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1.
Palladium(0)/PAr3‐Catalyzed Intermolecular Amination of C(sp3)H Bonds: Synthesis of β‐Amino Acids
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Jian He Toshihiko Shigenari Prof. Dr. Jin‐Quan Yu 《Angewandte Chemie (International ed. in English)》2015,54(22):6545-6549
An intermolecular C(sp3)? H amination using a Pd0/PAr3 catalyst was developed. The reaction begins with oxidative addition of R2N? OBz to a Pd0/PAr3 catalyst and subsequent cleavage of a C(sp3)? H bond by the generated Pd? NR2 intermediate. The catalytic cycle proceeds without the need for external oxidants in a similar manner to the extensively studied palladium(0)‐catalyzed C? H arylation reactions. The electron‐deficient triarylphosphine ligand is crucial for this C(sp3)? H amination reaction to occur. 相似文献
2.
Li‐Jun Xiao Kai Hong Fan Luo Liang Hu William R. Ewing Kap‐Sun Yeung Jin‐Quan Yu 《Angewandte Chemie (International ed. in English)》2020,59(24):9594-9600
The use of chiral transient directing groups (TDGs) is a promising approach for developing PdII‐catalyzed enantioselective C(sp3)?H activation reactions. However, this strategy is challenging because the stereogenic center on the TDG is often far from the C?H bond, and both TDG covalently attached to the substrate and free TDG are capable of coordinating to PdII centers, which can result in a mixture of reactive complexes. We report a PdII‐catalyzed enantioselective β‐C(sp3)?H arylation reaction of aliphatic ketones using a chiral TDG. A chiral trisubstituted cyclobutane was efficiently synthesized from a mono‐substituted cyclobutane through sequential C?H arylation reactions, thus demonstrating the utility of this method for accessing structurally complex products from simple starting materials. The use of an electron‐deficient pyridone ligand is crucial for the observed enantioselectivity. Interestingly, employing different silver salts can reverse the enantioselectivity. 相似文献
3.
Palladium–N‐Heterocyclic Carbene (NHC)‐Catalyzed Asymmetric Synthesis of Indolines through Regiodivergent C(sp3)H Activation: Scope and DFT Study
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Dmitry Katayev Dr. Evgeny Larionov Dr. Masafumi Nakanishi Dr. Céline Besnard Prof. Dr. E. Peter Kündig 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(46):15021-15030
Two bulky, chiral, monodentate N‐heterocyclic carbene ligands were applied to palladium‐catalyzed asymmetric C?H arylation to incorporate C(sp3)?H bond activation. Racemic mixtures of the carbamate starting materials underwent regiodivergent reactions to afford different trans‐2,3‐substituted indolines. Although this CAr?Calkyl coupling requires high temperatures (140–160 °C), chiral induction is high. This regiodivergent reaction, when carried out with enantiopure starting materials, can lead to single structurally different enantiopure products, depending on the catalyst chirality. The C?H activation at a tertiary center was realized only in the case of a cyclopropyl group. No C?H activation takes place alpha to a tertiary center. A detailed DFT study is included and analyses of methyl versus methylene versus methine C?H activation is used to rationalize experimentally observed regio‐ and enantioselectivities. 相似文献
4.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(32):9669-9673
A catalytic, versatile and atom‐economical C−H functionalization process that provides a wide variety of cyclic systems featuring methyl‐substituted quaternary stereocenters is described. The method relies on the use of a cationic IrI–bisphosphine catalyst, which promotes a carboxamide‐assisted activation of an olefinic C(sp2)−H bond followed by exo‐cyclization to a tethered 1,1‐disubstituted alkene. The extension of the method to aromatic and heteroaromatic C−H bonds, as well as developments on an enantioselective variant, are also described. 相似文献
5.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(13):3684-3688
We have developed a method for palladium‐catalyzed, pyrazole‐directed sp3 C−H bond arylation by aryl iodides. The reaction employs a Pd(OAc)2 catalyst at 5–10 mol % loading and silver(I) oxide as a halide‐removal agent, and it proceeds in acetic acid or acetic acid/hexafluoroisopropanol solvent. Ozonolysis of the pyrazole moiety affords pharmaceutically important β‐phenethylamines. 相似文献
6.
