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968.
969.
Chunlin Wu Xurong Qin Adhitya Mangala Putra Moeljadi Hajime Hirao Jianrong Steve Zhou 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(9):2731-2735
Copper complexes of monodentate phosphoramidites efficiently promote asymmetric arylation of N‐azaaryl aldimines with arylboroxines. DFT calculations and experiments support an elementary step of 1,4‐insertion in the reaction pathway, a step in which an aryl‐copper species adds directly across four atoms of C=N?C=N in the N‐azaaryl aldimines. 相似文献