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991.
A Planar‐Chiral Rhodium(III) Catalyst with a Sterically Demanding Cyclopentadienyl Ligand and Its Application in the Enantioselective Synthesis of Dihydroisoquinolones 下载免费PDF全文
Dr. Evgeniya A. Trifonova Nikita M. Ankudinov Dr. Andrey A. Mikhaylov Dr. Denis A. Chusov Dr. Yulia V. Nelyubina Prof. Dr. Dmitry S. Perekalin 《Angewandte Chemie (International ed. in English)》2018,57(26):7714-7718
The rapid development of enantioselective C?H activation reactions has created a demand for new types of catalysts. Herein, we report the synthesis of a novel planar‐chiral rhodium catalyst [(C5H2tBu2CH2tBu)RhI2]2 in two steps from commercially available [(cod)RhCl]2 and tert‐butylacetylene. Pure enantiomers of the catalyst were obtained through separation of its diastereomeric adducts with natural (S)‐proline. The catalyst promoted enantioselective reactions of aryl hydroxamic acids with strained alkenes to give dihydroisoquinolones in high yields (up to 97 %) and with good stereoselectivity (up to 95 % ee). 相似文献
992.
Yanbo Mei Dong‐Jun Wu Dr. Jaap E. Borger Prof. Dr. Hansjörg Grützmacher 《Angewandte Chemie (International ed. in English)》2018,57(19):5512-5515
A simple synthesis of sodium 2‐phosphanaphthalene‐3‐olate ( 1 ) based on the extrusion of N2 from phthalazine using Na[OCP] is reported. This heterocycle can be readily functionalized at the negatively charged oxygen center using a variety of electrophilic substrates. The coordination chemistry of both 1 and its neutral derivatives was explored, revealing their facile use as P‐donor ligands for late‐transition‐metal complexes. 相似文献
993.
Zong‐Jie Guan Jiu‐Lian Zeng Shang‐Fu Yuan Feng Hu Dr. Yu‐Mei Lin Prof. Quan‐Ming Wang 《Angewandte Chemie (International ed. in English)》2018,57(20):5703-5707
The controlled synthesis and structure determination of a bimetallic nanocluster Au57Ag53(C≡CPh)40Br12 (Au57Ag53) is presented. The metal core has a four‐shell Au2M3@Au34@Ag51 @Au20 (M=1/3 Au+2/3 Ag) architecture. In contrast to the previously reported large nanoclusters that have highly symmetric kernel structures, the metal atoms in Au57Ag53 are arranged in an irregular manner with C1 symmetry. This cluster exhibits excellent thermal stability and is robust under oxidative or basic conditions. The silver precursors play a key role in dictating the structures of the nanoclusters, which suggests the importance of the counteranions used. 相似文献
994.
Andrew M. Poitras Sadie E. Knight Mark W. Bezpalko Bruce M. Foxman Christine M. Thomas 《Angewandte Chemie (International ed. in English)》2018,57(6):1497-1500
Addition of H2 across the cobalt–phosphorus bond of (PPP)CoPMe3 ( 3 ) is demonstrated, where PPP is a monoanionic diphosphine pincer ligand with a central N‐heterocyclic phosphido (NHP?) donor. The chlorophosphine CoII complex (PPClP)CoCl2 ( 2 ) can be generated through coordination of the chlorophosphine ligand (PPClP, 1 ) to CoCl2. Subsequent reduction of 2 with KC8 in the presence of PMe3 generates (PPP)CoPMe3 ( 3 ), in which both the phosphorus and cobalt centers have been reduced. The addition of 1 atm of H2 to complex 3 cleanly affords (PPHP)Co(H)PMe3 ( 4 ), in which H2 has ultimately been added across the metal–phosphorus bond. Complex 4 was characterized spectroscopically and using computational methods to predict its geometry. 相似文献
995.
Self‐Assembly of an Anion‐Binding Cryptand for the Selective Encapsulation,Sequestration, and Precipitation of Phosphate from Aqueous Systems 下载免费PDF全文
《Angewandte Chemie (International ed. in English)》2018,57(40):13071-13075
The self‐assembled trimetallic species [L2Cu3]6+ contains a cavity that acts as a host to many different anions. By using X‐ray crystallography, ESI‐MS, and UV/Vis spectroscopy we show that these anions are encapsulated both in the solid state and aqueous systems. Upon encapsulation, the anions Br−, I−, CO32−, SiF62−, IO63−, VO43−, WO42−, CrO42−, SO42−, AsO43−, and PO43− are all precipitated from aqueous solution and can be removed by filtration. Furthermore, the cavity can be tuned to be selective to either phosphate or sulfate anions by variation of the pH. Phosphate anions can be removed from water, even in the presence of other common anions, reducing the concentration from 1000 to <0.1 ppm and recovering approximately 99 % of the phosphate anions. 相似文献
996.
Chiral Bifunctional Phosphine‐Carboxylate Ligands for Palladium(0)‐Catalyzed Enantioselective C−H Arylation 下载免费PDF全文
Dr. Lei Yang Dr. Markus Neuburger Prof. Dr. Olivier Baudoin 《Angewandte Chemie (International ed. in English)》2018,57(5):1394-1398
Previous enantioselective Pd0‐catalyzed C?H activation reactions proceeding via the concerted metalation‐deprotonation mechanism employed either a chiral ancillary ligand, a chiral base, or a bimolecular mixture thereof. This study describes the development of new chiral bifunctional ligands based on a binaphthyl scaffold which incorporates both a phosphine and a carboxylic acid moiety. The optimal ligand provided high yields and enantioselectivities for a desymmetrizing C(sp2)?H arylation leading to 5,6‐dihydrophenanthridines, whereas the corresponding monofunctional ligands showed low enantioselectivities. The bifunctional system proved applicable to a range of substituted dihydrophenanthridines, and allowed the parallel kinetic resolution of racemic substrates. 相似文献
997.