Masood Parvez Shaun T. Mesher Peter D. Clark 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(5):574-576
The structure of 2,5‐bis(methylthio)‐1,4‐benzoquinone, C8H8O2S2, is composed of an essentially planar centrosymmetric benzoquinone substituted with two methylthio groups. The important bond distances are S—Csp3 1.788 (2) and S—Csp2 1.724 (2) Å, and the two Csp2—Csp2 distances are 1.447 (3) and 1.504 (3) Å, which differ significantly. There are short S?S interactions of 3.430 (1) Å and Csp2—H?O‐type contacts forming a dimeric motif with graph set R22(8). The structure of 2‐methyl‐3‐(methylsulfonyl)benzo[b]thiophene, C10H10O2S2, is composed of an essentially planar benzothiophene moiety substituted with methyl and methylsulfonyl groups. The mean values of the important bond distances are endocyclic S—Csp2 1.734 (3), S=O 1.434 (4) and C—Caromatic 1.389 (10) Å. The exocyclic S—Csp2 and S—Csp3 distances are 1.759 (4) and 1.763 (5) Å, respectively. 相似文献
7.
Bottom‐up Construction of π‐Extended Arenes by a Palladium‐Catalyzed Annulative Dimerization of o‐Iodobiaryl Compounds
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Chendan Zhu Di Wang Dingyi Wang Yue Zhao Prof. Dr. Wei‐Yin Sun Prof. Dr. Zhuangzhi Shi 《Angewandte Chemie (International ed. in English)》2018,57(29):8848-8853
A straightforward method was developed for construction of aromatic compounds with a triphenylene core. The method involves Pd‐catalyzed annulative dimerization of o‐iodobiaryl compounds by double C?I and C?H bond cleavage steps. Simple reaction conditions are needed, requiring neither a ligand nor an oxidant, and the reaction tolerates a wide range of coupling partners without compromising efficiency or scalability. Significantly, the tetrachloro‐substituted synthon, 1,6,11‐trichloro‐4‐(4‐chlorophenyl)triphenylene, can be generated and used to prepare a series of fully fused, small graphene nanoribbons by a late‐stage arylation with arylboronic acids and a subsequent Scholl reaction. The synthetic strategy enables bottom‐up access to extended π‐systems in a controlled manner. 相似文献
8.
Jianbo Zhang Hoimin Jung Dongwook Kim Sehoon Park Sukbok Chang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(22):7439-7443
Described herein is an unprecedented access to BN‐polyaromatic compounds from 1,1′‐biphenylamines by sequential borane‐mediated C(sp2)?H borylation and intramolecular N‐demethylation. The conveniently in situ generated Piers’ borane from a borinic acid reacts with a series of N,N‐dimethyl‐1,1′‐biphenyl‐2‐amines in the presence of PhSiH3 to afford six‐membered amine‐borane adducts bearing a C(sp2)?B bond at the C2′‐position. These species undergo an intramolecular N‐demethylation with a B(C6F5)3 catalyst to provide BN‐isosteres of polyaromatics. According to computational studies, a stepwise ionic pathway is suggested. Photophysical characters of the resultant BN‐heteroarenes shown them to be distinctive from those of all‐carbon analogues. 相似文献
9.
Steric Effect of Carboxylate Ligands on Pd‐Catalyzed Intramolecular C(sp2)–H and C(sp3)–H Arylation Reactions
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Yutaka Tanji Naoya Mitsutake Prof. Dr. Tetsuaki Fujihara Prof. Dr. Yasushi Tsuji 《Angewandte Chemie (International ed. in English)》2018,57(32):10314-10317
A bulky carboxylic acid bearing three cyclohexylmethyl substituents at the α‐position, namely, tri(cyclohexylmethyl)acetic acid, is demonstrated to act as an efficient ligand source in Pd‐catalyzed intramolecular C(sp2)?H and C(sp3)?H arylation reactions. The reactions proceed smoothly under mild reaction conditions, even at room temperature due to the steric bulk of the carboxylate ligands, which accelerates the rate‐determining C?H bond activation step in the catalytic cycle. 相似文献
10.
