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1.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(9):2518-2521
Carbon–carbon bond cleavage/functionalization is synthetically valuable, and selective carbonyl−C(sp3) bond cleavage/alkynylation presents a new perspective in constructing ynamides, ynoates, and ynones. Reported here is the first alkoxyl‐radical‐enabled carbonyl−C(sp3) bond cleavage/alkynylation reaction by photoredox catalysis. The use of novel cyclic iodine(III) reagents are essential for β‐carbonyl alkoxyl radical generation from β‐carbonyl alcohols, including alcohols with high redox potential ( >2.2 V vs. SCE in MeCN). β‐Amide, β‐ester, and β‐ketone alcohols yield ynamides, ynoates, and ynones, respectively, for the first time, with excellent regio‐ and chemoselectivity under mild reaction conditions. 相似文献
2.
《Angewandte Chemie (International ed. in English)》2017,56(9):2478-2481
Carbon–carbon bond cleavage/functionalization is synthetically valuable, and selective carbonyl−C(sp3) bond cleavage/alkynylation presents a new perspective in constructing ynamides, ynoates, and ynones. Reported here is the first alkoxyl‐radical‐enabled carbonyl−C(sp3) bond cleavage/alkynylation reaction by photoredox catalysis. The use of novel cyclic iodine(III) reagents are essential for β‐carbonyl alkoxyl radical generation from β‐carbonyl alcohols, including alcohols with high redox potential ( >2.2 V vs. SCE in MeCN). β‐Amide, β‐ester, and β‐ketone alcohols yield ynamides, ynoates, and ynones, respectively, for the first time, with excellent regio‐ and chemoselectivity under mild reaction conditions. 相似文献
3.
Control of chemoselectivity is one of the most challenging problems facing chemists and is particularly important in the synthesis of bioactive compounds and medications. Herein, the first highly chemoselective tandem C(sp3)–H arylation/[1,2]-Wittig rearrangement of pyridylmethyl ethers is presented. The efficient and operationally simple protocols enable generation of either arylation products or tandem arylation/[1,2]-Wittig rearrangement products with remarkable selectivity and good to excellent yields (60–99%). Choice of base, solvent, and reaction temperature play a pivotal role in tuning the reactivity of intermediates and controlling the relative rates of competing processes. The novel arylation step is catalyzed by a Pd(OAc)2/NIXANTPHOS-based system via a deprotonative cross-coupling process. The method provides rapid access to skeletally diverse aryl(pyridyl)methanol core structures, which are central components of several medications. 相似文献
4.
MnI/AgI Relay Catalysis: Traceless Diazo‐Assisted C(sp2)–H/C(sp3)–H Coupling to β‐(Hetero)Aryl/Alkenyl Ketones
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Dr. Qingquan Lu Shobhan Mondal Dr. Sara Cembellín Prof. Dr. Frank Glorius 《Angewandte Chemie (International ed. in English)》2018,57(33):10732-10736
An unprecedented MnI/AgI‐relay‐catalyzed C(sp2)?H/C(sp3)?H coupling of (vinyl)arenes with α‐diazoketones is reported, wherein the diazo group was exploited as a traceless auxiliary for control of regioselectivity. Challenging β‐(hetero)aryl/alkenyl ketones were obtained through this operationally simple approach. The cascade process merges denitrogenation, carbene rearrangement, C?H activation, and hydroarylation/hydroalkenylation. The robustness of this method was demonstrated at preparative scale and applied to late‐stage diversification of natural products. 相似文献
5.
Construction of Hexahydrophenanthrenes By Rhodium(I)‐Catalyzed Cycloisomerization of Benzylallene‐Substituted Internal Alkynes through C−H Activation
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Yasuaki Kawaguchi Dr. Shigeo Yasuda Prof. Dr. Chisato Mukai 《Angewandte Chemie (International ed. in English)》2016,55(35):10473-10477
The treatment of benzylallene‐substituted internal alkynes with [RhCl(CO)2]2 effects a novel cycloisomerization by C(sp2)?H bond activation to produce hexahydrophenanthrene derivatives. The reaction likely proceeds through consecutive formation of a rhodabicyclo[4.3.0] intermediate, σ‐bond metathesis between the C(sp2)?H bond on the benzene ring and the C(sp2)?RhIII bond, and isomerization between three σ‐, π‐, and σ‐allylrhodium(III) species, which was proposed based on experiments with deuterated substrates. 相似文献
6.
