共查询到20条相似文献,搜索用时 15 毫秒
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Dr. Maialen Espinal‐Viguri Callum R. Woof Dr. Ruth L. Webster 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(33):11605-11608
Iron‐catalyzed hydroboration (HB) of alkenes and alkynes is reported. A simple change in ligand structure leads to an extensive change in catalyst activity. Reactions proceed efficiently over a wide range of challenging substrates including activated, unactivated and sterically encumbered motifs. Conditions are mild and do not require the use of reducing agents or other additives. Large excesses of borating reagent are not required, allowing control of chemo‐ and regioselectivity in the presence of multiple double bonds. Mechanistic insight reveals that the reaction is likely to proceed via a highly reactive iron hydride intermediate. 相似文献
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Several cobalt complexes bearing tridentate (NNN) ligands were synthesized and served as precatalysts for alkyne hydrosilylation with Ph2SiH2. For terminal alkynes, the catalyst L2 b‐CoCl2 was selected, and resulted in the corresponding α‐vinylsilanes with high (Markovnikov) regioselectivity and extensive functional‐group tolerance. For internal diaryl alkynes, the catalyst L2 c‐CoCl2 exhibited the best activity, and afforded E‐selective vinylsilanes through syn‐addition in excellent yield under mild conditions. 相似文献
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Jinhu Wei Liangliang Wu Hai‐Xu Wang Xiting Zhang Chun‐Wai Tse Cong‐Ying Zhou Jie‐Sheng Huang Chi‐Ming Che 《Angewandte Chemie (International ed. in English)》2020,59(38):16561-16571
Reliable methods for enantioselective cis‐dihydroxylation of trisubstituted alkenes are scarce. The iron(II) complex cis‐α‐[FeII(2‐Me2‐BQPN)(OTf)2], which bears a tetradentate N4 ligand (Me2‐BQPN=(R,R)‐N,N′‐dimethyl‐N,N′‐bis(2‐methylquinolin‐8‐yl)‐1,2‐diphenylethane‐1,2‐diamine), was prepared and characterized. With this complex as the catalyst, a broad range of trisubstituted electron‐deficient alkenes were efficiently oxidized to chiral cis‐diols in yields of up to 98 % and up to 99.9 % ee when using hydrogen peroxide (H2O2) as oxidant under mild conditions. Experimental studies (including 18O‐labeling, ESI‐MS, NMR, EPR, and UV/Vis analyses) and DFT calculations were performed to gain mechanistic insight, which suggested possible involvement of a chiral cis‐FeV(O)2 reaction intermediate as an active oxidant. This cis‐[FeII(chiral N4 ligand)]2+/H2O2 method could be a viable green alternative/complement to the existing OsO4‐based methods for asymmetric alkene dihydroxylation reactions. 相似文献
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Conversion of Olefins into Ketones by an Iron‐Catalyzed Wacker‐type Oxidation Using Oxygen as the Sole Oxidant
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Florian Puls Prof. Dr. Hans‐Joachim Knölker 《Angewandte Chemie (International ed. in English)》2018,57(5):1222-1226
We describe a mild and operationally simple procedure for the oxidation of olefins into ketones. The reaction is catalyzed by the hexadecafluorinated iron–phthalocyanine complex FePcF16 with stoichiometric amounts of triethylsilane as an additive under oxygen atmosphere to give ketones in good to high yields with excellent chemoselectivity and functional group tolerance. Ketone formation proceeds in up to 95 % yield and with 100 % regioselectivity while the corresponding alcohols were observed as side products. 相似文献
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Highly Chemo‐, Regio‐, and Stereoselective Cobalt‐Catalyzed Markovnikov Hydrosilylation of Alkynes 下载免费PDF全文
A highly chemo‐, regio‐ and stereoselective cobalt‐catalyzed Markovnikov hydrosilylation of alkynes was developed. Various functionalized groups, such as halides, free alcohols, free aniline, ketones, esters, amides, and nitriles are tolerated, which may lead to further applications and late‐stage derivatizations. To date, this is the most efficient cobalt catalytic system (TOF=65 520 h?1; TOF=turnover frequency) for hydrosilylation of alkynes. The Hiyama–Denmark cross‐coupling reactions of vinylsilanes with aryl iodides underwent smoothly to afford 1,1‐diarylethenes. A unique regioselectivity‐controllable hydrosilylation/hydroboration reaction of alkynes was also described. 相似文献
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Naohisa Nakagawa Prof. Dr. Takuji Hatakeyama Prof. Dr. Masaharu Nakamura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(11):4257-4261
