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1.
Andrew Whyte Jonathan Bajohr Alexa Torelli Prof. Dr. Mark Lautens 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(38):16551-16555
We report a cobalt-catalyzed hydroacylation of 1,6-enynes with exogenous aldehydes in a domino sequence to construct enantioenriched ketones. The products were obtained in good yields with excellent regio-, diastereo-, and enantioselectivity. Furthermore, the chiral products served as valuable precursors to access complex spirocyclic scaffolds with three contiguous stereocenters. The asymmetric hydroacylation process exhibited no C−H crossover and no KIE, thus indicating that the C−H bond cleavage was not involved in the turnover-limiting step. 相似文献
2.
Rahul K. Shukla Akshay M. Nair Salman Khan Prof. Chandra M. R. Volla 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(39):17190-17196
An efficient Cp*CoIII-catalyzed C8-dienylation of quinoline-N-oxides was achieved by employing allenes bearing leaving groups at the α-position as the dienylating agents. The reaction proceeds by CoIII-catalyzed C−H activation of quinoline-N-oxides and regioselective migratory insertion of the allene followed by a β-oxy elimination, leading to overall dienylation. Site-selective C−H activation was achieved with excellent selectivity under mild reaction conditions, and 30 mol % of a NaF additive was found to be crucial for the efficient dienylation. The methodology features high stereoselectivity, mild reaction conditions, and good functional-group tolerance. C8-alkenylation of quinoline-N-oxides was achieved in the case of allenes devoid of leaving groups as coupling partners. Furthermore, gram-scale preparation and preliminary mechanistic experiments were carried out to gain insights into the reaction mechanism. 相似文献
3.
Raj N. Patel Dharmik M. Patel Nileshkumar B. Rathod Dinesh G. Thakur Sachinkumar D. Patel Srinu Tothadi Subhash Chandra Ghosh 《European journal of organic chemistry》2023,26(34):e202300669
A cobalt-catalyzed, N,O-bidentate directing group-assisted C−H bond functionalization of benzamides with maleimides was developed for the facile access to isoindolone spirosuccinimides in good to excellent yields. This C−H bond activation and spirocyclization employing pyridine N-oxide as directing group provided very good substrate scope and tolerated various functional groups. Furthermore, the mechanistic investigation revealed that the C−H bond activation is the rate-determining step of this reaction. 相似文献
4.
Dr. Qingqing Bu Dr. Elżbieta Gońka Dr. Krzysztof Kuciński Prof. Dr. Lutz Ackermann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(9):2213-2216
Versatile direct Hiyama-type C−H arylations of benzamides were accomplished with organosiloxanes by chelation-assisted cobalt catalysis. The C−H arylation featured broad substrate scope, including challenging C(sp3)−H activation, the use of γ-valerolactone as biomass-derived solvent, and selectively provided the desired biaryls, even when being highly sterically hindered. 相似文献
5.
Chamila Manankandayalage Dr. Daniel K. Unruh Prof. Dr. Clemens Krempner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(20):6263-6273
The intramolecular “inverse” frustrated Lewis pairs (FLPs) of general formula 1-BR2-2-[(Me2N)2C=N]-C6H4 ( 3 – 6 ) [BR2=BMes2 ( 3 ), BC12H8, ( 4 ), BBN ( 5 ), BBNO ( 6 )] were synthesized and structurally characterized by multinuclear NMR spectroscopy and X-ray analysis. These novel types of pre-organized FLPs, featuring strongly basic guanidino units rigidly linked to weakly Lewis acidic boryl moieties via an ortho-phenylene linker, are capable of activating H−H, C−H, N−H, O−H, Si−H, B−H and C=O bonds. 4 and 5 deprotonated terminal alkynes and acetylene to form the zwitterionic borates 1-(RC≡C-BR2)-2-[(Me2N)2C=NH]-C6H4 (R=Ph, H) and reacted with ammonia, BnNH2 and pyrrolidine, to generate the FLP adducts 1-(R2HN→BR2)-2-[(Me2N)2C=NH]-C6H4, where the N-H functionality is activated by intramolecular H-bond interactions. In addition, 5 was found to rapidly add across the double bond of H2CO, PhCHO and PhNCO to form cyclic zwitterionic guanidinium borates in excellent yields. Likewise, 5 is capable of cleaving H2, HBPin and PhSiH3 to form various amino boranes. Collectively, the results demonstrate that these new types of intramolecular FLPs featuring weakly Lewis acidic boryl and strongly basic guanidino moieties are as potent as conventional intramolecular FLPs with strongly Lewis acidic units in activating small molecules. 相似文献
6.
