共查询到20条相似文献,搜索用时 0 毫秒
1.
2.
Boron Lewis Acid‐Catalyzed Hydroboration of Alkenes with Pinacolborane: BArF3 Does What B(C6F5)3 Cannot Do!
下载免费PDF全文
Dr. Qin Yin Dr. Hendrik F. T. Klare Prof. Dr. Martin Oestreich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(39):13840-13844
The transition‐metal‐free hydroboration of various alkenes with pinacolborane (HBpin) initiated by tris[3,5‐bis(trifluoromethyl)phenyl]borane (BArF3) is reported. The choice of the boron Lewis acid is crucial as the more prominent boron Lewis acid tris(pentafluorophenyl)borane (B(C6F5)3) is reluctant to react. Unlike B(C6F5)3, BArF3 is found to engage in substituent redistribution with HBpin, resulting in the formation of ArFBpin and the electron‐deficient diboranes [H2BArF]2 and [(ArF)(H)B(μ‐H)2BArF2]. These in situ‐generated hydroboranes undergo regioselective hydroboration of styrene derivatives as well as aliphatic alkenes with cis diastereoselectivity. Another ligand metathesis of these adducts with HBpin subsequently affords the corresponding HBpin‐derived anti‐Markovnikov adducts. The reactive hydroboranes are regenerated in this step, thereby closing the catalytic cycle. 相似文献
3.
4.
Laura Bini Evgeny A. Pidko Dr. Christian Müller Dr. Rutger A. van Santen Prof. Dr. Dieter Vogt Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(35):8768-8778
According to present knowledge, the Ni‐catalyzed hydrocyanation of styrene leads predominantly to the branched product 2‐phenylpropionitrile (98 %). We observed a dramatic inversion of the regioselectivity upon addition of a Lewis acid. Up to 83 % of the linear product 3‐phenylpropionitrile was obtained by applying phosphite ligands in the presence of AlCl3. The mechanism of the Ni‐catalyzed reaction and the influence of additional Lewis acids have been investigated by means of deuterium labeling experiments, NMR studies, and DFT calculations. Furthermore, the behavior of different Lewis acids, such as CuCN, could be rationalized and predicted by DFT calculations. 相似文献
5.
B(C6F5)3‐Catalyzed Transfer Hydrogenation of Imines and Related Heteroarenes Using Cyclohexa‐1,4‐dienes as a Dihydrogen Source 下载免费PDF全文
Dr. Indranil Chatterjee Prof. Dr. Martin Oestreich 《Angewandte Chemie (International ed. in English)》2015,54(6):1965-1968
The strong boron Lewis acid tris(pentafluorophenyl)borane, B(C6F5)3, is shown to abstract a hydride from suitably donor‐substituted cyclohexa‐1,4‐dienes, eventually releasing dihydrogen. This process is coupled with the FLP‐type (FLP=frustrated Lewis pair) hydrogenation of imines and nitrogen‐containing heteroarenes that are catalyzed by the same Lewis acid. The net reaction is a B(C6F5)3‐catalyzed, i.e., transition‐metal‐free, transfer hydrogenation using easy‐to‐access cyclohexa‐1,4‐dienes as reducing agents. Competing reaction pathways with or without the involvement of free dihydrogen are discussed. 相似文献
6.
Enantioselective Nazarov Cyclizations Catalyzed by an Axial Chiral C6F5‐Substituted Boron Lewis Acid 下载免费PDF全文
Lars Süsse Maria Vogler Dr. Marius Mewald Dr. Benedict Kemper Dr. Elisabeth Irran Prof. Dr. Martin Oestreich 《Angewandte Chemie (International ed. in English)》2018,57(35):11441-11444
A chiral variant of B(C6F5)3 with a 3,3′‐disubstituted binaphthyl backbone is shown to catalyze Nazarov cyclizations with high levels of enantio‐ and diastereocontrol. The parent B(C6F5)3 also promotes these ring closures efficiently. This electrocyclization is another example of the still small family of C?C bond formations mediated by B(C6F5)3 as the catalyst. 相似文献
7.
Lewis Acid Promoted Ruthenium(II)‐Catalyzed Etherifications by Selective Hydrogenation of Carboxylic Acids/Esters 下载免费PDF全文
Dr. Yuehui Li Dr. Christoph Topf Dr. Xinjiang Cui Dr. Kathrin Junge Prof. Dr. Matthias Beller 《Angewandte Chemie (International ed. in English)》2015,54(17):5196-5200
Ethers are of fundamental importance in organic chemistry and they are an integral part of valuable flavors, fragrances, and numerous bioactive compounds. In general, the reduction of esters constitutes the most straightforward preparation of ethers. Unfortunately, this transformation requires large amounts of metal hydrides. Presented herein is a bifunctional catalyst system, consisting of Ru/phosphine complex and aluminum triflate, which allows selective synthesis of ethers by hydrogenation of esters or carboxylic acids. Different lactones were reduced in good yields to the desired products. Even challenging aromatic and aliphatic esters were reduced to the desired products. Notably, the in situ formed catalyst can be reused several times without any significant loss of activity. 相似文献
8.
