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Dr. Michael Brown Dr. Ravi Kumar Dr. Julia Rehbein Prof. Dr. Thomas Wirth 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(12):4030-4035
A stereoselective hypervalent iodine‐promoted oxidative rearrangement of 1,1‐disubstituted alkenes has been developed. This practically simple protocol provides access to enantioenriched α‐arylated ketones without the use of transition metals from readily accessible alkenes. 相似文献
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Dr. Alejandro Parra Dr. Silvia Reboredo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(51):17244-17260
Chiral hypervalent iodine chemistry has been steadily increasing in importance in recent years. This review catalogues enantioselective transformations triggered by chiral hypervalent iodine(III/V) reagents, in stoichiometric or catalytic quantities, highlighting the different reactivities in terms of yield and enantioselectivity. Moreover, the synthesis of the most remarkable and successful catalysts has been illustrated in detail. 相似文献
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Chemo‐, Diastereo‐, and Enantioselective Iridium‐Catalyzed Allylic Intramolecular Dearomatization Reaction of Naphthol Derivatives 下载免费PDF全文
Qiang Cheng Ye Wang Prof. Dr. Shu‐Li You 《Angewandte Chemie (International ed. in English)》2016,55(10):3496-3499
An iridium‐catalyzed intramolecular asymmetric allylic dearomatization reaction of naphthol derivatives is described. Challenges confronted in this reaction include chemoselectivity between carbon and oxygen atoms as nucleophilic centers, diastereoselectivity when contiguous chiral centers are generated, and enantioselective control for constructing an all‐carbon quaternary stereocenter. In the presence of an iridium catalyst generated from [{Ir(dbcot)Cl}2] (dbcot=dibenzocyclooctatetraene) and a new THQphos (tetrahydroquinolinedinaphthophosphoramidite) ligand, various spironaphthalenones were obtained with up to greater than 95:5 C/O selectivity, greater than 95:5 d.r., and 99 % ee, thus providing a general method for the dearomatization of naphthols. 相似文献
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Dual Hypervalent Iodine(III) Reagents and Photoredox Catalysis Enable Decarboxylative Ynonylation under Mild Conditions 下载免费PDF全文
Hanchu Huang Guojin Zhang Prof. Dr. Yiyun Chen 《Angewandte Chemie (International ed. in English)》2015,54(27):7872-7876
A combination of hypervalent iodine(III) reagents (HIR) and photoredox catalysis with visible light has enabled chemoselective decarboxylative ynonylation to construct ynones, ynamides, and ynoates. This ynonylation occurs effectively under mild reaction conditions at room temperature and on substrates with various sensitive and reactive functional groups. The reaction represents the first HIR/photoredox dual catalysis to form acyl radicals from α‐ketoacids, followed by an unprecedented acyl radical addition to HIR‐bound alkynes. Its efficient construction of an mGlu5 receptor inhibitor under neutral aqueous conditions suggests future visible‐light‐induced biological applications. 相似文献
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An important contribution to enzyme catalysis may be made by cooperative effects—which are induced by the interactions of a negatively charged ligand L with peptide hydrogen bond networks—through stabilization of charge formation along the reaction pathway. This has been found from density functional calculations on model systems for peptide hydrogen bond networks (an example is shown in the picture). 相似文献
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Pioneering Metal‐Free Oxidative Coupling Strategy of Aromatic Compounds Using Hypervalent Iodine Reagents 下载免费PDF全文
We started our hypervalent iodine research about 30 years ago in the mid‐1980s. We soon successfully developed the single‐electron‐transfer oxidation ability of a hypervalent iodine reagent, specifically, phenyliodine(III) bis(trifluoroacetate) (PIFA), toward aromatic rings of phenyl ethers for forming aromatic cation radicals. This was one of the exciting and unexpected events in our research studies so far, and the discovery was reported in 1991. It also led to the next challenge, developing the metal‐free oxidative couplings for C–H functionalizations and direct couplings between the C–H bonds of valuable aromatic compounds in organic synthesis. In order to realize the effective oxidative coupling, pioneering new aromatic ring activations was essential and several useful methodologies have been found for oxidizable arenes. The achievements regarding this objective obtained in our continuous research are herein summarized with classification of the aromatic ring activation strategies. 相似文献