Catalyst‐Free Three‐Component Tandem CDC Cyclization: Convenient Access to Isoindolinones from Aromatic Acid,Amides, and DMSO by a Pummerer‐Type Rearrangement
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Peng‐Min Wang Fan Pu Ke‐Yan Liu Prof. Dr. Chao‐Jun Li Prof. Dr. Zhong‐Wen Liu Dr. Xian‐Ying Shi Juan Fan Dr. Ming‐Yu Yang Prof. Dr. Jun‐Fa Wei 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(18):6262-6267
A catalyst‐free multicomponent CDC reaction is rarely reported, especially for the intermolecular tandem CDC cyclization, which represents an important strategy for constructing cyclic compounds. Herein, a three‐component tandem CDC cyclization by a Pummerer‐type rearrangement to afford biologically relevant isoindolinones from aromatic acids, amides, and DMSO, is described. This intermolecular tandem reaction undergoes a C(sp2)?H/C(sp3)?H cross‐dehydrogenative coupling, C?N bond formation, and intramolecular amidation. A notable feature of this novel protocol is avoiding a catalyst and additive (apart from oxidant). 相似文献
7.
Ethan A. Wappes Stacy C. Fosu Trevor C. Chopko Prof. Dr. David A. Nagib 《Angewandte Chemie (International ed. in English)》2016,55(34):9974-9978
The Cδ?H amination of unactivated, secondary C?H bonds to form a broad range of functionalized pyrrolidines has been developed by a triiodide (I3?)‐mediated strategy. By in situ 1) oxidation of sodium iodide and 2) sequestration of the transiently generated iodine (I2) as I3?, this approach precludes undesired I2‐mediated decomposition which can otherwise limit synthetic utility to only weak C(sp3)?H bonds. The mechanism of this triiodide‐mediated cyclization of unbiased, secondary C(sp3)?H bonds, by either thermal or photolytic initiation, is supported by NMR and UV/Vis data, as well as intercepted intermediates. 相似文献
8.
Fehr C Vuagnoux M Buzas A Arpagaus J Sommer H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(22):6214-6220
In the search for a new access to thujopsanone related compounds by cycloisomerization reactions of unsaturated propargylic alcohols and acetates, we found several interesting reaction types and demonstrated the complementarity of Au, Pt, and Cu catalysts. Thus, 6‐en‐1‐yn‐3‐ol 10 a underwent clean cyclization/ether formation to 16 , in particular using Au catalysts (76–98 %) or a newly prepared CuI‐ triflimidate‐catalyst (94 %). The corresponding acetate 11 a underwent either the cycloisomerization with concomitant [1,2]‐acyl shift (to 12 : 78 % using AuCl3) or an unprecedented rearrangement‐cycloaddition leading to 20 (43 % using [(tBuXPhos)AuNTf2]), a strained fused tricyclic ring system containing a [2.2.0] bicyclic subunit. 相似文献
9.
Synthesis of Peptides by Silver‐Promoted Coupling of Carboxylates and Thioamides: Mechanistic Insight from Computational Studies
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Prof. Craig A. Hutton Jing Shang Prof. Uta Wille 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(9):3163-3169
The mechanism of the recently described N→C direction peptide synthesis through silver‐promoted coupling of N‐protected amino acids with thioacetylated amino esters was explored by using density functional theory. Calculation of the potential energy surfaces for various pathways revealed that the reaction proceeds through silver‐assisted addition of the carboxylate to the thioamide, which is followed by deprotonation and silver‐mediated extrusion of sulfur as Ag2S. The resulting isoimide is the key intermediate, which subsequently rearranges to an imide through a concerted pericyclic [1,3]‐acyl shift (O–sp2N 1,3‐acyl migration). The proposed mechanism clearly emphasises the requirement of two equivalents of AgI and basic reaction conditions, which is in full agreement with the experimental findings. Alternative rearrangement pathways involving only one equivalent of AgI or through O–sp3N 1,3‐acyl migration can be excluded. The computations further revealed that peptide couplings involving thioformamides require significant conformational changes in the intermediate isoformimide, which slow down the rearrangement process. 相似文献
10.