Radical Cation Salt‐initiated Aerobic C−H Phosphorylation of N‐Benzylanilines: Synthesis of α‐Aminophosphonates
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Prof. Xiaodong Jia Xiaofei Liu Prof. Yu Yuan Pengfei Li Wentao Hou Kaixuan He 《化学:亚洲杂志》2018,13(15):1911-1914
A radical cation salt‐initiated phosphorylation of N‐benzylanilines was realized through an aerobic oxidation of the sp3 C?H bond, providing a series of α‐aminophosphonates in high yields. An investigation of the reaction scope revealed that this mild catalyst system is superior in good functional group tolerance and high reaction efficiency. The mechanistic study implied that the cleavage of the sp3 C?H bond was involved in the rate‐determining step. 相似文献
11.
3(2H)‐Furanones are efficiently generated from 3‐alkynyl oxireno[2,3‐b]chromenones by an Au/DDQ‐catalyzed domino reaction through a pathway composed of cyclization, C? C cleavage, nucleophilic addition, oxidation, and nucleophilic addition. It was found that stoichiometric AuCl3 or catalytic Au with stoichiometric DDQ can oxidize the benzylic sp3 C? H bond to facilitate nucleophilic addition. 相似文献
12.
Palladium‐Catalyzed γ‐C(sp3)−H Arylation of Thiols by a Detachable Protecting/Directing Group
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Likun Jin Jianchun Wang Prof. Dr. Guangbin Dong 《Angewandte Chemie (International ed. in English)》2018,57(38):12352-12355
Reported herein is a palladium‐catalyzed, directed γ‐C(sp3)?H arylation of protected thiols. The key is to utilize Michael acceptors as a dual reagent to install a protecting/directing group on thiols by a thiol‐Michael click reaction, and remove it later under basic conditions. The C?H arylation proceeds with high functional‐group tolerance and the deprotected thiols can be further transformed into other sulfur‐containing compounds. This unique mode of activation could open the door for site‐selective functionalization of thiols or other sulfur‐containing compounds at unactivated positions. 相似文献
13.
An Alternative to the Classical α‐Arylation: The Transfer of an Intact 2‐Iodoaryl from ArI(O2CCF3)2
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Dr. Zhiyu Jia Dr. Erik Gálvez Prof. Dr. Rosa María Sebastián Prof. Dr. Roser Pleixats Dr. Ángel Álvarez‐Larena Dr. Eddy Martin Prof. Dr. Adelina Vallribera Dr. Alexandr Shafir 《Angewandte Chemie (International ed. in English)》2014,53(42):11298-11301
The α‐arylation of carbonyl compounds is generally accomplished under basic conditions, both under metal catalysis and via aryl transfer from the diaryl λ3‐iodanes. Here, we describe an alternative metal‐free α‐arylation using ArI(O2CCF3)2 as the source of a 2‐iodoaryl group. The reaction is applicable to activated ketones, such as α‐cyanoketones, and works with substituted aryliodanes. This formal C? H functionalization reaction is thought to proceed through a [3,3] rearrangement of an iodonium enolate. The final α‐(2‐iodoaryl)ketones are versatile synthetic building blocks. 相似文献
14.
《化学:亚洲杂志》2017,12(7):734-743
A transition‐metal (TM)‐free and halogen‐free NaOt Bu‐mediated oxidative cross‐coupling between the sp3 C−H bond of oxindoles and sp2 C−H bond of nitroarenes has been developed to access 3‐aryl substituted and 3,3‐aryldisubstituted oxindoles in DMSO at room temperature in a short time. Interestingly, the sp3 C−H bond of oxindoles could also react with styrene under TM‐free conditions for the practical synthesis of quaternary 3,3‐disubstituted oxindoles. The synthesized 3‐oxindoles have also been further transformed into advanced heterocycles, that is, benzofuroindoles, indoloindoles, and substituted indoles. Mechanistic experiments of the reaction suggests the formation of an anion intermediate from the sp3 C−H bond of oxindole by tert ‐butoxide base in DMSO. The addition of nitrobenzene to the in‐situ generated carbanion leads to the 3‐(nitrophenyl)oxindolyl carbanion in DMSO which is subsequently oxidized to 3‐(nitro‐aryl) oxindole by DMSO. 相似文献
15.
