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Dr. Samuel Stolz Dr. Aliaksandr V. Yakutovich Dr. Jan Prinz Dr. Thomas Dienel Dr. Carlo A. Pignedoli Prof. Dr. Harald Brune Dr. Oliver Gröning Dr. Roland Widmer 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(41):18336-18340
Enantioselectivity in heterogeneous catalysis strongly depends on the chirality transfer between catalyst surface and all reactants, intermediates, and the product along the reaction pathway. Herein we report the first enantioselective on-surface synthesis of molecular structures from an initial racemic mixture and without the need of enantiopure modifier molecules. The reaction consists of a trimerization via an unidentified bonding motif of prochiral 9-ethynylphenanthrene (9-EP) upon annealing to 500 K on the chiral Pd3-terminated PdGa{111} surfaces into essentially enantiopure, homochiral 9-EP propellers. The observed behavior strongly contrasts the reaction of 9-EP on the chiral Pd1-terminated PdGa{111} surfaces, where 9-EP monomers that are in nearly enantiopure configuration, dimerize without enantiomeric excess. Our findings demonstrate strong chiral recognition and a significant ensemble effect in the PdGa system, hence highlighting the huge potential of chiral intermetallic compounds for enantioselective synthesis and underlining the importance to control the catalytically active sites at the atomic level. 相似文献
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Highly Enantioselective Adsorption of Small Prochiral Molecules on a Chiral Intermetallic Compound 下载免费PDF全文
Dr. Jan Prinz Dr. Oliver Gröning Prof. Dr. Harald Brune Dr. Roland Widmer 《Angewandte Chemie (International ed. in English)》2015,54(13):3902-3906
Intrinsically chiral surfaces of intermetallic compounds are shown to be novel materials for enantioselective processes. Their advantage is the significantly higher thermal and chemical stability, and therefore their extended application range for catalyzed chiral reactions compared to surfaces templated with chiral molecular modifiers or auxiliaries. On the Pd1‐terminated PdGa(111) surface, room‐temperature adsorption of a small prochiral molecule (9‐ethynylphenanthrene) leads to exceptionally high enantiomeric excess ratios of up to 98 %. Our findings highlight the great potential of intrinsically chiral intermetallic compounds for the development of novel, enantioselective catalysts that can be operated at high temperatures and potentially also in harsh chemical environments. 相似文献
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Cyclotrimerization‐Induced Chiral Supramolecular Structures of 4‐Ethynyltriphenylamine on Au(111) Surface 下载免费PDF全文
Feifei Xiang Yan Lu Chao Li Xin Song Xiaoqing Liu Zhongping Wang Juan Liu Dr. Mingdong Dong Prof. Dr. Li Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(37):12978-12983
Cyclotrimerization‐induced chiral supramolecular structures of 4‐ethynyltriphenylamine (ETPA) have been synthesized on the Au(111) surface through alkyne‐based reactions. Whereas the ETPA molecules adsorbed on the Au(111) surface remain inert and form a close‐packed self‐assembled structure at room temperature, the combination of scanning tunneling microscopy observations and theoretical calculations unambiguously reveal that the ETPA molecules cyclotrimerize to form new trimer‐like species—1,3,5‐tris[4‐(diphenylamino)phenyl]benzene (TPAPB)—after annealing at 323 K. Further annealing drives these cyclotrimerized TPAPB molecules to form chiral hexagonal supramolecular structures with an extraordinary self‐healing ability. 相似文献
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Zhen Wang Donghui Chen Zhigang Yang Sha Bai Xiaohua Liu Dr. Lili Lin Dr. Xiaoming Feng Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(33):10130-10136
