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Palladium(II)‐Catalyzed Enantioselective Arylation of Unbiased Methylene C(sp3)−H Bonds Enabled by a 2‐Pyridinylisopropyl Auxiliary and Chiral Phosphoric Acids 下载免费PDF全文
Sheng‐Yi Yan Ye‐Qiang Han Qi‐Jun Yao Xing‐Liang Nie Lei Liu Prof. Dr. Bing‐Feng Shi 《Angewandte Chemie (International ed. in English)》2018,57(29):9093-9097
Enantioselective functionalizations of unbiased methylene C(sp3)?H bonds of linear systems by metal insertion are intrinsically challenging and remain a largely unsolved problem. Herein, we report a palladium(II)‐catalyzed enantioselective arylation of unbiased methylene β‐C(sp3)?H bonds enabled by the combination of a strongly coordinating bidentate PIP auxiliary with a monodentate chiral phosphoric acid (CPA). The synergistic effect between the PIP auxiliary and the non‐C2‐symmetric CPA is crucial for effective stereocontrol. A broad range of aliphatic carboxylic acids and aryl bromides can be used, providing β‐arylated aliphatic carboxylic acid derivatives in high yields (up to 96 %) with good enantioselectivities (up to 95:5 e.r.). Notably, this reaction also represents the first palladium(II)‐catalyzed enantioselective C?H activation with less reactive and cost‐effective aryl bromides as the arylating reagents. Mechanistic studies suggest that a single CPA is involved in the stereodetermining C?H palladation step. 相似文献
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Synthesis of Strained γ‐Lactams by Palladium(0)‐Catalyzed C(sp3)−H Alkenylation and Application to Alkaloid Synthesis 下载免费PDF全文
Dr. Philipp M. Holstein David Dailler Julien Vantourout Janah Shaya Dr. Anthony Millet Prof. Dr. Olivier Baudoin 《Angewandte Chemie (International ed. in English)》2016,55(8):2805-2809
A variety of strained α‐alkylidene‐γ‐lactams were synthesized by palladium(0)‐catalyzed intramolecular C(sp3)?H alkenylation from easily accessible acyclic and monocyclic bromoalkene precursors. These lactams are valuable intermediates for accessing various classes of mono‐ and bicylic alkaloids containing a pyrrolidine ring, as illustrated with the synthesis of an advanced model of the marine natural product plakoridine A and of the indolizidine alkaloid δ‐coniceine. 相似文献
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Enantioselective Access to 1H‐Isoindoles with Quaternary Stereogenic Centers by Palladium(0)‐Catalyzed C−H Functionalization 下载免费PDF全文
Daria Grosheva Prof. Dr. Nicolai Cramer 《Angewandte Chemie (International ed. in English)》2018,57(41):13644-13647
A catalytic enantioselective method for the synthesis of chiral 1H‐isoindoles bearing quaternary stereogenic centers is reported. Powered by readily accessible phosphordiamidite ligands, the presented palladium(0)‐catalyzed C?H functionalization uses trifluoroacetimidoyl chlorides as electrophilic components. It delivers previously inaccessible perfluoroalkylated 1H‐isoindoles in high yields and enantioselectivities. The subsequent diastereoselective addition of nucleophiles provides access to densely substituted and sterically hindered isoindolines. 相似文献
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Dr. Ryo Murakami Kentaro Sano Dr. Tomohiro Iwai Prof. Dr. Tohru Taniguchi Prof. Dr. Kenji Monde Prof. Dr. Masaya Sawamura 《Angewandte Chemie (International ed. in English)》2018,57(30):9465-9469
The palladium‐catalyzed asymmetric side‐chain C(α)‐allylation of 2‐alkylpyridines, without using an external base, was developed. The high linear selectivities and enantioselectivities were achieved using new chiral diamidophosphite monodentate ligands. Given that the reaction conditions do not require an external base, this catalyst system enabled chemoselective C(α)‐allylation of 2‐alkylpyridines containing α‐carbonyl C?H bonds, which are more acidic than α‐pyridyl C?H bonds. 相似文献
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Satoshi Suetsugu Nobusuke Muto Misa Horinouchi Dr. Chihiro Tsukano Prof. Dr. Yoshiji Takemoto 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(24):8059-8062
A new method has been developed for the synthesis of tetrahydro‐2H‐fluorenes based on a Pd(0)‐catalyzed benzylic C(sp3)?H functionalization. Importantly, the success of the cyclization step was dependent on there being substituents at the two positions ortho to the benzylic group to avoid an undesired C(sp2)?H functionalization. This method was subsequently used to prepare the right‐hand fragment of the hexacyclic triterpenoid benzohopanes, and therefore represents a powerful tool for the construction of the related compounds. 相似文献