Dr. Chun-Xiao Li Qian Ning Wenxuan Zhao Hou-Ji Cao Yi-Ping Wang Prof. Dr. Hong Yan Prof. Dr. Chang-Sheng Lu Prof. Dr. Yong Liang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(8):2699-2706
The convenient cross-coupling of sp2 or sp3 carbons with a specific boron vertex on carborane cage represents significant synthetic values and insurmountable challenges. In this work, we report an Rh-catalyzed reaction between o-carborane and N-acyl-glutarimides to construct various Bcage−C bonds. Under the optimized condition, the removable imine directing group (DG) leads to B(3)− or B(3,6)−C couplings, while the pyridyl DG leads to B(3,5)−Ar coupling. In particular, an unexpected rearrangement of amide reagent is observed in pyridyl directed B(4)−C(sp3) formation. This scalable protocol has many advantages, including easy access, the use of cheap and widely available coupling agents, no requirement of an external ligand, base or oxidant, high efficiency, and a broad substrate scope. Leveraging the RhI dimer and twisted amides, this method enables straightforward access to diversely substituted and therapeutically important carborane derivatives at boron site, and provides a highly valuable vista for carborane-based drug screening. 相似文献
11.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(49):15889-15893
Reported herein is a novel visible‐light photoredox system with Pd(PPh3)4 as the sole catalyst for the realization of the first direct cross‐coupling of C(sp3)−H bonds in N‐aryl tetrahydroisoquinolines with unactivated alkyl bromides. Moreover, intra‐ and intermolecular alkylations of heteroarenes were also developed under mild reaction conditions. A variety of tertiary, secondary, and primary alkyl bromides undergo reaction to generate C(sp3)−C(sp3) and C(sp2)−C(sp3) bonds in moderate to excellent yields. These redox‐neutral reactions feature broad substrate scope (>60 examples), good functional‐group tolerance, and facile generation of quaternary centers. Mechanistic studies indicate that the simple palladium complex acts as the visible‐light photocatalyst and radicals are involved in the process. 相似文献
12.
Zhen Wang Jizhi Ni Prof. Dr. Yoichiro Kuninobu Prof. Dr. Motomu Kanai 《Angewandte Chemie (International ed. in English)》2014,53(13):3496-3499
The first copper‐catalyzed intramolecular C(sp3)? H and C(sp2)? H oxidative amidation has been developed. Using a Cu(OAc)2 catalyst and an Ag2CO3 oxidant in dichloroethane solvent, C(sp3)? H amidation proceeded at a terminal methyl group, as well as at the internal benzylic position of an alkyl chain. This reaction has a broad substrate scope, and various β‐lactams were obtained in excellent yield, even on gram scale. Use of CuCl2 and Ag2CO3 under an O2 atmosphere in dimethyl sulfoxide, however, leads to 2‐indolinone selectively by C(sp2)? H amidation. Kinetic isotope effect (KIE) studies indicated that C? H bond activation is the rate‐determining step. The 5‐methoxyquinolyl directing group could be removed by oxidation. 相似文献
13.
Zhen Wang Jizhi Ni Yoichiro Kuninobu Motomu Kanai 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(13):3564-3567
The first copper‐catalyzed intramolecular C(sp3) H and C(sp2) H oxidative amidation has been developed. Using a Cu(OAc)2 catalyst and an Ag2CO3 oxidant in dichloroethane solvent, C(sp3) H amidation proceeded at a terminal methyl group, as well as at the internal benzylic position of an alkyl chain. This reaction has a broad substrate scope, and various β‐lactams were obtained in excellent yield, even on gram scale. Use of CuCl2 and Ag2CO3 under an O2 atmosphere in dimethyl sulfoxide, however, leads to 2‐indolinone selectively by C(sp2) H amidation. Kinetic isotope effect (KIE) studies indicated that C H bond activation is the rate‐determining step. The 5‐methoxyquinolyl directing group could be removed by oxidation. 相似文献
14.