Cobalt‐Catalyzed Intramolecular Reactions between a Vinylcyclopropane and an Alkyne: Switchable [5+2] Cycloaddition and Homo‐Ene Pathways
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Dr. Chunlin Wu Prof. Dr. Naohiko Yoshikai 《Angewandte Chemie (International ed. in English)》2018,57(22):6558-6562
Cobalt–diphosphine catalysts have been found to promote intramolecular reactions between a vinylcyclopropane and an alkyne to selectively afford either the [5+2] cycloaddition product or the homo‐ene reaction product under solvent control. The former product is exclusively formed in noncoordinating 1,2‐dichloroethane, whereas the latter is dominant in coordinating solvents, such as acetonitrile and dimethylacetamide. Furthermore, a highly enantioselective variant of the homo‐ene reaction afforded chiral tetrahydrofuran, pyrrolidine, and cyclopentane derivatives bearing 1,3‐diene and alkylidene substituents. 相似文献
7.
Tingting Li Dr. Gerald B. Hammond Dr. Bo Xu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(38):9737-9741
A widely applicable approach was developed to synthesize ketones, esters, amides via the oxidative C−C bond cleavage of readily available alkyl aldehydes. Green and abundant molecular oxygen (O2) was used as the oxidant, and base metals (cobalt and copper) were used as the catalysts. This strategy can be extended to the one-pot synthesis of ketones from primary alcohols and α-ketoamides from aldehydes. 相似文献
8.
Dr. Yungen Liu Dr. Chun-Wai Tse Dr. Kar-Yee Lam Dr. Xiao-Yong Chang Dr. Xiangguo Guan Meng-Yao Chao Dr. Jie-Sheng Huang Prof. Dr. Chi-Ming Che 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(46):10828-10833
Ruthenium(II) complexes bearing a tridentate bis(N-heterocyclic carbene) ligand reacted with iminoiodanes (PhI=NR) resulting in the formation of isolable ruthenium(III)–amido intermediates, which underwent cleavage of a C−N bond of the tridentate ligand and formation of an N-substituted imine group. The RuIII–amido intermediates have been characterized by 1H NMR, UV/Vis, ESI-MS, and X-ray crystallography. DFT calculations were performed to provide insight into the reaction mechanism. 相似文献
9.
Farheen Fatima Khan Sebastian Sobottka Prof. Dr. Biprajit Sarkar Prof. Goutam Kumar Lahiri 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(41):9737-9746
In the recent years, there has been an emerging research interest in the domain of C−C bond-cleavage reactions. The present contribution deals with the redox-mediated dioxygen activation and C−C bond cleavage in a diruthenium complex [(acac)2RuII(μ-L1)RuII(acac)2], 1 (acac=acetylacetonate) incorporating 2,2′-pyridil (L1) as the bridging ligand. The above process leads to a C−C-cleaved monomeric product [(acac)2RuIII(pic−)], 2 (pic−=piconilate). Intriguingly, similar diastereomeric complexes [(acac)2RuII(μ-L2)RuII(acac)2], meso (ΔΛ): 3 a and rac (ΔΔ/ΛΛ): 3 b , involving an analogous diimine bridge (L2=N1,N2-diphenyl-1,2-di(pyridin-2-yl)ethane-1,2-diimine), were stable towards such oxidative transformations. Electrochemical and spectroelectrochemical studies, in combination, establish the potential non-innocent feature of the 2,2′-Pyridil (L1) and its derivative (L2) both in oxidation and reduction processes. Additionally, theoretical calculations have been employed to verify the redox states and their behavior. Furthermore, transition state (TS) calculations at the M06L/6-31G*/LANL2DZ level of theory together with detailed kinetic studies outline a putative mechanism for the selective transformation of 1 → 2 involving the formation of an intermediate bearing peroxide linkage to complex 1 . 相似文献
10.
11.
Daniel Bafaluy Zoritsa Georgieva Prof. Dr. Kilian Muñiz 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(34):14347-14351
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
12.