Highly enantioselective Michael addition of 1,3‐dicarbonyl compounds and nitromethane to 4‐oxo‐4‐arylbutenoates catalyzed by N,N′‐dioxide–Sc(OTf)3 complexes has been developed. Using 0.5–2 mol % catalyst loading, various α‐stereogenic esters were obtained regioselectively with excellent yields (up to 97 %) and enantioselectivities (up to >99 % ee). Moreover, the reaction performed well under nearly solvent‐free conditions. The products with functional groups are ready for further transformation, which showed the potential value of the catalytic approach. According to the experimental results and previous reports, a plausible working model has been proposed to explain the origin of the activation and the asymmetric induction. 相似文献
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《化学:亚洲杂志》2017,12(18):2335-2342
Chirality is an essential feature of asymmetric catalysts. This review summarizes asymmetric catalysts that derive their chirality exclusively from stereogenic metal centers. Reported chiral‐at‐metal catalysts can be divided into two classes, namely, inert metal complexes, in which the metal fulfills a purely structural role, so catalysis is mediated entirely through the ligand sphere, and reactive metal complexes. The latter are particularly appealing because structural simplicity (only achiral ligands) is combined with the prospect of particularly effective asymmetric induction (direct contact of the substrate with the chiral metal center). Challenges and solutions for the design of such reactive stereogenic‐only‐at‐metal asymmetric catalysts are discussed. 相似文献
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Self‐Replication and Amplification of Enantiomeric Excess of Chiral Multifunctionalized Large Molecules by Asymmetric Autocatalysis 下载免费PDF全文
Prof. Dr. Tsuneomi Kawasaki Mai Nakaoda Yutaro Takahashi Yusuke Kanto Nanako Kuruhara Kenji Hosoi Prof. Dr. Itaru Sato Arimasa Matsumoto Prof. Dr. Kenso Soai 《Angewandte Chemie (International ed. in English)》2014,53(42):11199-11202
Self‐replication of large chiral molecular architectures is one of the great challenges and interests in synthetic, systems, and prebiotic chemistry. Described herein is a new chemical system in which large chiral multifunctionalized molecules possess asymmetric autocatalytic self‐replicating and self‐improving abilities, that is, improvement of their enantioenrichment in addition to the diastereomeric ratio. The large chiral multifunctionalized molecules catalyze the production of themselves with the same structure, including the chirality of newly formed asymmetric carbon atoms, in the reaction of the corresponding achiral aldehydes and reagent. The chirality of the large multifunctionalized molecules controlled the enantioselectivity of the reaction in a highly selective manner to construct multiple asymmetric stereogenic centers in a single reaction. 相似文献
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Zhiyong Jiang Dr. Yuanyong Yang Yuanhang Pan Yujun Zhao Hongjun Liu Choon‐Hong Tan Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(19):4925-4930
Constructing α‐stereogenic amides and ketones : The highly regioselective and enantioselective conjugate addition of 1,3‐dicarbonyl compounds to 1,4‐dicarbonyl but‐2‐enes has been developed with the chiral bicyclic guanidine as catalyst (ee values up to 97 %; see scheme).
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Enantioselective Synthesis of α‐Secondary and α‐Tertiary Piperazin‐2‐ones and Piperazines by Catalytic Asymmetric Allylic Alkylation 下载免费PDF全文
Katerina M. Korch Dr. Christian Eidamshaus Dr. Douglas C. Behenna Dr. Sangkil Nam Prof. Dr. David Horne Prof. Dr. Brian M. Stoltz 《Angewandte Chemie (International ed. in English)》2015,54(1):179-183
The asymmetric palladium‐catalyzed decarboxylative allylic alkylation of differentially N‐protected piperazin‐2‐ones allows the synthesis of a variety of highly enantioenriched tertiary piperazine‐2‐ones. Deprotection and reduction affords the corresponding tertiary piperazines, which can be employed for the synthesis of medicinally important analogues. The introduction of these chiral tertiary piperazines resulted in imatinib analogues which exhibited comparable antiproliferative activity to that of their corresponding imatinib counterparts. 相似文献
