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141.
Guozhu Li Qinzhe Liu Laxmaiah Vasamsetty Weicong Guo Prof. Dr. Jun Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(9):3503-3507
A ruthenium(II)-catalyzed asymmetric intramolecular hydroarylation assisted by a chiral transient directing group has been developed. A series of 2,3-dihydrobenzofurans bearing chiral all-carbon quaternary stereocenters have been prepared in remarkably high yields (up to 98 %) and enantioselectivities (up to >99 % ee). By this methodology, a novel asymmetric total synthesis of CB2 receptor agonist MDA7 has been successfully developed. 相似文献
142.
Dr. Kang Cheng Lars I. van der Wal Dr. Hideto Yoshida Jogchum Oenema Dr. Justine Harmel Dr. Zhaorong Zhang Dr. Glenn Sunley Dr. Jovana Zečević Prof. Krijn P. de Jong 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(9):3620-3628
Improving product selectivity by controlling the spatial organization of functional sites at the nanoscale is a critical challenge in bifunctional catalysis. We present a series of composite bifunctional catalysts consisting of one-dimensional zeolites (ZSM-22 and mordenite) and a γ-alumina binder, with platinum particles controllably deposited either on the alumina binder or inside the zeolite crystals. The hydroisomerization of n-heptane demonstrates that the catalysts with platinum particles on the binder, which separates platinum and acid sites at the nanoscale, leads to a higher yield of desired isomers than catalysts with platinum particles inside the zeolite crystals. Platinum particles within the zeolite crystals impose pronounced diffusion limitations on reaction intermediates, which leads to secondary cracking reactions, especially for catalysts with narrow micropores or large zeolite crystals. These findings extend the understanding of the “intimacy criterion” for the rational design of bifunctional catalysts for the conversion of low-molecular-weight reactants. 相似文献
143.
Tzu-Yu Chen Jinfeng Chen Yijie Tang Dr. Jiahai Zhou Dr. Yisong Guo Dr. Wei-chen Chang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(19):7437-7441
N-alkylisonitrile, a precursor to isonitrile-containing lipopeptides, is biosynthesized by decarboxylation-assisted -N≡C group (isonitrile) formation by using N-alkylglycine as the substrate. This reaction is catalyzed by iron(II) and 2-oxoglutarate (Fe/2OG) dependent enzymes. Distinct from typical oxygenation or halogenation reactions catalyzed by this class of enzymes, installation of the isonitrile group represents a novel reaction type for Fe/2OG enzymes that involves a four-electron oxidative process. Reported here is a plausible mechanism of three Fe/2OG enzymes, Sav607, ScoE and SfaA, which catalyze isonitrile formation. The X-ray structures of iron-loaded ScoE in complex with its substrate and the intermediate, along with biochemical and biophysical data reveal that -N≡C bond formation involves two cycles of Fe/2OG enzyme catalysis. The reaction starts with an FeIV-oxo-catalyzed hydroxylation. It is likely followed by decarboxylation-assisted desaturation to complete isonitrile installation. 相似文献
144.
Le' an Hu Yao Zhang Qing-Wen Zhang Qin Yin Xumu Zhang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(13):5359-5363
A Ru-catalyzed direct asymmetric reductive amination of ortho-OH-substituted diaryl and sterically hindered ketones with ammonium salts is reported. This method represents a straightforward route toward the synthesis of synthetically useful chiral primary diarylmethylamines and sterically hindered benzylamines (up to 97 % yield, 93–>99 % ee). Elaborations of the chiral amine products into bioactive compounds and a chiral ligand were demonstrated through manipulation of the removable and convertible -OH group. 相似文献
145.
Arnar Guðmundsson Kim Elisabeth Schlipköter Prof. Dr. Jan-E. Bäckvall 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(13):5441-5444
We report the first FeII-catalyzed biomimetic aerobic oxidation of alcohols. The principle of this oxidation, which involves several electron-transfer steps, is reminiscent of biological oxidation in the respiratory chain. The electron transfer from the alcohol to molecular oxygen occurs with the aid of three coupled catalytic redox systems, leading to a low-energy pathway. An iron transfer-hydrogenation complex was utilized as a substrate-selective dehydrogenation catalyst, along with an electron-rich quinone and an oxygen-activating Co(salen)-type complex as electron-transfer mediators. Various primary and secondary alcohols were oxidized in air to the corresponding aldehydes or ketones with this method in good to excellent yields. 相似文献
146.
147.
Linli Zhang Yitian Tang Zhaobin Han Kuiling Ding 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(15):5027-5031
A series of MnI complexes containing lutidine‐based chiral pincer ligands with modular and tunable structures has been developed. The complex shows unprecedentedly high activities (up to 9800 TON; TON=turnover number), broad substrate scope (81 examples), good functional‐group tolerance, and excellent enantioselectivities (85–98 % ee) in the hydrogenation of various ketones. These aspects are rare in earth‐abundant metal catalyzed hydrogenations. The utility of the protocol have been demonstrated in the asymmetric synthesis of a variety of key intermediates for chiral drugs. Preliminary mechanistic investigations indicate that an outer‐sphere mode of substrate–catalyst interactions probably dominates the catalysis. 相似文献
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150.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(39):12053-12057
The synthesis of unsymmetrical cyclobutanes by controlled heterodimerization of olefins remains a substantial challenge, particularly in an enantiocontrolled fashion. Shown herein is that chiral Lewis acid catalyzed triplet sensitization enables the synthesis of highly enantioenriched diarylcyclobutanes by photocycloaddition of structurally varied 2′‐hydroxychalcones with a range of styrene coupling partners. The utility of this reaction is demonstrated through the direct synthesis of a representative norlignan cyclobutane natural product. 相似文献