共查询到20条相似文献,搜索用时 15 毫秒
1.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(32):9543-9547
C−H/C−C functionalizations with methylenecyclopropanes (MCPs) were accomplished with a versatile base‐metal catalyst. A robust manganese(I) complex enabled the expedient annulation of MCPs by synthetically meaningful ketimines to deliver, upon one‐pot hydroarylation, densely substituted polycylic anilines in a step‐economical fashion. Mechanistic studies provided strong support for a facile organometallic C−H manganation, while typical cobalt, ruthenium, rhodium, and palladium catalysts were found completely ineffective. 相似文献
2.
N. Y. Phani Kumar Alexander Bechtoldt Keshav Raghuvanshi Lutz Ackermann 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(24):7043-7046
Ruthenium(II) bis(carboxylate)s proved highly effective for two decarboxylative C−H alkenylation strategies. The decarboxylation proceeded efficiently at rather low temperatures. The unique versatility of the decarboxylative ruthenium(II) catalysis is reflected in the oxidative olefinations with alkenes as well as the redox‐neutral hydroarylations of alkynes. 相似文献
3.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(35):10514-10518
Selectivity control in hydroarylation‐based C−H alkylation has been dominated by steric interactions. A conceptually distinct strategy that exploits the programmed switch in the C−H activation mechanism by means of cobalt catalysis is presented, which sets the stage for convenient C−H alkylations with unactivated alkenes. Detailed mechanistic studies provide compelling evidence for a programmable switch in the C−H activation mechanism from a linear‐selective ligand‐to‐ligand hydrogen transfer to a branched‐selective base‐assisted internal electrophilic‐type substitution. 相似文献
4.
Jompol Thongpaen Romane Manguin Vincent Dorcet Thomas Vives Carine Duhayon Marc Mauduit Olivier Basl 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(43):15388-15392
An efficient visible light induced rhodium(I)‐catalyzed regioselective borylation of aromatic C?H bonds is reported. The photocatalytic system is based on a single NHC?RhI complex capable of both harvesting visible light and enabling the bond breaking/forming at room temperature. The chelating nature of the NHC‐carboxylate ligand was critical to ensure the stability of the RhI complex and to provide excellent photocatalytic activities. Experimental mechanistic studies evidenced a photooxidative ortho C?H bond addition upon irradiation with blue LEDs, leading to a cyclometalated RhIII‐hydride intermediate. 相似文献
5.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(4):1089-1092
Pyridine activation by inexpensive iron catalysts has great utility, but the steps through which iron species can break the strong (105–111 kcal mol−1) C−H bonds of pyridine substrates are unknown. In this work, we report the rapid room‐temperature cleavage of C−H bonds in pyridine, 4‐tert‐butylpyridine, and 2‐phenylpyridine by an iron(I) species, to give well‐characterized iron(II) products. In addition, 4‐dimethylaminopyridine (DMAP) undergoes room‐temperature C−N bond cleavage, which forms a dimethylamidoiron(II) complex and a pyridyl‐bridged tetrairon(II) square. These facile bond‐cleaving reactions are proposed to occur through intermediates having a two‐electron reduced pyridine that bridges two iron centers. Thus, the redox non‐innocence of the pyridine can play a key role in enabling high regioselectivity for difficult reactions. 相似文献
6.
Jiangliang Yin Jingsong You 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(1):308-312
Disclosed herein is the merging of C?H activation and radical chemistry, enabling rapid access to a structurally diverse family of fused carbohelicenes through the fusion of α‐acetylnaphthalenes with alkynes under oxidative conditions. This cascade process exhibits exquisite chemoselectivity and regioselectivity. The reaction pathway was analyzed by intermediate separations, control experiments, radical trapping, EPR, MALDI‐TOF‐MS, and ESI‐HRMS experiments, and shown to involve a C2?H activation/radical reaction/C8?H activation relay. 相似文献
7.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(46):14666-14670
We report a powerful strategy for activation of C−H bonds to produce polysulfonamides by an atom‐economical and green method using iridium‐catalyzed direct C−H amidation polymerization (DCAP). After screening various directing groups, additives, silver salts, concentrations, and temperatures to optimize DCAP, high‐molecular‐weight (up to 149 kDa) and defect‐free polysulfonamides were synthesized from various bis‐sulfonyl azides. Although these polymers do not have conventional fluorescent conjugated cores, they emit blue light with large Stokes shifts and high quantum yields upon photoexcitation owing to an excited‐state intramolecular proton‐transfer process. 相似文献
8.
9.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(33):10071-10075
Heteroarenes are important structural motif in functional molecules. A MnI‐catalyzed 1,2‐diheteroarylation of allenes via a C−H activation/Smiles rearrangement cascade is presented. The reaction occurred under additive‐free or even solvent‐free conditions, which allowed the creation of two C−C and one C−N bonds in a single operation. A series of structurally diverse bicyclic or tricyclic compounds bearing an exocyclic double bond were constructed in good to excellent efficiency. The decarboxylative ring‐opening of the products led to the facile synthesis of vicinal biheteroaryls. Synthetic applications were demonstrated and preliminary mechanistic studies were conducted. 相似文献
10.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(39):12120-12124
Palladium(II)‐catalyzed C−H carbonylation reactions of methylene C−H bonds in secondary aliphatic amines lead to the formation of trans ‐disubstituted β‐lactams in excellent yields and selectivities. The generality of the C−H carbonylation process is aided by the action of xantphos‐based ligands and is important in securing good yields for the β‐lactam products. 相似文献
11.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(1):370-373
Compounds with stereogenic phosphorus atoms are frequently used as ligands for transition‐metal as well as organocatalysts. A direct catalytic enantioselective method for the synthesis of P ‐chiral compounds from easily accessible diaryl phosphinamides is presented. The use of rhodium(III) complexes equipped with a suitable atropochiral cyclopentadienyl ligand is shown to enable an enantiodetermining C−H activation step. Upon trapping with alkynes, a broad variety of cyclic phosphinamides with a stereogenic phosphorus(V) atom are formed in high yields and enantioselectivities. Moreover, these can be reduced enantiospecifically to P ‐chiral phosphorus(III) compounds. 相似文献
12.