Hai‐Xu Wang Yann Richard Qingyun Wan Cong‐Ying Zhou Chi‐Ming Che 《Angewandte Chemie (International ed. in English)》2020,59(5):1845-1850
Described herein is an IrIII/porphyrin‐catalyzed intermolecular C(sp3)?H insertion reaction of a quinoid carbene (QC). The reaction was designed by harnessing the hydrogen‐atom transfer (HAT) reactivity of a metal‐QC species with aliphatic substrates followed by a radical rebound process to afford C?H arylation products. This methodology is efficient for the arylation of activated hydrocarbons such as 1,4‐cyclohexadienes (down to 40 min reaction time, up to 99 % yield, up to 1.0 g scale). It features unique regioselectivity, which is mainly governed by steric effects, as the insertion into primary C?H bonds is favored over secondary and/or tertiary C?H bonds in the substituted cyclohexene substrates. Mechanistic studies revealed a radical mechanism for the reaction. 相似文献
16.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(6):1528-1531
Herein we report acid‐directed β‐C(sp3)‐H arylation of α‐amino acids enabled by pyridine‐type ligands. This reaction does not require the installation of an exogenous directing group, is scalable, and enables the preparation of Fmoc‐protected unnatural amino acids in three steps. The pyridine‐type ligands are crucial for the development of this new C(sp3)‐H arylation. 相似文献
17.
Practical Synthesis of anti‐β‐Hydroxy‐α‐Amino Acids by PdII‐Catalyzed Sequential C(sp3)H Functionalization
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Kai Chen Shuo‐Qing Zhang Huai‐Zhi Jiang Jing‐Wen Xu Prof. Dr. Bing‐Feng Shi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(8):3264-3270
An improved and practical procedure for the stereoselective synthesis of anti‐β‐hydroxy‐α‐amino acids (anti‐βhAAs), by palladium‐catalyzed sequential C(sp3)?H functionalization directed by 8‐aminoquinoline auxiliary, is described. followed by a previously established monoarylation and/or alkylation of the β‐methyl C(sp3)?H of alanine derivative, β‐acetoxylation of both alkylic and benzylic methylene C(sp3)?H bonds affords various anti‐β‐hydroxy‐α‐amino acid derivatives. As an example, the synthesis of β‐mercapto‐α‐amino acids, which are highly important to the extension of native chemical ligation chemistry beyond cysteine, is described. The synthetic potential of this protocol is further demonstrated by the synthesis of diverse β‐branched α‐amino acids. The observed diastereoselectivities are strongly influenced by electronic effects of aromatic AAs and steric effects of the linear side‐chain AAs, which could be explained by the competition of intramolecular C?OAc bond reductive elimination from PdIV intermediates vs. intermolecular attack by an external nucleophile (AcO?) in an SN2‐type process. 相似文献
18.
