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101.
Dr. Hua Wu Dr. Qian Wang Prof. Dr. Jieping Zhu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(21):5952-5955
We report an unprecedented organocatalytic enantioselective acyloin rearrangement of α,α-disubstituted α-hydroxy acetals. In the presence of a catalytic amount of chiral binol-derived N-triflyl phosphoramide, α-hydroxy acetals rearranged to α-alkoxy ketones in good to high yields with high enantioselectivities. Formation of an ion pair between the in situ generated oxocarbenium ion and the chiral phosphoramide anion was proposed to be responsible for the highly efficient transfer of chirality. Conditions for removal of cyclohexyl and cyclopentyl groups from the corresponding α-alkoxy ketones were uncovered underpinning their potential general utility as hydroxy protecting groups. Conversion of the rearranged products to the enantioenriched α-hydroxy ketone, 1,2-diol, β-amino alcohol and 1,4-dioxane was also documented. 相似文献
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Yadong Yu Zhao Mu Dr. Biao Jin Dr. Zhaoming Liu Prof. Ruikang Tang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(5):2087-2091
Ionic oligomers and their crosslinking implies a possibility to produce novel organic–inorganic composites by copolymerization. Using organic acrylamide monomers and inorganic calcium phosphate oligomers as precursors, uniformly structured polyacrylamide (PAM)-calcium phosphate copolymer is prepared by an organic–inorganic copolymerization. In contrast to the previous PAM-based composites by mixing inorganic components into polymers, the copolymerized material has no interphase boundary owing to the homogenous incorporation of the organic and inorganic units at molecular level, resulting in a complete and continuous hybrid network. The participation of the ionic binding effect in the crosslinking process can substantially improve the mechanical strength; the copolymer can reach a modulus and hardness of 35.14±1.91 GPa and 1.34±0.09 GPa, respectively, which are far superior to any other PAM-based composites. 相似文献
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Dr. Yijing Chen Weinan Chen Dr. Yanjun Qiao Prof. Dr. Xuefeng Lu Prof. Dr. Gang Zhou 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(18):7188-7196
BN-embedded oligomers with different pairs of BN units were synthesized by electrophilic borylation. Up to four pairs of BN units were incorporated in the large polycyclic aromatic hydrocarbons (PAHs). Their geometric, photophysical, electrochemical, and Lewis acidic properties were investigated by X-ray crystallography, optical spectroscopy, and cyclic voltammetry. The B−N bonds show delocalized double-bond characteristics and the conjugation can be extended through the trans-orientated aromatic azaborine units. Calculations reveal the relatively lower aromaticity for the inner azaborine rings in the BN-embedded PAH oligomers. The frontier orbitals of the longer oligomers are delocalized over the inner aromatic rings. Consequently, the inner moieties of the BN-embedded PAH oligomers are more active than the outer parts. This is confirmed by a simple oxidation reaction, which has significant effects on the aromaticity and the intramolecular charge-transfer interactions. 相似文献
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Yuan Cai Xiaodong Ye Sheng Liu Shi‐Liang Shi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(38):13567-13571
Chiral polyfluoroarene derivatives are an important scaffold in chemistry. An unprecedented enantioselective C?H alkylation of polyfluoroarenes with alkenes is described. The reaction employs bulky chiral N‐heterocyclic carbene (NHC) ligands for nickel catalysts to enable exclusive activation of C?H bonds over C?F bonds and complete endo‐selective C?H annulation and excellent enantioselectivity. A wide variety of chiral fluorotetralins, compounds otherwise difficultly accessed but serve as important bioisosteric analogs of both tetralin and heterocycle units for drug design, are expediently synthesized from easily available substrates. To our knowledge, this is the first example of catalytic enantioselective C?H functionalization of polyfluoroarenes. 相似文献
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Hua‐Jie Jiang Xiu‐Mei Zhong Jie Yu Ying Zhang Xinhao Zhang Yun‐Dong Wu Liu‐Zhu Gong 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(6):1817-1821
An unusual hybrid palladium catalyst containing an anionic chiral CoIII complex and a chiral phosphoramidite ligand shows a high capacity for catalyzing asymmetric thioamide‐directed C(sp3)?H arylation and delivers excellent yield and enantioselectivity (up to 99 % yield, 99 % ee). Significant synergy between the chiral ligand and the anion in terms of stereochemical control was observed. Mechanistic investigations have revealed both the nature of the C?H activation and the origin of the enantioselectivity. 相似文献
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Suneesh C. Karunakaran Brian J. Cafferty Angela Weigert‐Muoz Gary B. Schuster Nicholas V. Hud 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(5):1467-1471
Aqueous solutions of the achiral, monomeric, nucleobase mimics (2,4,6‐triaminopyrimidine, TAP, and a cyanuric acid derivative, CyCo6) spontaneously assemble into macroscopic homochiral domains of supramolecular polymers. These assemblies exhibit a high degree of chiral amplification. Addition of a small quantity of one handedness of a chiral derivative of CyCo6 generates exclusively homochiral structures. This system exhibits the highest reported degree of chiral amplification for dynamic helical polymers or supramolecular helices. Significantly, homochiral polymers comprised of hexameric rosettes with structural features that resemble nucleic acids are formed from mixtures of cyanuric acid (Cy) and ribonucleotides (l‐, d ‐pTARC) that arise spontaneously from the reaction of TAP with the sugars. These findings support the hypothesis that nucleic acid homochirality was a result of symmetry breaking at the supramolecular polymer level. 相似文献