Crystal structure and crystallinity of carbon nitride support, size and dispersity of active-metal nanoparticles(NPs), and surface engineering of composites have great roles in generation and separation of photogenera...Crystal structure and crystallinity of carbon nitride support, size and dispersity of active-metal nanoparticles(NPs), and surface engineering of composites have great roles in generation and separation of photogenerated charge carries and photocatalyzed organic reactions for the conversion of solar energy into chemical energy. Herein, we deposited well-dispersed Pd NPs with small size on crystallized carbon nitride(CN–C) to construct a Schottky-type Pd/CN–C hybrid for photocatalyzed Ullmann C–C homocoupling of aryl halides under visible light irradiation at room temperature. Compared to Pd NPs supported g-C_3N_4(Pd/g-C_3N_4), Pd/CN–C exhibits excellent visible light photocatalytic activity for Ullmann C–C coupling of aryl halides due to high crystallinity of CN–C support, high dispersion and smaller size of Pd NPs, and the interfacial heterojunction of Pd/CN–C. Upon visible light irradiation, more photogenerated electrons from CN–C flow across the Schottky junction to metallic Pd and trigger the Ullmann C–C coupling of aryl halides. The photogenerated holes on CN–C surface are captured by a protic solvent(such as EtOH). In the presence of base K_2CO_3, the solvent undergoes dissociation, dehydrogenation, and finally can be oxidized by captured photogenerated holes. Moreover, Pd/CN–C has general applicability for various substrates and shows excellent stability and reusability for more than nine cycles.展开更多
A general, rapid and highly efficient method for the synthesis of diaryl ethers under the assistance of microwave irradiation was described. A series of diaryl ethers were prepared by direct coupling of phenols and ar...A general, rapid and highly efficient method for the synthesis of diaryl ethers under the assistance of microwave irradiation was described. A series of diaryl ethers were prepared by direct coupling of phenols and aryl halides in good to excellent yields in anhydrous DMF or NMP at 150 ℃ within 20 rain. The presence of water was found to have a significant impact on the Ullmann C-O coupling reaction between aryl halides and phenols under microwave irradiation.展开更多
In water, ammonium chloride was found to promote palladium-catalyzed Ullmann coupling reactions of aryl bromides. In the presence of Pd/C, zinc, NH4Cl, and water, coupling of various aryl bromides was carried out smoo...In water, ammonium chloride was found to promote palladium-catalyzed Ullmann coupling reactions of aryl bromides. In the presence of Pd/C, zinc, NH4Cl, and water, coupling of various aryl bromides was carried out smoothly to afford the corresponding homocoupling products in moderate yields.展开更多
Novel magnetic core/shell bimetallic Au/Cu nanoparticles（Fe_3O_4@SiO_2-Au/Cu NPs） were prepared using SiO_2-coated iron oxide（Fe_3O_4@SiO_2） as a supported material. The magnetic Fe_3O_4 colloidal nanocrystal clus...Novel magnetic core/shell bimetallic Au/Cu nanoparticles（Fe_3O_4@SiO_2-Au/Cu NPs） were prepared using SiO_2-coated iron oxide（Fe_3O_4@SiO_2） as a supported material. The magnetic Fe_3O_4 colloidal nanocrystal clusters（CNCs） as nano-core were modified with a silica coating for improvement stability and superficial area of the Au-Cu particles. The morphological structure and chemical composition of the Fe_3O_4@SiO_2-Au/Cu NPs were characterized with high-resolution transmission electron microscopy（HRTEM）, energy-dispersive X-ray（EDX） and X-ray photoelectron spectroscopy（XPS） analyses. The Au and Cu NPs were deposited on the SiO_2 surface in a highly dense and well dispersed manner with an average size of approximately 5 nm. The Fe_3O_4@SiO_2-Au/Cu NPs as magnetic nano-catalysts were applied to the Ullmann coupling reaction of bromamine acid to synthesize 4,40-diamino-1,10-dianthraquinonyl-3,30-disulfonic acid（DAS）. The prepared Fe_3O_4@SiO_2-Au/Cu NPs exhibited efficient catalytic activity with higher conversion and selectivity. A bromamine acid conversion of 97.35% and selectivity for DAS of 88.67% were obtained in aqueous medium. The magnetic nano-catalysts can be readily separated from the reaction system and reused. This new nano-catalytic reaction represents a useful and attractive cleaner production system. The new catalyst system has important and potential applications in dye and pigment industry.展开更多