An iron‐catalyzed diboration reaction of alkynes with bis(pinacolato)diboron (B2pin2) and external borating agents (MeOB(OR)2) affords diverse symmetrical or unsymmetrical cis‐1,2‐diborylalkenes. The simple protocol for the diboration reaction can be extended to the iron‐catalyzed carboboration of alkynes with primary and, unprecedentedly, secondary alkyl halides, affording various tetrasubstituted monoborylalkenes in a highly stereoselective manner. DFT calculations indicate that a boryliron intermediate adds across the triple bond of an alkyne to afford an alkenyliron intermediate, which can react with the external trapping agents, borates and alkyl halides. In situ trapping experiments support the intermediacy of the alkenyl iron species using radical probe stubstrates. 相似文献
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Copper‐Catalyzed Synthesis of 1,1‐Diborylalkanes through Regioselective Dihydroboration of Terminal Alkynes 下载免费PDF全文
The copper‐catalyzed sequential hydroboration of terminal alkynes with pinacolborane to prepare 1,1‐diborylalkanes directly from alkynes was studied. Protected propargyl amines, propargyl alcohol derivatives, and simple alkynes regioselectively produced the desired 1,1‐diborylalkanes in good yields with a copper/xantphos catalyst. 相似文献
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Dr. Junliang Wu Prof. Naohiko Yoshikai 《Angewandte Chemie (International ed. in English)》2016,55(1):336-340
While transition metal catalyzed addition reactions of arylmetal reagents to unfunctionalized alkynes have been extensively developed in the last decade, analogous reactions using alkenylmetal reagents remain rare regardless of their potential utility for the synthesis of unsymmetrical 1,3‐dienes. Reported herein is the development of a cobalt/diphosphine catalyst which promotes efficient and stereoselective addition of alkenylzinc reagents to unfunctionalized internal alkynes. The resulting dienylzinc species serve as versatile intermediates for further synthetic transformations. 相似文献
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Yubo Pang Gengtu Liu Congcong Huang Xiang‐Ai Yuan Weipeng Li Jin Xie 《Angewandte Chemie (International ed. in English)》2020,59(31):12789-12794
We have developed a general and site‐predictable manganese‐catalyzed hydroarylation of internal alkynes in the presence of water, under an air atmosphere without the involvement of ligand. The unique catalytic feature of this reaction is highlighted by comparison with other widely used transition metal catalysts including palladium, rhodium, nickel, or copper. The simple operation, high efficiency and excellent functional group compatibility make this protocol practical for more than 90 structurally diverse internal alkynes, overcoming the influence of both electronic and steric effect of alkynes. Its exclusive regio‐ and chemoselectivity originates from the unique reactivity of the manganese‐based catalyst towards an inherent double controlled strategy of sterically hindered propargyl alcohols without the installing of external directing groups. Its synthetic robustness and practicality have been illustrated by the concise synthesis of bervastatin, a hypolipidemic drug, and late‐stage modification of complex alkynes with precise regioselectivity. 相似文献
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Didecarboxylative Iron‐Catalyzed Bidirectional Aldolization towards Diversity‐Oriented Ketodiol Synthesis 下载免费PDF全文
Adrien Quintard Jean Rodriguez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(42):14717-14722
1,3‐Acetonedicarboxylic acid was selectively activated by Fe(acac)3, providing a synthetic platform for rapid synthesis of keto‐3,3′‐diols. The bidirectional aldol reaction was efficient for challenging aliphatic aldehydes, providing a rapid route to potentially bioactive complex structures. 相似文献
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Synthesis of 2‐Alkynoates by Palladium(II)‐Catalyzed Oxidative Carbonylation of Terminal Alkynes and Alcohols 下载免费PDF全文
Qun Cao N. Louise Hughes Dr. Mark J. Muldoon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(34):11982-11985
A homogeneous PdII catalyst, utilizing a simple and inexpensive amine ligand (TMEDA), allows 2‐alkynoates to be prepared in high yields by an oxidative carbonylation of terminal alkynes and alcohols. The catalyst system overcomes many of the limitations of previous palladium carbonylation catalysts. It has an increased substrate scope, avoids large excesses of alcohol substrate and uses a desirable solvent. The catalyst employs oxygen as the terminal oxidant and can be operated under safer gas mixtures. 相似文献
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Yanfeng Jiang Olivier Blacque Dr. Thomas Fox Dr. Christian M. Frech Dr. Heinz Berke Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(9):2121-2128
Choosy chemicals : Rhenium(I) complexes of type [ReBr2(L)(NO)(PR3)2] (L=H2 ( 1 ), CH3CN ( 2 ), ethylene ( 3 ); R=iPr ( a ), cyclohexyl ( b )) proved to be suitable catalyst precursors for the highly selective dehydrogenative silylation of alkenes. Two types of rhenium(I) hydride species, [ReBrH(NO)(PR3)2] ( 4 ) and [ReBr(η2‐CH2?CHR1)H(NO)(PR3)2] ( 5 ), were found in the [ReBr2(L)(NO)(PR3)2]‐catalyzed dehydrogenative silylation of alkenes.