共查询到20条相似文献,搜索用时 15 毫秒
1.
Kiron Kumar Ghosh Alexander Uttry Arup Mondal Francesca Ghiringhelli Philipp Wedi Manuel van Gemmeren 《Angewandte Chemie (International ed. in English)》2020,59(31):12848-12852
We report the ligand‐enabled C?H activation/olefination of free carboxylic acids in the γ‐position. Through an intramolecular Michael addition, δ‐lactones are obtained as products. Two distinct ligand classes are identified that enable the challenging palladium‐catalyzed activation of free carboxylic acids in the γ‐position. The developed protocol features a wide range of acid substrates and olefin reaction partners and is shown to be applicable on a preparatively useful scale. Insights into the underlying reaction mechanism obtained through kinetic studies are reported. 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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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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Daniel Bafaluy Zoritsa Georgieva Kilian Muiz 《Angewandte Chemie (International ed. in English)》2020,59(34):14241-14245
Iodine catalysis was developed for aliphatic fluorination through light‐promoted homolytic C?H bond cleavage. The intermediary formation of amidyl radicals enables selective C?H functionalization via carbon‐centered radicals. For the subsequent C?F bond formation, previous methods have typically been limited by a requirement for electrophilic fluorine reagents. We here demonstrate that the intermediary instalment of a carbon–iodine bond sets the stage for an umpolung, thereby establishing an unprecedented nucleophilic fluorination pathway. 相似文献
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Qiang Yue, Xu Yang, Meng‐Xue Jiang, Bing‐Feng Shi, Tao Zhou, Yi Ding and Ye‐Qiang Han (from left to right). Mr. Tao Zhou is currently a postdoctoral fellow in the group of Prof. Bing‐Feng Shi in Zhejiang University. Mr. Ye‐Qiang Han is currently a fourth‐year PhD student in the group of Prof. Bing‐Feng Shi in Zhejiang University. 相似文献
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α‐Aminoxy‐Acid‐Auxiliary‐Enabled Intermolecular Radical γ‐C(sp3)−H Functionalization of Ketones 下载免费PDF全文
Dr. Heng Jiang Prof. Dr. Armido Studer 《Angewandte Chemie (International ed. in English)》2018,57(6):1692-1696
A method for site‐specific intermolecular γ‐C(sp3)?H functionalization of ketones has been developed using an α‐aminoxy acid auxiliary applying photoredox catalysis. Regioselective activation of an inert C?H bond is achieved by 1,5‐hydrogen atom abstraction by an oxidatively generated iminyl radical. Tertiary and secondary C‐radicals thus formed at the γ‐position of the imine functionality undergo radical conjugate addition to various Michael acceptors to provide, after reduction and imine hydrolysis, the corresponding γ‐functionalized ketones. 相似文献
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Jian Wen Ben Dong Jinjun Zhu Yue Zhao Zhuangzhi Shi 《Angewandte Chemie (International ed. in English)》2020,59(27):10909-10912
The first aromatic C?H silylation between arylphosphines and hydrosilanes enabled by a ruthenium complex has been developed. The excellent ortho‐selectivity results from a four‐membered metallacyclic intermediate involving phosphorus chelation. The developed system can be extended to the benzylic C?H silylation of arylphosphines. Diverse silylated arylphosphines are produced, exhibiting broad functional group compatibility. Further functionalization of the products under mild conditions renders the formed compounds useful building blocks. 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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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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Quan Gou Yu‐Wen Yang Zi‐Ning Liu Prof. Jun Qin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(45):16057-16061
The first example of intermolecular amination of unactivated C(sp3)?H bonds by cyclic alkylamines mediated by Cu(OAc)2/O2 is reported. This method avoids the use of benzoyloxyamines as the aminating reagent, which are normally prepared from alkylamines in extra steps. A variety of unnatural β2, 2‐amino acid analogues are synthesized by this simple and efficient procedure. This approach offers a solution to the previous unmet challenge of C(sp3)?H/N?H activation for the formation of C(sp3)?N bonds. 相似文献