The carbon–carbon couplings of 4,4＇＇-dibromo-p-terphenyl（DBTP） on Cu（110） surface have been investigated at a single molecular level by scanning tunneling microscopy. After annealing at 353 K, a mixture of para...The carbon–carbon couplings of 4,4＇＇-dibromo-p-terphenyl（DBTP） on Cu（110） surface have been investigated at a single molecular level by scanning tunneling microscopy. After annealing at 353 K, a mixture of parallel non-organometallic and organometallic intermediates of DBTP molecules along the[1–10] direction of the surface has been observed. Further annealing at 393 K causes one group of molecules to form oligomers with para-para and para-meta motifs via Ullmann reaction and the other group of molecules to synthesize oligomers with meta-meta motifs via direct carbon–carbon coupling reaction. Statistical results directly reveal that the occurrence of reaction type is strongly related to the initial binding configuration of DBTP molecules.展开更多
By optimizing the reaction conditions via a careful screening of the bases and solvents, we developed an efficient transition metal-free method for C--O cross-coupling of activated and unactivated heteroaryl chlorides...By optimizing the reaction conditions via a careful screening of the bases and solvents, we developed an efficient transition metal-free method for C--O cross-coupling of activated and unactivated heteroaryl chlorides with primary and secondary alcohols and phenols, providing a simple, efficient, and practical method for synthesis of the useful unsymmetrical heteroaryl alkyl and heteroaryl aryl ethers.展开更多
对Ru59063的合成进行了改进。首先,4-氨基-2-(三氟甲基)苯甲腈(Ⅲ)与硫光气反应,制备了4-异硫氰基-2-(三氟甲基)苯腈(Ⅳ);然后,中间体Ⅳ与2-氨基异丁酸甲酯盐酸盐进行[3+2]环加成反应,合成了4-(2-硫代-4,4-二甲基-5-氧代咪唑烷-1-基)-2...对Ru59063的合成进行了改进。首先,4-氨基-2-(三氟甲基)苯甲腈(Ⅲ)与硫光气反应,制备了4-异硫氰基-2-(三氟甲基)苯腈(Ⅳ);然后,中间体Ⅳ与2-氨基异丁酸甲酯盐酸盐进行[3+2]环加成反应,合成了4-(2-硫代-4,4-二甲基-5-氧代咪唑烷-1-基)-2-三氟甲基苯腈(Ⅶ);化合物Ⅶ再与叔丁基-(4-氯丁氧基)-二甲基硅烷通过乌尔曼C—N偶联反应,得到了4-{3-[4-(叔丁基二甲基硅基)-羟基丁基]-4,4-二甲基-5-氧代-2-硫代咪唑烷-1-基}-2-(三氟甲基)苯甲腈(Ⅷ);最后,中间体Ⅷ进行羟基脱保护得到Ru59063,4步反应总收率为61.6%,HPLC纯度为98.2%。与传统方法相比,该法收率提高了4.7倍,并且未使用氰化物,可以更方便、更安全地制备了Ru59063。对2 kg 4-氨基-2-(三氟甲基)苯甲腈进行了放大实验,总收率可达到60.7%。展开更多
From a molecular level to an ecosystem scale,different coupling mechanisms take place during coupled carbonnitrogen-water(C-N-H2O)cycle,of which essential are water flux and related biogeochemical processes through ph...From a molecular level to an ecosystem scale,different coupling mechanisms take place during coupled carbonnitrogen-water(C-N-H2O)cycle,of which essential are water flux and related biogeochemical processes through physicochemical reactions associated with terrestrial and aquatic ecosystems.Meanwhile,regional coupled C-N-H2O cycle will subsequently impact regional gross primary productivity(GPP)and C and N exchanges during air-water interactions that occur downstream of watersheds.This study aimed to first synthetically analyze the regional dynamics of C,N and H2O cycles in ecosystems and determine their interactional relationships;second,to specify regional C-N-H2O coupled relationships of ecosystems and their theoretical ecological principles;third,to classify coupled regional response and adaptation of the C-N-H2O cycle to climatic and environmental changes under anthropogenic activities,providing a theoretical basis to fully understand and make adjustments to interactional C,N and H2O cycling relationships at different ecosystem scales and under associated coupling processes.展开更多
基金financially supported by the National Natural Science Foundation of China(No.21503127)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2017JM2008)the 111 Project(B14041)