Chiral Nanoparticles/Lewis Acids as Cooperative Catalysts for Asymmetric 1,4‐Addition of Arylboronic Acids to α,β‐Unsaturated Amides 下载免费PDF全文
Dr. Tomohiro Yasukawa Yuuki Saito Dr. Hiroyuki Miyamura Prof. Dr. Shū Kobayashi 《Angewandte Chemie (International ed. in English)》2016,55(28):8058-8061
Cooperative catalysts consisting of chiral Rh/Ag nanoparticles and Sc(OTf)3 have been developed that catalyze asymmetric 1,4‐addition reactions of arylboronic acids with α,β‐unsaturated amides efficiently. The reaction has been considered one of the most challenging reactions because of the low reactivity of the amide substrates. The new catalysts provide the desired products with outstanding enantioselectivities (>98 % ee) in the presence of low loadings (<0.5 mol %) of the catalyst. 相似文献
9.
Sulfonated carbonaceous solid acid was prepared straightforwardly from household granulated sucrose through a one‐pot carbonization—sulfonation process. The performance of this solid Brønsted acid was tested by the 1,1‐diacylation of aldehydes. Lewis acid, such as indium chloride, was supported on sucrose‐derived carbonaceous solid acid through anion metathesis and successfully applied to the conjugate addition of indole to α,β‐unsaturated ketones. 相似文献
10.
Prof. Sławomir J. Grabowski 《Chemphyschem》2015,16(7):1470-1479
MP2/aug‐cc‐pVTZ calculations were performed on complexes of boron and aluminum trihydrides and trihalides with hydrogen cyanide (ZH3‐NCH and ZX3‐NCH; Z=B, Al; X=F, Cl). The complexes are linked through the B???N and Al???N interactions, which are named as triel bonds and which are classified as π‐hole bonds. It was found that they possess numerous characteristics of typical covalent bonds, since they are ruled mainly by processes of the electron charge shift from the Lewis base to the Lewis acid unit. Other configurations of the ZH3‐NCH and ZX3‐NCH complexes linked by the dihydrogen, hydrogen, and halogen bonds were found. However, these interactions are much weaker than the corresponding π‐hole bonds. The quantum theory of atoms in molecules and the natural bond orbital approaches were applied to characterize the complexes and interactions analyzed. The crystal structures of triel trihydrides and triel trihalides were also analyzed for comparison with the results of calculations. 相似文献
11.
Jens Mohr Prof. Dr. Martin Oestreich 《Angewandte Chemie (International ed. in English)》2014,53(48):13278-13281
The hydrogenation of oximes and oxime ethers is usually hampered by N? O bond cleavage, hence affording amines rather than hydroxylamines. The boron Lewis acid B(C6F5)3 is found to catalyze the chemoselective hydrogenation of oxime ethers at elevated or even room temperature under 100 bar dihydrogen pressure. The use of the triisopropylsilyl group as a protecting group allows for facile liberation of the free hydroxylamines. 相似文献
12.
Dr. Indranil Chatterjee Dr. Zheng‐Wang Qu Prof. Dr. Stefan Grimme Prof. Dr. Martin Oestreich 《Angewandte Chemie (International ed. in English)》2015,54(41):12158-12162
A transition‐metal‐free transfer hydrogenation of 1,1‐disubstituted alkenes with cyclohexa‐1,4‐dienes as the formal source of dihydrogen is reported. The process is initiated by B(C6F5)3‐mediated hydride abstraction from the dihydrogen surrogate, forming a Brønsted acidic Wheland complex and [HB(C6F5)3]?. A sequence of proton and hydride transfers onto the alkene substrate then yields the alkane. Although several carbenium ion intermediates are involved, competing reaction channels, such as dihydrogen release and cationic dimerization of reactants, are largely suppressed by the use of a cyclohexa‐1,4‐diene with methyl groups at the C1 and C5 as well as at the C3 position, the site of hydride abstraction. The alkene concentration is another crucial factor. The various reaction pathways were computationally analyzed, leading to a mechanistic picture that is in full agreement with the experimental observations. 相似文献
13.
14.