Homolytic,Heterolytic, Mesolytic ‐ As You Like It: Steering the Cleavage of a HC(sp3)−C(sp3)H Bond in Bis(1H‐2,1‐benzazaborole) Derivatives
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Martin Hejda Prof. Antonín Lyčka Dr. Tomáš Mikysek Dr. Roman Jambor Prof. Aleš Růžička Dr. Jaromír Vinklárek Dr. Claudia Wilfer Dr. Alexander Hoffmann Prof. Sonja Herres‐Pawlis Dr. Libor Dostál 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(43):15340-15349
A set of (3,3′)‐bis(1‐Ph‐2‐R‐1H‐2,1‐benzazaborole) compounds, in which R=tBu (Bab‐tBu)2 , R=Dipp (Bab‐Dipp)2 or R=tBu and Dipp (Bab‐Dipp)(Bab‐tBu) , was synthesized and fully characterized using 1H, 11B, 13C, and 15N NMR spectroscopy as well as single‐crystal X‐ray diffraction analysis. The central HC(sp3)?C(sp3)H bond with restricted rotation at the junction of both 1H‐2,1‐benzazaborole rings displayed an intriguing reactivity. It was demonstrated that this bond is easily mesolytically cleaved using alkali metals to form the respective aromatic 1Ph‐2R‐1H‐2,1‐benzazaborolyl anions M+(THF) n (Bab‐tBu)? (M=Li, Na, K) and K+(THF) n (Bab‐Dipp)? . Furthermore, the central HC(sp3)?C(sp3)H bond of bis(1H‐2,1‐benzazaborole)s is also homolytically cleaved either by heating or photochemical means, giving corresponding 1Ph‐2R‐1H‐2,1‐benzazaborolyl radicals (Bab‐tBu). and (Bab‐Dipp)., which rapidly self‐terminate. Nevertheless, their formation was unambiguously established by NMR analysis of the reaction mixtures containing products of the self‐termination of the radicals after heating or irradiation. (Bab‐Dipp). radical was also characterized using EPR spectroscopy. Importantly, it turned out that the essentially non‐polarized HC(sp3)?C(sp3)H bond in (Bab‐tBu)2 is also cleaved heterolytically with 2 equiv of MeLi, giving the mixture of Li+(SOL) n (Bab‐tBu)? (SOL=THF or Et2O) and lithium methyl‐substituted borate complex Li+(SOL) n (Bab‐tBu‐Me)? in a diastereoselective fashion. 相似文献
19.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(43):13509-13513
The first oxidative C(sp3)−H/C(sp3)−H cross‐dehydrogenative coupling (CDC) reaction promoted by an internal oxidant is reported. This copper‐catalyzed CDC reaction of oxime acetates and trifluoromethyl ketones provides a simple and efficient approach towards 2‐trifluoromethyldihydropyrrol‐2‐ol derivatives in a highly diastereoselective manner by cascade C(sp3)−C(sp3) bond formation and cyclization. These products were further transformed into various significant and useful trifluoromethylated heterocyclic compounds, such as trifluoromethylated furan, thiophene, pyrrole, dihydropyridazine, and pyridazine derivatives. A trifluoromethylated analogue of an Aβ42 lowering agent was also synthesized smoothly. Preliminary mechanistic studies indicated that this reaction involves a copper(I)/copper(III) catalytic cycle with the oxime acetate acting as an internal oxidant. 相似文献
20.
Jeffrey A. Boerth Joshua R. Hummel Prof. Dr. Jonathan A. Ellman 《Angewandte Chemie (International ed. in English)》2016,55(41):12650-12654
A highly stereoselective three‐component C(sp2)?H bond addition across alkene and polarized π‐bonds is reported for which CoIII catalysis was shown to be much more effective than RhIII. The reaction proceeds at ambient temperature with both aryl and alkyl enones employed as efficient coupling partners. Moreover, the reaction exhibits extremely broad scope with respect to the aldehyde input; electron rich and poor aromatic, alkenyl, and branched and unbranched alkyl aldehydes all couple in good yield and with high diastereoselectivity. Multiple directing groups participate in this transformation, including pyrazole, pyridine, and imine functional groups. Both aromatic and alkenyl C(sp2)?H bonds undergo the three‐component addition cascade, and the alkenyl addition product can readily be converted into diastereomerically pure five‐membered lactones. Additionally, the first asymmetric reactions with CoIII‐catalyzed C?H functionalization are demonstrated with three‐component C?H bond addition cascades employing N‐tert‐butanesulfinyl imines. These examples represent the first transition metal catalyzed C?H bond additions to N‐tert‐butanesulfinyl imines, which are versatile and extensively used intermediates for the asymmetric synthesis of amines. 相似文献