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Ming Chen Feipeng Liu Prof.Dr. Guangbin Dong 《Angewandte Chemie (International ed. in English)》2018,57(14):3815-3819
A direct and catalytic method is reported here for β‐arylation of N‐protected lactams with simple aryl iodides. The transformation is enabled by merging soft enolization of lactams, palladium‐catalyzed desaturation, Ar?X bond activation, and aryl conjugate addition. The reaction is operated under mild reaction conditions, is scalable, and is chemoselective. Application of this method to concise syntheses of pharmaceutically relevant compounds is demonstrated. 相似文献
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Palladium‐Catalyzed γ‐C(sp3)−H Arylation of Thiols by a Detachable Protecting/Directing Group 下载免费PDF全文
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
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Domino Pd0‐Catalyzed C(sp3)–H Arylation/Electrocyclic Reactions via Benzazetidine Intermediates 下载免费PDF全文
Ronan Rocaboy Dr. David Dailler Florian Zellweger Dr. Markus Neuburger Dr. Christophe Salomé Dr. Eric Clot Prof. Dr. Olivier Baudoin 《Angewandte Chemie (International ed. in English)》2018,57(37):12131-12135
The Pd0‐catalyzed C(sp3)‐H arylation of 2‐bromo‐N‐methylanilides leads to unstable benzazetidine intermediates that rearrange to benzoxazines through 4π electrocyclic ring‐opening and 6π electrocyclization. The introduction of a bulky, non‐activatable amide group on the nitrogen atom was key to favor the challenging reductive elimination step and disfavor undesired reaction pathways. 相似文献
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Steric Effect of Carboxylate Ligands on Pd‐Catalyzed Intramolecular C(sp2)–H and C(sp3)–H Arylation Reactions 下载免费PDF全文
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
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Enantioselective C−H Olefination of α‐Hydroxy and α‐Amino Phenylacetic Acids by Kinetic Resolution 下载免费PDF全文
Dr. Kai‐Jiong Xiao Ling Chu Prof. Dr. Jin‐Quan Yu 《Angewandte Chemie (International ed. in English)》2016,55(8):2856-2860
Significant progress has been made in the past decade regarding the development of enantioselective C?H activation reactions by desymmetrization. However, the requirement for the presence of two chemically identical prochiral C?H bonds represents an inherent limitation in scope. Reported is the first example of kinetic resolution by a palladium(II)‐catalyzed enantioselective C?H activation and C?C bond formation, thus significantly expanding the scope of enantioselective C?H activation reactions. 相似文献
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Mechanism of Nickel(II)‐Catalyzed Oxidative C(sp2)−H/C(sp3)−H Coupling of Benzamides and Toluene Derivatives 下载免费PDF全文
The Ni‐catalyzed C(sp2)?H/C(sp3)?H coupling of benzamides with toluene derivatives was recently successfully achieved with mild oxidant iC3F7I. Herein, we employ density functional theory (DFT) methods to resolve the mechanistic controversies. Two previously proposed mechanisms are excluded, and our proposed mechanism involving iodine‐atom transfer (IAT) between iC3F7I and the NiII intermediate was found to be more feasible. With this mechanism, the presence of a carbon radical is consistent with the experimental observation that (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO) completely quenches the reaction. Meanwhile, the hydrogen‐atom abstraction of toluene is irreversible and the activation of the C(sp2)?H bond of benzamides is reversible. Both of these conclusions are in good agreement with Chatani's deuterium‐labeling experiments. 相似文献
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Hua‐Jie Jiang Xiu‐Mei Zhong Zi‐Ye Liu Rui‐Long Geng Yang‐Yang Li Yun‐Dong Wu Xinhao Zhang Liu‐Zhu Gong 《Angewandte Chemie (International ed. in English)》2020,59(31):12774-12778
A hybrid palladium catalyst assembled from a chiral phosphoric acid (CPA) and thioamide enables a highly efficient and enantioselective β‐C(sp3)?H functionalization of thioamides (up to 99 % yield, 97 % ee). A kinetic resolution of unsymmetrical thioamides by intermolecular C(sp3)?H arylation can be achieved with high s‐factors. Mechanistic investigations have revealed that stereocontrol is achieved by embedding the substrate in a robust chiral cavity defined by the bulky CPA and a neutral thioamide ligand. 相似文献
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Julia Pedroni Michele Boghi Dr. Tanguy Saget Prof. Dr. Nicolai Cramer 《Angewandte Chemie (International ed. in English)》2014,53(34):9064-9067