Anton Dmitrienko Prof. Melanie Pilkington Dr. James F. Britten Dr. Bulat M. Gabidullin Prof. Art van der Est Prof. Georgii I. Nikonov 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(37):16281-16287
The aluminum(I) compound NacNacAl (NacNac=[ArNC(Me)CHC(Me)NAr]−, Ar=2,6-iPr2C6H3, 1 ) shows diverse and substrate-controlled reactivity in reactions with N-heterocycles. 4-Dimethylaminopyridine (DMAP), a basic substrate in which the 4-position is blocked, induces rearrangement of NacNacAl by shifting a hydrogen atom from the methyl group of the NacNac backbone to the aluminum center. In contrast, C−H activation of the methyl group of 4-picoline takes place to produce a species with a reactive terminal methylene. Reaction of 1 with 3,5-lutidine results in the first example of an uncatalyzed, room-temperature cleavage of an sp2 C−H bond (in the 4-position) by an AlI species. Another reactivity mode was observed for quinoline, which undergoes 2,2′-coupling. Finally, the reaction of 1 with phthalazine produces the product of N−N bond cleavage. 相似文献
15.
Xiaoyuan Ying Dr. Yuxi Li Luyang Li Dr. Chao Li 《Angewandte Chemie (International ed. in English)》2023,62(26):e202304177
Despite several methodologies established for C(sp2)−I selective C(sp2)−C(sp3) bond formations, achieving arene-flanked quaternary carbons by cross-coupling of tertiary alkyl precursors with bromo(iodo)arenes in a C(sp2)−I selective manner is rare. Here we report a general Ni-catalyzed C(sp2)−I selective cross-electrophile coupling (XEC) reaction, in which, beyond 3° alkyl bromides (for constructing arene-flanked quaternary carbons), 2° and 1° alkyl bromides are also demonstrated to be viable coupling partners. Moreover, this mild XEC displays excellent C(sp2)−I selectivity and functional group compatibility. The practicality of this XEC is demonstrated in simplifying the routes to several medicinally relevant and synthetically challenging compounds. Extensive experiments show that the terpyridine-ligated NiI halide can exclusively activate alkyl bromides, forming a NiI−alkyl complex through a Zn reduction. Attendant density functional theory (DFT) calculations reveal two different pathways for the oxidative addition of the NiI−alkyl complex to the C(sp2)−I bond of bromo(iodo)arenes, explaining both the high C(sp2)−I selectivity and generality of our XEC. 相似文献
16.
Gold‐Catalyzed Cycloisomerization of 1,6,8‐Dienyne Carbonates and Esters to cis‐Cyclohepta‐4,8‐diene‐Fused Pyrrolidines
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Dr. Weidong Rao Sally Stuart Neil Berry Prof. Dr. Philip Wai Hong Chan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(41):13174-13180
A synthetic approach that provides access to cis‐cyclohepta‐4,8‐diene‐fused pyrrolidines efficiently through AuI‐catalyzed cycloisomerization of 1,6,8‐dienyne carbonates and esters at a low catalyst loading of 2 mol % is reported. Starting carbonates and esters with a pendant alkyl group on the terminal alkenyl carbon center were found to favor tandem 1,2‐acyloxy migration/cyclopropanation followed by Cope rearrangement of the resulting cis‐3‐azabicyclo[3.1.0]hexane intermediate. On the other hand, substrates containing a terminal diene or starting materials in which the distal alkene moiety bears a phenyl substituent were observed to undergo competitive but reversible 1,3‐acyloxy migration prior to the nitrogen‐containing bicyclic ring formation. The delineated reaction mechanism also provides experimental evidence for the reversible interconversion between the oft‐proposed organogold intermediates obtained in this step of the tandem process. 相似文献
17.