Ryosuke Yamada Nobuharu Iwasawa Jun Takaya 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(48):17411-17414
Rhodium complexes with an indium metalloligand were successfully synthesized by utilizing a pyridine‐tethered cyclopentadienyl ligand as a support for an In?Rh bond. The indium metalloligand dramatically changes the electronic and redox properties of the rhodium metal, thereby enabling catalysis of sp2C?H bond activation. 相似文献
13.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(50):16107-16111
A unified strategy for nickel(0)‐catalyzed C−H allylations, alkenylations, and dienylations has been realized through versatile hydroarylations of allenes with ample scope. Thus, an inexpensive nickel catalyst modified with a N ‐heterocyclic carbene ligand enabled the direct transformation of C−H bonds of biologically relevant imidazole and purine derivatives with full control of regio‐ and chemoselectivity. 相似文献
14.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(7):1903-1906
Despite recent progress in the catalytic transformation of inert phenol derivatives as alternatives to aryl halides and triflates, attempts at the cross‐coupling of inert phenol derivatives with the C−H bonds of arenes have met with limited success. Herein, we report the rhodium‐catalyzed cross‐coupling of aryl carbamates with arenes bearing a convertible directing group. The key to success is the use of an in situ generated rhodium bis(N‐heterocyclic carbene) species as the catalyst, which can promote activation of the inert C(sp2)−O bond in aryl carbamates. 相似文献
15.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(1):320-324
Despite the importance of stapled peptides for drug discovery, only few practical processes to prepare cross‐linked peptides have been described; thus the structural diversity of available staple motifs is currently limited. At the same time, C−H activation has emerged as an efficient approach to functionalize complex molecules. Although there are many reports on the C−H functionalization of amino acids, examples of post‐synthetic peptide C−H modification are rare and comprise almost only C(sp2)−H activation. Herein, we report the development of a palladium‐catalyzed late‐stage C(sp3)−H activation method for peptide stapling, affording an unprecedented hydrocarbon cross‐link. This method was first employed to prepare a library of stapled peptides in solution. The compatibility with various amino acids as well as the influence of the size (i ,i +3 and i ,i +4) and length of the staple were investigated. Finally, a simple solid‐phase procedure was also established. 相似文献
16.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(35):10666-10670
The development of new and practical 3‐pentoxythiocarbonyl auxiliaries for IrI‐catalyzed C−H alkylation of azacycles is described. This method allows for the α‐C−H alkylation of a variety of substituted pyrrolidines, piperidines, and tetrahydroisoquinolines through alkylation with alkenes. While the practicality of these simple carbamate‐type auxiliaries is underscored by the ease of installation and removal, the method's utility is demonstrated in its ability to functionalize biologically relevant l ‐proline and l ‐trans ‐hydroxyproline, delivering unique 2,5‐dialkylated amino acid analogues that are not accessible by other C−H functionalization methods. 相似文献
17.
Honghe Li Xiaoqiang Yan Jitan Zhang Weicong Guo Jijun Jiang Jun Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(20):6804-6808
The first enantioselective Satoh–Miura‐type reaction is reported. A variety of C?N axially chiral N‐aryloxindoles have been enantioselectively synthesized by an asymmetric rhodium‐catalyzed dual C?H activation reaction of N‐aryloxindoles and alkynes. High yields and enantioselectivities were obtained (up to 99 % yield and up to 99 % ee). To date, it is also the first example of the asymmetric synthesis of C?N axially chiral compounds by such a C?H activation strategy. 相似文献
18.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(47):15259-15263
Chemoselective hydroarylations were accomplished by a novel synergistic Brønsted acid/manganese(I)‐catalyzed C−H activation manifold. Thus, alkynes bearing O‐leaving groups could, for the first time, be employed for C−H alkenylations without concurrent β‐O elimination, thereby setting the stage for versatile late‐stage diversifications. Also described is the first manganese‐catalyzed C−H activation in continuous flow, thus enabling efficient hydroarylations within only 20 minutes. 相似文献
19.
Biao Ma Peng Wu Xing Wang Zhengyu Wang Hai‐Xia Lin Hui‐Xiong Dai 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(38):13469-13473
A rhodium(III)‐catalyzed domino annulation of simple olefins with diazo oxindoles to give spirooxindole pyrrolone products is described. This reaction can be formally viewed as the result of an anomalous tandem C?H activation, carbene insertion, Lossen rearrangement, and a nucleophilic addition process. The potential utility of this reaction was further demonstrated by the late‐stage diversification of drug molecules. 相似文献
20.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(36):11060-11063
A Pd‐catalyzed spirocyclization involving a sequential carbopalladation, intramolecular C−H activation, and a highly regioselective alkyne insertion to afford spirooxindoles and spirodihydrobenzofurans has been achieved. The spirocyclic products were generated in good to excellent yields with complete regiocontrol in a readily scalable procedure. 相似文献