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Ross A. Arthurs Dr. Muhammad Ismail Christopher C. Prior Dr. Vasily S. Oganesyan Dr. Peter N. Horton Dr. Simon J. Coles Dr. Christopher J. Richards 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(9):3065-3072
Reaction of [IrCp*Cl2]2 with ferrocenylimines (Fc=NAr, Ar=Ph, p‐MeOC6H4) results in ferrocene C?H activation and the diastereoselective synthesis of half‐sandwich iridacycles of relative configuration Sp*,RIr*. Extension to (S)‐2‐ferrocenyl‐4‐(1‐methylethyl)oxazoline gave highly diastereoselective control over the new elements of planar chirality and metal‐based pseudo‐tetrahedral chirality, to give both neutral and cationic half‐sandwich iridacycles of absolute configuration Sc,Sp,RIr. Substitution reactions proceed with retention of configuration, with the planar chirality controlling the metal‐centred chirality through an iron–iridium interaction in the coordinatively unsaturated cationic intermediate. 相似文献
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Asymmetric Ruthenium‐Catalyzed Hydrogenation of 2,6‐Disubstituted 1,5‐Naphthyridines: Access to Chiral 1,5‐Diaza‐cis‐Decalins 下载免费PDF全文
Jianwei Zhang Fei Chen Yan‐Mei He Prof. Dr. Qing‐Hua Fan 《Angewandte Chemie (International ed. in English)》2015,54(15):4622-4625
The first asymmetric hydrogenation (AH) of 2,6‐disubstituted and 2,3,6‐trisubstituted 1,5‐naphthyridines, catalyzed by chiral cationic ruthenium diamine complexes, has been developed. A wide range of 1,5‐naphthyridine derivatives were efficiently hydrogenated to give 1,2,3,4‐tetrahydro‐1,5‐naphthyridines with up to 99 % ee and full conversions. This facile and green protocol is applicable to the scaled‐up synthesis of optically pure 1,5‐diaza‐cis‐decalins, which have been used as rigid chelating diamine ligands for asymmetric synthesis. 相似文献
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Asymmetric Allylic Alkylation of β‐Ketoesters with Allylic Alcohols by a Nickel/Diphosphine Catalyst 下载免费PDF全文
Dr. Yusuke Kita Dr. Rahul D. Kavthe Hiroaki Oda Prof. Dr. Kazushi Mashima 《Angewandte Chemie (International ed. in English)》2016,55(3):1098-1101
Asymmetric allylic alkylation of β‐ketoesters with allylic alcohols catalyzed by [Ni(cod)2]/(S)‐H8‐BINAP was found to be a superior synthetic protocol for constructing quaternary chiral centers at the α‐position of β‐ketoesters. The reaction proceeded in high yield and with high enantioselectivity using various β‐ketoesters and allylic alcohols, without any additional activators. The versatility of this methodology for accessing useful and enantioenriched products was demonstrated. 相似文献
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Haizhou Huang Xiaoyan Liu Prof. Dr. Le Zhou Prof. Dr. Mingxin Chang Prof. Dr. Xumu Zhang 《Angewandte Chemie (International ed. in English)》2016,55(17):5309-5312
The highly efficient and direct asymmetric reductive amination of arylacetones catalyzed by an iridium complex for the preparation of enantiomerically pure β‐arylamines is described. The monodentate phosphoramidite ligand exhibits superb reactivity (TONs of up to 20 000) and enantioselectivity (up to 99 % ee). Additives played important roles in this reductive coupling reaction. 相似文献
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Michiko Sasaki Dr. Yuri Shirakawa Masatoshi Kawahata Dr. Kentaro Yamaguchi Prof. Dr. Kei Takeda Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(14):3363-3366
Brooked up! Treatment of (R,Z)‐3‐(tert‐butyldimethylsilyl)‐1‐cyano‐3‐hydroxyprop‐1‐enyl carbamate with a catalytic amount of a base afforded (S,E)‐3‐(tert‐butyldimethylsilyloxy)‐1‐cyanoallyl diisopropylcarbamate, showing that SE2′‐type reaction of allylsilicates proceeds in an anti fashion. The overall process is equivalent to trapping of an enantioenriched C‐chiral carbanion at the α‐position of nitrile group in up to 77 % ee (see scheme).