β‐Lactams are very important structural motifs because of their broad biological activities as well as their propensity to engage in ring‐opening reactions. Transition‐metal‐catalyzed C? H functionalizations have emerged as strategy enabling yet uncommon highly efficient disconnections. In contrast to the significant progress of Pd0‐catalyzed C? H functionalization for aryl–aryl couplings, related reactions involving the formation of saturated C(sp3)? C(sp3) bonds are elusive. Reported here is an asymmetric C? H functionalization approach to β‐lactams using readily accessible chloroacetamide substrates. Important aspects of this transformation are challenging C(sp3)? C(sp3) and strain‐building reductive eliminations to for the four‐membered ring. In general, the β‐lactams are formed in excellent yields and enantioselectivities using a bulky taddol phosphoramidite ligand in combination with adamantyl carboxylic acid as cocatalyst. 相似文献
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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
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An Enantioselective Bidentate Auxiliary Directed Palladium‐Catalyzed Benzylic C−H Arylation of Amines Using a BINOL Phosphate Ligand 下载免费PDF全文
Hao Wang Hua‐Rong Tong Prof. Dr. Gang He Prof. Dr. Gong Chen 《Angewandte Chemie (International ed. in English)》2016,55(49):15387-15391
A new enantioselective palladium(II)‐catalyzed benzylic C?H arylation reaction of amines is enabled by the bidentate picolinamide (PA) directing group. This reaction provides the first example of enantioselective benzylic γ‐C?H arylations of alkyl amines, and proceeds with up to 97 % ee. The 2,2′‐dihydroxy‐1,1′‐binaphthyl (BINOL) phosphoric acid ligand, Cs2CO3, and solvent‐free conditions are essential for high enantioselectivity. Mechanistic studies suggest that multiple BINOL ligands are involved in the stereodetermining C?H palladation step. 相似文献
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In recent years, transition‐metal‐catalyzed C?H activation has become a key strategy in the field of organic synthesis. Rhodium complexes are widely used as catalysts in a variety of C?H functionalization reactions because of their high reactivity and selectivity. The availability of a number of rhodium complexes in various oxidation states enables diverse reaction patterns to be obtained. Regioselectivity, an important issue in C?H activation chemistry, can be accomplished by using a directing group to assist the reaction. However, to obtain the target functionalized compounds, it is also necessary to use a directing group that can be easily removed. A wide range of directed C?H functionalization reactions catalyzed by rhodium complexes have been reported to date. In this Review, we discuss Rh‐catalyzed C?H functionalization reactions that are aided by the use of a removable directing group such as phenol, amine, aldehyde, ketones, ester, acid, sulfonic acid, and N‐heteroaromatic derivatives. 相似文献
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Yan Lin Wei‐Yang Ma Zheng Xu Zhan‐Jiang Zheng Jian Cao Ke‐Fang Yang Yu‐Ming Cui Li‐Wen Xu 《化学:亚洲杂志》2019,14(12):2082-2085
A palladium‐catalyzed chelation‐assisted enantioselective C?H olefination of symmetrically diaryl‐substituted tetraorganosilicon derivatives was developed, enabling the generation of nitrogen‐containing silicon‐stereogenic tetraorganosilicon compounds with modest to good yields and good to excellent enantioselectivities (up to 95.5:4.5 e.r.). The Thorpe–Ingold effect exerted by the substituents on silicon was observed to have a profound influence on formation of olefinated products which were further converted into other relevant chiral organosilanes without the loss of enantiomeric purity, thus demonstrating the synthetic utility of the developed enantioselective olefination. 相似文献
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Cobalt‐Catalyzed Tandem C−H Activation/C−C Cleavage/C−H Cyclization of Aromatic Amides with Alkylidenecyclopropanes 下载免费PDF全文
Dr. Mingliang Li Prof. Dr. Fuk Yee Kwong 《Angewandte Chemie (International ed. in English)》2018,57(22):6512-6516
A cobalt‐catalyzed chelation‐assisted tandem C?H activation/C?C cleavage/C?H cyclization of aromatic amides with alkylidenecyclopropanes is reported. This process allows the sequential formation of two C?C bonds, which is in sharp contrast to previous reports on using rhodium catalysts for the formation of C?N bonds. Here the inexpensive catalyst system exhibits good functional‐group compatibility and relatively broad substrate scope. The desired products can be easily transformed into polycyclic lactones with m‐CPBA. Mechanistic studies revealed that the tandem reaction proceeds through a C?H cobaltation, β‐carbon elimination, and intramolecular C?H cobaltation sequence. 相似文献