The discovery of the novel reactivity of conjugated enynes,mediated by readily available halogenation reagents,opens a broad range of mechanistically unique pathways for the synthesis of highly functionalized chiral a...The discovery of the novel reactivity of conjugated enynes,mediated by readily available halogenation reagents,opens a broad range of mechanistically unique pathways for the synthesis of highly functionalized chiral allene derivatives.Bromoallenyl pyrrolidines can be synthesized via 1,4-addition of sulfonamide nitrogen nucleophiles and halogens to conjugated enynes.This process can lead to simultaneous formation of a highly functionalized axially chiral allene and a stereogenic center under economical and environmentally friendly reaction conditions.展开更多
This paper presents a series of first- and second-generation click-modified coumarin-based fluorescent probes for thiols. These molecules demonstrate high turn-on fluorescent response and good selectivity towards arom...This paper presents a series of first- and second-generation click-modified coumarin-based fluorescent probes for thiols. These molecules demonstrate high turn-on fluorescent response and good selectivity towards aromatic thiols over other relevant reac- tive sulfur species, reactive oxygen species and common nucleophiles. Moreover, probe la can detect thiols in the reduced rabbit plasma sample. Therefore, this approach provides a particularly impressive tool for detecting thiol in biological systems.展开更多
Coupling reaction usually refers to the direct C–C bond formation between two carbon fragments.Generally, cross-coupling reactions between nucleophiles and electrophiles have been extensively studied and become the c...Coupling reaction usually refers to the direct C–C bond formation between two carbon fragments.Generally, cross-coupling reactions between nucleophiles and electrophiles have been extensively studied and become the classic model for bond constructions. Another reaction model, bond formation from two nucleophiles through oxidative cross-coupling, has received more and more attention over the past few years. This paper will discuss the concept of oxidative cross-coupling and give an overview of its recent development.展开更多
The mechanisms of gold（I）-catalyzed cycloaddition of 1-（1-alkynyl） cyclopropyl ketones with nucleophiles have been investi- gated using density functional theory calculations at the B3LYP/6-31G （d, p） level of t...The mechanisms of gold（I）-catalyzed cycloaddition of 1-（1-alkynyl） cyclopropyl ketones with nucleophiles have been investi- gated using density functional theory calculations at the B3LYP/6-31G （d, p） level of theory. A polarizable continuum model （PCM） has been established in order to evaluate the effects of solvents on the reactions. The results of the calculations indicate that the first step of the catalytic cycle is the cyclization of the carbonyl oxygen onto the triple bond which forms a new and stable resonance structure of an oxonium ion and a carbocation intermediate. The subsequent ring expansion step results in the formation of the final product and regeneration of the catalyst. Furthermore, the regioselectivity and effect of substituents has been discussed, including an analysis of energy, bond length, and natural bond orbital （NBO） charge distributions in the rate-determining step. Our computational results are consistent with earlier experimental observations.展开更多
Single-atom catalysts(SACs) with well-defined and specific single-atom dispersion on supports offer great potential for achieving both high catalytic activity and selectivity. Covalent organic frameworks(COFs) with ta...Single-atom catalysts(SACs) with well-defined and specific single-atom dispersion on supports offer great potential for achieving both high catalytic activity and selectivity. Covalent organic frameworks(COFs) with tailormade crystalline structures and designable atomic composition is a class of promising supports for SACs. Herein, we have studied the binding sites and stability of Pd single atoms(SAs)dispersed on triazine COF(Pd1/trzn-COF) and the reaction mechanism of CO oxidation using the density functional theory(DFT). By evaluating different adsorption sites, including the nucleophilic sp2C atoms, heteroatoms and the conjugated π-electrons of aromatic ring and triazine, it is found that Pd SAs can stably combine with trzn-COF with a binding energy around-5.0 eV, and there are two co-existing dynamic Pd1/trzn-COFs due to the adjacent binding sites on trzn-COF. The reaction activities of CO oxidation on Pd1/trzn-COF can be regulated by the anion–π interaction between a +δ phenyl center and the related-δ moieties as well as the electron-withdrawing feature of imine in the specific complexes. The Pd1/trzn-COF catalyst is found to have a high catalytic activity for CO oxidation via a plausible tri-molecular Eley-Rideal(TER) reaction mechanism. This work provides insights into the d–π interaction between Pd SAs and trznCOF, and helps to better understand and design new SACs supported on COF nanomaterials.展开更多
基金the University of Wisconsin-Madison and the American Chemical Society Petroleum Research Fund (48092-G) for funding
文摘The discovery of the novel reactivity of conjugated enynes,mediated by readily available halogenation reagents,opens a broad range of mechanistically unique pathways for the synthesis of highly functionalized chiral allene derivatives.Bromoallenyl pyrrolidines can be synthesized via 1,4-addition of sulfonamide nitrogen nucleophiles and halogens to conjugated enynes.This process can lead to simultaneous formation of a highly functionalized axially chiral allene and a stereogenic center under economical and environmentally friendly reaction conditions.