Rhodium‐Catalyzed Asymmetric Arylation of β,γ‐Unsaturated α‐Ketoamides for the Construction of Nonracemic γ,γ‐Diarylcarbonyl Compounds 下载免费PDF全文
Dr. Juanjuan Wang Dr. Min Wang Prof. Dr. Peng Cao Liyin Jiang Dr. Guihua Chen Prof. Dr. Jian Liao 《Angewandte Chemie (International ed. in English)》2014,53(26):6673-6677
A highly regio‐ and enantioselective rhodium‐catalyzed 1,4‐addition of arylboronic acids to β,γ‐unsaturated α‐ketoamides using a simple new chiral sulfinylphosphine ligand is described. This transformation provides an attractive approach to construct chiral nonracemic γ,γ‐diarylsubstituted carbonyl compounds, as exemplified in the concise syntheses of sertraline and tetrahydroquinoline‐2‐carboxylamide. 相似文献
15.
Enantioselective Palladium‐Catalyzed Oxidative β,β‐Fluoroarylation of α,β‐Unsaturated Carbonyl Derivatives 下载免费PDF全文
Javier Miró Dr. Carlos del Pozo Prof. F. Dean Toste Prof. Santos Fustero 《Angewandte Chemie (International ed. in English)》2016,55(31):9045-9049
The site‐selective palladium‐catalyzed three‐component coupling of deactivated alkenes, arylboronic acids, and N‐fluorobenzenesulfonimide is disclosed herein. The developed methodology establishes a general, modular, and step‐economical approach to the stereoselective β‐fluorination of α,β‐unsaturated systems. 相似文献
16.
17.
Palladium‐Catalyzed [3+3] Annulation between Diarylamines and α,β‐Unsaturated Acids through CH Activation: Direct Access to 4‐Substituted 2‐Quinolinones 下载免费PDF全文
Dr. Rajesh Kancherla Togati Naveen Prof. Debabrata Maiti 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(23):8360-8364
A C?H activation strategy has been successfully employed for the high‐yielding synthesis of a diverse array of 4‐substituted 2‐quinolinone species by a palladium‐catalyzed dehydrogenative coupling involving diarylamines. This intermolecular annulation approach incorporates readily available α,β‐unsaturated carboxylic acids as the coupling partner by suppressing the facile decarboxylation. Based on preliminary mechanistic studies, a reaction sequence is proposed, involving ortho palladation, π‐coordination, β‐migratory insertion, and β‐hydride elimination. 相似文献
18.
19.
Extending the Scope of the B(C6F5)3‐Catalyzed CN Bond Reduction: Hydrogenation of Oxime Ethers and Hydrazones 下载免费PDF全文
Jens Mohr Digvijay Porwal Dr. Indranil Chatterjee Prof. Dr. Martin Oestreich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(49):17583-17586
The B(C6F5)3‐catalyzed hydrogenation is applied to aldoxime triisopropylsilyl ethers and hydrazones bearing an easily removable phthaloyl protective group. The C?N reduction of aldehyde‐derived substrates (oxime ethers and hydrazones) is enabled by using 1,4‐dioxane as the solvent known to participate as the Lewis‐basic component in FLP‐type heterolytic dihydrogen splitting. More basic ketone‐derived hydrazones act as Lewis bases themselves in the FLP‐type dihydrogen activation and are therefore successfully hydrogenated in nondonating toluene. The difference in reactivity between aldehyde‐ and ketone‐derived substrates is also reflected in the required catalyst loading and dihydrogen pressure. 相似文献
20.
γ‐, Diastereo‐, and Enantioselective Addition of MEMO‐Substituted Allylboron Compounds to Aldimines Catalyzed by Organoboron–Ammonium Complexes 下载免费PDF全文
Ryan J. Morrison Prof. Amir H. Hoveyda 《Angewandte Chemie (International ed. in English)》2018,57(36):11654-11661
The first catalytic, broadly applicable, efficient, γ‐, diastereo‐, and enantioselective method for addition of O‐substituted allyl‐B(pin) compounds to phosphinoylimines (MEM=methoxyethoxymethyl, pin=pinacolato) is presented. The identity of the most effective catalyst and the optimal protecting group for the organoboron reagent were determined by consideration of the steric and electronic requirements at different stages of the catalytic cycle, namely, the generation of the chiral allylboronate, the subsequent 1,3‐borotropic shift, and the addition step. Aryl‐, heteroaryl‐, alkenyl‐ and alkyl‐substituted vicinal phosphinoylamido MEM‐ethers were thus accessed in 57–92 % yield, 89:11 to >98:2 γ:α selectivity, 76:24–97:3 diastereomeric ratio, and 90:10–99:1 enantiomeric ratio. The method is scalable, and the phosphinoyl and MEM groups may be removed selectively or simultaneously. Utility is highlighted by enantioselective synthesis of an NK‐1 receptor antagonist. 相似文献