Yong Zhang Min Yang Chengli Jia Prof. Min Ji 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(60):13709-13713
A method for the synthesis of novel fused four-ring quinoxaline skeleton has been described by an I2 promoted sp3 C−H functionalization between 1,2,3,3-tetramethyl-3H-indolium iodides and 1,2-diamines. This transformation proceeds smoothly under metal- and peroxide-free conditions through a sequential iodination, oxidation, annulation and rearrangement. Moreover, 8,9-dichloro-5,12,12-trimethyl-2-(trifluoromethyl)-5,12-dihydroquinolino[2,3-b]quinoxaline showed good photophysical properties and was used in live cell imaging, indicating the potential value of this skeleton as a fluorophore in probes. 相似文献
18.
Mechanistic Insights into the Ni‐Catalyzed Reductive Carboxylation of C−O Bonds in Aromatic Esters with CO2: Understanding Remarkable Ligand and Traceless‐Directing‐Group Effects
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Yan‐Li Han Bing‐Yuan Zhao Kun‐Yao Jiang Hui‐Min Yan Dr. Zhu‐Xia Zhang Dr. Wen‐Jing Yang Prof. Dr. Zhen Guo Prof. Dr. Yan‐Rong Li 《化学:亚洲杂志》2018,13(12):1570-1581
The mechanism of the Ni0‐catalyzed reductive carboxylation reaction of C(sp2)?O and C(sp3)?O bonds in aromatic esters with CO2 to access valuable carboxylic acids was comprehensively studied by using DFT calculations. Computational results revealed that this transformation was composed of several key steps: C?O bond cleavage, reductive elimination, and/or CO2 insertion. Of these steps, C?O bond cleavage was found to be rate‐determining, and it occurred through either oxidative addition to form a NiII intermediate, or a radical pathway that involved a bimetallic species to generate two NiI species through homolytic dissociation of the C?O bond. DFT calculations revealed that the oxidative addition step was preferred in the reductive carboxylation reactions of C(sp2)?O and C(sp3)?O bonds in substrates with extended π systems. In contrast, oxidative addition was highly disfavored when traceless directing groups were involved in the reductive coupling of substrates without extended π systems. In such cases, the presence of traceless directing groups allowed for docking of a second Ni0 catalyst, and the reactions proceed through a bimetallic radical pathway, rather than through concerted oxidative addition, to afford two NiI species both kinetically and thermodynamically. These theoretical mechanistic insights into the reductive carboxylation reactions of C?O bonds were also employed to investigate several experimentally observed phenomena, including ligand‐dependent reactivity and site‐selectivity. 相似文献
19.
Anton Dmitrienko Melanie Pilkington James F. Britten Bulat M. Gabidullin Art van der Est Georgii I. Nikonov 《Angewandte Chemie (International ed. in English)》2020,59(37):16147-16153
The aluminum(I) compound NacNacAl (NacNac=[ArNC(Me)CHC(Me)NAr]?, Ar=2,6‐iPr2C6H3, 1 ) shows diverse and substrate‐controlled reactivity in reactions with N‐heterocycles. 4‐Dimethylaminopyridine (DMAP), a basic substrate in which the 4‐position is blocked, induces rearrangement of NacNacAl by shifting a hydrogen atom from the methyl group of the NacNac backbone to the aluminum center. In contrast, C?H activation of the methyl group of 4‐picoline takes place to produce a species with a reactive terminal methylene. Reaction of 1 with 3,5‐lutidine results in the first example of an uncatalyzed, room‐temperature cleavage of an sp2 C?H bond (in the 4‐position) by an AlI species. Another reactivity mode was observed for quinoline, which undergoes 2,2′‐coupling. Finally, the reaction of 1 with phthalazine produces the product of N?N bond cleavage. 相似文献
20.
《Arabian Journal of Chemistry》2022,15(7):103896
L-cysteine, a natural and essential amino acid, was employed as novel sulfur source in the synthesis of symmetrical diaryl sulfides from a variety of aryl iodides in moderate to excellent yields. A tandem three steps’ reactions including C(sp2)-S bond formation, C(sp3)-S bond cleavage and another C(sp2)-S bond formation were proposed to be involved in this conversion. This protocol was featured by broad substrate scope and good functional group tolerance. In addition, heteroarenes including benzothiazoles and benzoxazoles were successfully converted into the corresponding heteroarenethiols using L-cysteine as C-H mercaptalization reagent. 相似文献