文摘Crystal structure and crystallinity of carbon nitride support, size and dispersity of active-metal nanoparticles(NPs), and surface engineering of composites have great roles in generation and separation of photogenerated charge carries and photocatalyzed organic reactions for the conversion of solar energy into chemical energy. Herein, we deposited well-dispersed Pd NPs with small size on crystallized carbon nitride(CN–C) to construct a Schottky-type Pd/CN–C hybrid for photocatalyzed Ullmann C–C homocoupling of aryl halides under visible light irradiation at room temperature. Compared to Pd NPs supported g-C_3N_4(Pd/g-C_3N_4), Pd/CN–C exhibits excellent visible light photocatalytic activity for Ullmann C–C coupling of aryl halides due to high crystallinity of CN–C support, high dispersion and smaller size of Pd NPs, and the interfacial heterojunction of Pd/CN–C. Upon visible light irradiation, more photogenerated electrons from CN–C flow across the Schottky junction to metallic Pd and trigger the Ullmann C–C coupling of aryl halides. The photogenerated holes on CN–C surface are captured by a protic solvent(such as EtOH). In the presence of base K_2CO_3, the solvent undergoes dissociation, dehydrogenation, and finally can be oxidized by captured photogenerated holes. Moreover, Pd/CN–C has general applicability for various substrates and shows excellent stability and reusability for more than nine cycles.
基金Project supported by the Guangdong Provincial Natural Science Foundation （No. 04009718）
文摘A general, rapid and highly efficient method for the synthesis of diaryl ethers under the assistance of microwave irradiation was described. A series of diaryl ethers were prepared by direct coupling of phenols and aryl halides in good to excellent yields in anhydrous DMF or NMP at 150 ℃ within 20 rain. The presence of water was found to have a significant impact on the Ullmann C-O coupling reaction between aryl halides and phenols under microwave irradiation.
基金Project supported by the National Natural Science Foundation of China (No. 20202002) Hunan Province Department of Education (No. 02C211) and Hunan Normal University (2001).
文摘In water, ammonium chloride was found to promote palladium-catalyzed Ullmann coupling reactions of aryl bromides. In the presence of Pd/C, zinc, NH4Cl, and water, coupling of various aryl bromides was carried out smoothly to afford the corresponding homocoupling products in moderate yields.
基金financially supported by the Shanghai Natural Science Foundation (No. 13ZR1400300)National Key R&D Program of China (No. 2017YFB030900)
文摘Novel magnetic core/shell bimetallic Au/Cu nanoparticles（Fe_3O_4@SiO_2-Au/Cu NPs） were prepared using SiO_2-coated iron oxide（Fe_3O_4@SiO_2） as a supported material. The magnetic Fe_3O_4 colloidal nanocrystal clusters（CNCs） as nano-core were modified with a silica coating for improvement stability and superficial area of the Au-Cu particles. The morphological structure and chemical composition of the Fe_3O_4@SiO_2-Au/Cu NPs were characterized with high-resolution transmission electron microscopy（HRTEM）, energy-dispersive X-ray（EDX） and X-ray photoelectron spectroscopy（XPS） analyses. The Au and Cu NPs were deposited on the SiO_2 surface in a highly dense and well dispersed manner with an average size of approximately 5 nm. The Fe_3O_4@SiO_2-Au/Cu NPs as magnetic nano-catalysts were applied to the Ullmann coupling reaction of bromamine acid to synthesize 4,40-diamino-1,10-dianthraquinonyl-3,30-disulfonic acid（DAS）. The prepared Fe_3O_4@SiO_2-Au/Cu NPs exhibited efficient catalytic activity with higher conversion and selectivity. A bromamine acid conversion of 97.35% and selectivity for DAS of 88.67% were obtained in aqueous medium. The magnetic nano-catalysts can be readily separated from the reaction system and reused. This new nano-catalytic reaction represents a useful and attractive cleaner production system. The new catalyst system has important and potential applications in dye and pigment industry.