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Tummanapalli Satyanarayana Dr. Susan Abraham Dr. Henri B. Kagan Prof. 《Angewandte Chemie (International ed. in English)》2009,48(3):456-494
There is a need for the preparation of enantiomerically pure compounds for various applications. An efficient approach to achieve this goal is asymmetric catalysis. The chiral catalyst is usually prepared from a chiral auxiliary, which itself is derived from a natural product or by resolution of a racemic precursor. The use of non‐enantiopure chiral auxiliaries in asymmetric catalysis seems unattractive to preparative chemists, since the anticipated enantiomeric excess (ee) of the reaction product should be proportional to the ee value of the chiral auxiliary (linearity). In fact, some deviation from linearity may arise. Such nonlinear effects can be rich in mechanistic information and can be synthetically useful (asymmetric amplification). This Review documents the advances made during the last decade in the use of nonlinear effects in the area of organometallic and organic catalysis. 相似文献
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The utilization of hydrogen bonding as an activation force has become a powerful tool in asymmetric organocatalysis. Significant advances have been made in the recent past in this emerging field. Due to space constraints, this Focus Review summarizes only the key aspects with an emphasis on catalysis based on chiral ureas and thioureas, diols, and phosphoric acids. The examples provided neatly demonstrate that chiral ureas and thioureas, diols, and phosphoric acids display effective and unique activation modes of catalysis for a broad spectrum of asymmetric organic transformations, including single‐step and multiple‐step cascade reactions. These functionalities, which have the ability to afford efficient H‐bond activation of electrophiles including C?O, C?N, aziridines, and epoxides, have established their status as “privileged” functional groups in the design of organocatalysts. 相似文献
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Mohamed Elsherbini Bethan Winterson Haifa Alharbi Ana A. Folgueiras‐Amador Clina Gnot Thomas Wirth 《Angewandte Chemie (International ed. in English)》2019,58(29):9811-9815
An efficient and reliable electrochemical generator of hypervalent iodine reagents has been developed. In the anodic oxidation of iodoarenes to hypervalent iodine reagents under flow conditions, the use of electricity replaces hazardous and costly chemical oxidants. Unstable hypervalent iodine reagents can be prepared easily and coupled with different substrates to achieve oxidative transformations in high yields. The unstable, electrochemically generated reagents can also easily be transformed into classic bench‐stable hypervalent iodine reagents through ligand exchange. The combination of electrochemical and flow‐chemistry advantages largely improves the ecological footprint of the overall process compared to conventional approaches. 相似文献
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Asymmetric Hydroxylative Phenol Dearomatization Promoted by Chiral Binaphthylic and Biphenylic Iodanes 下载免费PDF全文
Cyril Bosset Romain Coffinier Dr. Philippe A. Peixoto Mourad El Assal Dr. Karinne Miqueu Dr. Jean‐Marc Sotiropoulos Dr. Laurent Pouységu Prof. Stéphane Quideau 《Angewandte Chemie (International ed. in English)》2014,53(37):9860-9864
The long‐standing quest for chiral hypervalent organoiodine compounds (i.e., iodanes) as metal‐free reagents for asymmetric synthesis continues. Although remarkable progress has recently been made in organoiodine‐catalyzed reactions using a terminal oxidant in stoichiometric amounts, there is still a significant need for “flaskable” chiral iodane reagents. Herein, we describe the synthesis of new iodobinaphthyls and iodobiphenyls, their successful and selective DMDO‐mediated oxidation into either λ3‐ or λ5‐iodanes, and the evaluation of their capacity to promote asymmetric hydroxylative phenol dearomatization (HPD) reactions. Most notably, a C2‐symmetrical biphenylic λ5‐iodane promoted the HPD‐induced conversion of the monoterpene thymol into the corresponding ortho‐quinol‐based [4+2] cyclodimer (i.e., bis(thymol)) with enantiomeric excesses of up to 94 %. 相似文献