基金financed by grants from Shandong Natural Science Foundation (JQ201019)Independent Innovation Foundation of Shandong University,IIFSDU (2010JQ005)
文摘This paper presents a series of first- and second-generation click-modified coumarin-based fluorescent probes for thiols. These molecules demonstrate high turn-on fluorescent response and good selectivity towards aromatic thiols over other relevant reac- tive sulfur species, reactive oxygen species and common nucleophiles. Moreover, probe la can detect thiols in the reduced rabbit plasma sample. Therefore, this approach provides a particularly impressive tool for detecting thiol in biological systems.
基金supported by the National Basic Research Program of China(2012CB725302)the National Natural Science Foundation of China(21390400,21272180,21302148)+1 种基金the Research Fund for the Doctoral Program of Higher Education of China(20120141130002)the Ministry of Science and Technology of China(2012YQ120060)
文摘Coupling reaction usually refers to the direct C–C bond formation between two carbon fragments.Generally, cross-coupling reactions between nucleophiles and electrophiles have been extensively studied and become the classic model for bond constructions. Another reaction model, bond formation from two nucleophiles through oxidative cross-coupling, has received more and more attention over the past few years. This paper will discuss the concept of oxidative cross-coupling and give an overview of its recent development.
基金supported by the Natural Science Foundation of Gansu Province (10710RJZA114)
文摘The mechanisms of gold（I）-catalyzed cycloaddition of 1-（1-alkynyl） cyclopropyl ketones with nucleophiles have been investi- gated using density functional theory calculations at the B3LYP/6-31G （d, p） level of theory. A polarizable continuum model （PCM） has been established in order to evaluate the effects of solvents on the reactions. The results of the calculations indicate that the first step of the catalytic cycle is the cyclization of the carbonyl oxygen onto the triple bond which forms a new and stable resonance structure of an oxonium ion and a carbocation intermediate. The subsequent ring expansion step results in the formation of the final product and regeneration of the catalyst. Furthermore, the regioselectivity and effect of substituents has been discussed, including an analysis of energy, bond length, and natural bond orbital （NBO） charge distributions in the rate-determining step. Our computational results are consistent with earlier experimental observations.
基金supported by the National Natural Science Foundation of China (22033005,21590792 and 21763006)Guangdong Provincial Key Laboratory of Catalysis (2020B121201002)。
文摘Single-atom catalysts(SACs) with well-defined and specific single-atom dispersion on supports offer great potential for achieving both high catalytic activity and selectivity. Covalent organic frameworks(COFs) with tailormade crystalline structures and designable atomic composition is a class of promising supports for SACs. Herein, we have studied the binding sites and stability of Pd single atoms(SAs)dispersed on triazine COF(Pd1/trzn-COF) and the reaction mechanism of CO oxidation using the density functional theory(DFT). By evaluating different adsorption sites, including the nucleophilic sp2C atoms, heteroatoms and the conjugated π-electrons of aromatic ring and triazine, it is found that Pd SAs can stably combine with trzn-COF with a binding energy around-5.0 eV, and there are two co-existing dynamic Pd1/trzn-COFs due to the adjacent binding sites on trzn-COF. The reaction activities of CO oxidation on Pd1/trzn-COF can be regulated by the anion–π interaction between a +δ phenyl center and the related-δ moieties as well as the electron-withdrawing feature of imine in the specific complexes. The Pd1/trzn-COF catalyst is found to have a high catalytic activity for CO oxidation via a plausible tri-molecular Eley-Rideal(TER) reaction mechanism. This work provides insights into the d–π interaction between Pd SAs and trznCOF, and helps to better understand and design new SACs supported on COF nanomaterials.