基金financially supported by Natural Science Foundation of China (Nos. 61474059, U1432129 and 11504158)National Key Basic Research Program of China (No. 2013CB934200)
文摘The carbon–carbon couplings of 4,4＇＇-dibromo-p-terphenyl（DBTP） on Cu（110） surface have been investigated at a single molecular level by scanning tunneling microscopy. After annealing at 353 K, a mixture of parallel non-organometallic and organometallic intermediates of DBTP molecules along the[1–10] direction of the surface has been observed. Further annealing at 393 K causes one group of molecules to form oligomers with para-para and para-meta motifs via Ullmann reaction and the other group of molecules to synthesize oligomers with meta-meta motifs via direct carbon–carbon coupling reaction. Statistical results directly reveal that the occurrence of reaction type is strongly related to the initial binding configuration of DBTP molecules.
文摘By optimizing the reaction conditions via a careful screening of the bases and solvents, we developed an efficient transition metal-free method for C--O cross-coupling of activated and unactivated heteroaryl chlorides with primary and secondary alcohols and phenols, providing a simple, efficient, and practical method for synthesis of the useful unsymmetrical heteroaryl alkyl and heteroaryl aryl ethers.
文摘对Ru59063的合成进行了改进。首先,4-氨基-2-(三氟甲基)苯甲腈(Ⅲ)与硫光气反应,制备了4-异硫氰基-2-(三氟甲基)苯腈(Ⅳ);然后,中间体Ⅳ与2-氨基异丁酸甲酯盐酸盐进行[3+2]环加成反应,合成了4-(2-硫代-4,4-二甲基-5-氧代咪唑烷-1-基)-2-三氟甲基苯腈(Ⅶ);化合物Ⅶ再与叔丁基-(4-氯丁氧基)-二甲基硅烷通过乌尔曼C—N偶联反应,得到了4-{3-[4-(叔丁基二甲基硅基)-羟基丁基]-4,4-二甲基-5-氧代-2-硫代咪唑烷-1-基}-2-(三氟甲基)苯甲腈(Ⅷ);最后,中间体Ⅷ进行羟基脱保护得到Ru59063,4步反应总收率为61.6%,HPLC纯度为98.2%。与传统方法相比,该法收率提高了4.7倍,并且未使用氰化物,可以更方便、更安全地制备了Ru59063。对2 kg 4-氨基-2-(三氟甲基)苯甲腈进行了放大实验,总收率可达到60.7%。
基金supported by the National Science Fund for Excellent Young Scholars(Grant No.41922003)National Natural Science Foundation of China(Grant No.41871080)。
文摘From a molecular level to an ecosystem scale,different coupling mechanisms take place during coupled carbonnitrogen-water(C-N-H2O)cycle,of which essential are water flux and related biogeochemical processes through physicochemical reactions associated with terrestrial and aquatic ecosystems.Meanwhile,regional coupled C-N-H2O cycle will subsequently impact regional gross primary productivity(GPP)and C and N exchanges during air-water interactions that occur downstream of watersheds.This study aimed to first synthetically analyze the regional dynamics of C,N and H2O cycles in ecosystems and determine their interactional relationships;second,to specify regional C-N-H2O coupled relationships of ecosystems and their theoretical ecological principles;third,to classify coupled regional response and adaptation of the C-N-H2O cycle to climatic and environmental changes under anthropogenic activities,providing a theoretical basis to fully understand and make adjustments to interactional C,N and H2O cycling relationships at different ecosystem scales and under associated coupling processes.