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Ming Gong Prof. Dr. Jing‐Mei Huang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(40):14293-14296
A mild method for the direct C?H/N?H coupling between γ‐lactams and anilines through electrochemical oxidation has been developed. The protocol proceeded smoothly without metal catalysts at room temperature to afford γ‐substituted γ‐lactams in good yields. It has been revealed that the quasi‐divided cell which provided high current density on the anode was crucial for this reaction. 相似文献
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Alexandra E. Bosnidou Kilian Muiz 《Angewandte Chemie (International ed. in English)》2019,58(22):7485-7489
The direct amination of aliphatic C?H bonds has remained one of the most tantalizing transformations in organic chemistry. Herein, we report on a unique catalyst system, which enables the elusive intermolecular C(sp3)?H amination. This practical synthetic strategy provides access to aminated building blocks and fosters innovative multiple C?H amination within a new approach to aminated heterocycles. The synthetic utility is demonstrated by the synthesis of four relevant pharmaceuticals. 相似文献
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Yi Ding Ye‐Qiang Han Le‐Song Wu Tao Zhou Qi‐Jun Yao Ya‐Lan Feng Ya Li Ke‐Xin Kong Bing‐Feng Shi 《Angewandte Chemie (International ed. in English)》2020,59(33):14060-14064
Herein, we describe an unprecedented cascade reaction to β‐stereogenic γ‐lactams involving Pd(II)‐catalyzed enantioselective aliphatic methylene C(sp3)?H alkenylation–aza‐Wacker cyclization through syn‐aminopalladation. Readily available 3,3′‐substituted BINOLs are used as chiral ligands, providing the corresponding γ‐lactams with broad scope and high enantioselectivities (up to 98 % ee). 相似文献
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Catalytic Asymmetric Intramolecular Homologation of Ketones with α‐Diazoesters: Synthesis of Cyclic α‐Aryl/Alkyl β‐Ketoesters 下载免费PDF全文
Dr. Wei Li Fei Tan Xiaoyu Hao Gang Wang Yu Tang Prof. Dr. Xiaohua Liu Dr. Lili Lin Prof. Dr. Xiaoming Feng 《Angewandte Chemie (International ed. in English)》2015,54(5):1608-1611
A catalytic asymmetric intramolecular homologation of simple ketones with α‐diazoesters was firstly accomplished with a chiral N,N′‐dioxide–Sc(OTf)3 complex. This method provides an efficient access to chiral cyclic α‐aryl/alkyl β‐ketoesters containing an all‐carbon quaternary stereocenter. Under mild conditions, a variety of aryl‐ and alkyl‐substituted ketone groups reacted with α‐diazoester groups smoothly through an intramolecular addition/rearrangement process, producing the β‐ketoesters in high yield and enantiomeric excess. 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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Guoqin Xia Zhe Zhuang Luo‐Yan Liu Stuart L. Schreiber Bruno Melillo Jin‐Quan Yu 《Angewandte Chemie (International ed. in English)》2020,59(20):7783-7787
Despite recent advances, reactivity and site‐selectivity remain significant obstacles for the practical application of C(sp3)?H bond functionalization methods. Here, we describe a system that combines a salicylic‐aldehyde‐derived L,X‐type directing group with an electron‐deficient 2‐pyridone ligand to enable the β‐methylene C(sp3)?H arylation of aliphatic alcohols, which has not been possible previously. Notably, this protocol is compatible with heterocycles embedded in both alcohol substrates and aryl coupling partners. A site‐ and stereo‐specific annulation of dihydrocholesterol and the synthesis of a key intermediate of englitazone illustrate the practicality of this method. 相似文献
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Synthesis of β‐Haloketones by β‐Addition Reactions of α,β‐Unsaturated Ketones with BX3 (X = Br,Cl) as Halide Source 下载免费PDF全文
A series of β‐bromoketones and β‐chloroketones were synthesized by the addition reactions of α,β‐unsaturated ketones under BX3 (X = Br, Cl) and ethylene glycol reaction system. The α,β‐unsaturated ester also was successfully converted to its corresponding β‐bromoester under the reaction condition. 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