Barbier–Negishi Coupling of Secondary Alkyl Bromides with Aryl and Alkenyl Triflates and Nonaflates 下载免费PDF全文
Ke‐Feng Zhang Fadri Christoffel Prof. Dr. Olivier Baudoin 《Angewandte Chemie (International ed. in English)》2018,57(7):1982-1986
A mild and practical Barbier–Negishi coupling of secondary alkyl bromides with aryl and alkenyl triflates and nonaflates has been developed. This challenging reaction was enabled by the use of a very bulky imidazole‐based phosphine ligand, which resulted in good yields as well as good chemo‐ and site selectivities for a broad range of substrates at room temperature and under non‐aqueous conditions. This reaction was extended to primary alkyl bromides by using an analogous pyrazole‐based ligand. 相似文献
998.
《Journal of separation science》2018,41(10):2110-2118
Two reversed‐phase/anion‐exchange mixed‐mode stationary phases for high‐performance liquid chromatography using calixtriazines as chromatographic ligands were investigated with Tanaka test solutes, monosubstituted benzenes, aromatic positional isomers, and inorganic anions. Calixtriazine as a chromatographic ligand has been reported previously, but the benzylated nitrogen‐bridged calixtriazine‐bonded silica gel reported in this study is new. The experimental data showed that the calixtriazine platform is a unique chromatographic selector because its multiple active sites are available for different solutes and its chromatographic selectivity could be tuned by introducing substituent on the bridging nitrogen atoms present in the calixtriazine matrix. The synergistic effects of aromatic rings, nitrogen atoms, benzyl groups, and tunable cavity in the host molecule influenced the separation selectivity by multiple retention mechanisms. Such hybrid stationary phases provide more versatility and have great potential in the analysis of complex samples. Moreover, the synthetic protocols presented herein may provide an alternative understanding on macrocyclic host–guest chemistry, leading to new and selective separation media. 相似文献
999.
William H. Watson Guanmin Wu Michael G. Richmond 《Journal of chemical crystallography》2004,34(10):709-716
The reaction of p-toluenethiol with 4,5-dichloro-4-cyclopenten-1,3-dione in 1,2-dichloroethane with added DBU affords good yields of the new bidentate sulfide ligand 4,5-bis(p-tolylthio)-4-cyclopenten-1,3-dione. The title compound was isolated by column chromatography and characterized in solution by IR and NMR spectroscopies. The solid-state structure of RC=CRC(O)CH2C(O) (where R = p-tolylthio) was solved by X-ray crystallography. 4,5-Bis(p-tolylthio)-4-cyclopenten-1,3-dione crystallizes in the monoclinic space group P2
1/c, a = 14.203(3) Å, b = 6.181(1) Å, c = 20.372(4) Å, = 106.111(3)°, V = 1718.1(6) Å3, Z = 4, and d
calc = 1.316 mg/m3; R = 0.0743, R
w = 0.1693 for 3958 reflections with I > 2(I). The redox properties of 4,5-bis(p-tolylthio)-4-cyclopenten-1,3-dione have been examined by cyclic voltammetry in CH2Cl2 solution, where a quasireversible reduction wave at –1.10 V was found. The reduction behavior is discussed relative to the nature of the LUMO level, which has been determined by extended Hückel MO calculations. The redox chemistry and the LUMO of our bidentate sulfide ligand are contrasted with the known redox chemistry and the LUMO composition of the corresponding bidentate phosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd). 相似文献
1000.
Ö. Nilgün Akkuş Andreas Decken Carsten Knapp Jack Passmore 《Journal of chemical crystallography》2006,36(5):321-329
[Zn(SO2)2][AsF6]2 (1) has been prepared from zinc metal and AsF5 in liquid sulfur dioxide, and crystallized from sulfur dioxide giving crystals of [Zn(SO2)4(AsF6)2] (1a). The compound 1 forms the homoleptic complexes [Zn(NCR)6](AsF6)2 (R: CH3 (2a), C6H5 (3a), C6F5 (3b)) with the corresponding nitriles. In these complexes, the metal center is octahedrally surrounded by six ligands (average Zn–N 2.13 ?). Reaction of 1 with the weaker ligand F3CCN results in dicoordination at the metal center complemented by a two-dimensional polymeric network (2b) containing bridging AsF6
− anions. [Zn(SO2)4(AsF6)2] (1a): monoclinic, P21/c, a=8.5176(8) ?, b=13.5787(14) ?, c=14.7661(15) ?, β=99.296(2)°; [Zn(NCCH3)6][AsF6]2
(2a): rhombohedral, R-3, a=11.2225(8) ?, b=11.2225(8) ?, c=16.9393(14) ?; [Zn (NCCF3)2][μ-FAsF5)2( (2b): monoclinic, P21/c, a=11.226(3) ?, b=6.6147(19) ?, c=10.460(3) ?, β=104.028(5)°; [Zn(NCC6H5)6][AsF6]2 (3a): monoclinic, P21/n, a=13.7968(10) ?, b=19.8861(15) ?, c=16.1692(12) ?, β=91.563(2)°; [Zn(NCC6F5)6][AsF6]2·2SO2 (3b): monoclinic, P21/n, a=10.8448(9) ?, b=154456(13) ?, c=17.5206(15) ?, β=104.158(1)°. 相似文献