Dr. Fengkai He Dr. Christophe Gourlaouen Prof. Dr. Huan Pang Prof. Dr. Pierre Braunstein 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(10):e202104234
Using a pincer platform based on a bridgehead NHC donor with functional side arms, the combined effect of increased flexibility in six-membered pyrimidine-type heterocycles compared to the more often studied five-membered imidazole, and rigidity of phosphane side arms was examined. The unique features observed include: 1) the reaction of the azolium Csp2−H bond with [Ni(cod)2] affording a carbanionic ligand in [NiCl(PCsp3HP)] ( 8 ) rather than a carbene; 2) its transformation into the NHC, hydrido complex [NiH(PCNHCP)]PF6 ( 9 ) upon halide abstraction; 3) ethylene insertion into the Ni−H bond of the latter and ethyl migration to the N−C−N carbon atom of the heterocycle in [Ni(PCEtP)]PF6 ( 10 ); and 4) an unprecedented C−P bond activation transforming the P−CNHC−P pincer ligand of 8 in a C−CNHC−P pincer and a terminal phosphanido ligand in [Ni(PPh2)(CCNHCP)] ( 15 ). The data are supported by nine crystal structure determinations and theoretical calculations provided insights into the mechanisms of these transformations, which are relevant to stoichiometric and catalytic steps of general interest. 相似文献
13.
Metal-Free,Visible-Light-Induced Selective C−C Bond Cleavage of Cycloalkanones with Molecular Oxygen
Hong Xin Prof. Dr. Xin-Hua Duan Dr. Le Liu Prof. Dr. Li-Na Guo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(51):11690-11694
A metal-free, visible-light-induced oxidative C−C bond cleavage of cycloketones with molecular oxygen is described. Cooperative Brønsted-acid catalysis and photocatalysis enabled selective C−C bond cleavage of cycloketones to generate an array of γ-, δ- and ϵ-keto esters under very mild conditions. Mechanistic studies indicate that singlet molecular oxygen (1O2) is responsible for this transformation. 相似文献
14.
Tatsuyoshi Ito Prof. Dr. Nobuharu Iwasawa Dr. Jun Takaya 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(29):12011-12015
An unprecedented photo-promoted skeletal rearrangement reaction of phosphine–borane frustrated Lewis pairs, o-(borylaryl)phosphines, involving cleavage of an unstrained sp2C–sp3C σ-bond is reported. The reaction realizes an efficient synthesis of cyclic phosphonium borate compounds. The reaction mechanism via a boranorcaradiene intermediate is proposed based on theoretical calculations. This work sheds light on the new photoreactivity of phosphine–borane FLPs. 相似文献
15.
Dr. Akira Matsumoto Bich-Ngoc Nguyen Tsubasa Honda Dr. Ryu Sakamoto Dr. Xiao Huang Prof. Dr. Shigeyoshi Sakaki Prof. Dr. Keiji Maruoka 《化学:亚洲杂志》2021,16(4):282-286
This article describes the synthetic application of ketone-derived oxaziridines as alkyl radical precursors in copper-catalyzed Carbon-Carbon bond formation reactions. Experimental and computational studies indicate a free radical mechanism, where alkyl radicals are efficiently generated via cleavage of a Carbon-Carbon bond of oxaziridines. Acyclic and unstrained cyclic oxaziridines are applicable to the present radical process, allowing for the generation of various alkyl radicals with good functional group compatibility. 相似文献
16.
Chun Gu Dr. Weiqiang Yu Hanqing Zhao Prof. Dr. Song Shi Dr. Penghua Che Prof. Dr. Jie Xu Prof. Dr. Jin Gao 《ChemCatChem》2024,16(2):e202301169
A series of porous silica were prepared by alkyl-trimethyl-ammonium bromide with different carbon chain lengths (PS-n, n corresponds to the carbon chain length). These templates carried out precise structure regulation of porous silica. The Ru particles supported on porous silica behaved in precisely controlled size according to the pore diameter. When used in the hydrogenolysis of biomass polyols, a higher methane yield was achieved over Ru/PS-16. This result can be explained by the higher C2/C3 over Ru/PS-16 than others. 相似文献
17.
Andrew Whyte Jonathan Bajohr Alexa Torelli Mark Lautens 《Angewandte Chemie (International ed. in English)》2020,59(38):16409-16413
We report a cobalt‐catalyzed hydroacylation of 1,6‐enynes with exogenous aldehydes in a domino sequence to construct enantioenriched ketones. The products were obtained in good yields with excellent regio‐, diastereo‐, and enantioselectivity. Furthermore, the chiral products served as valuable precursors to access complex spirocyclic scaffolds with three contiguous stereocenters. The asymmetric hydroacylation process exhibited no C?H crossover and no KIE, thus indicating that the C?H bond cleavage was not involved in the turnover‐limiting step. 相似文献
18.
A facile and convenient synthesis of the chiral phthalide framework catalyzed by cationic iridium was developed. The method utilized cationic iridium/bisphosphine‐catalyzed asymmetric intramolecular carbonyl hydroacylation of 2‐keto benzaldehydes to furnish the corresponding optically active phthalide products in good to excellent enantioselectivities (up to 98% ee). The mechanistic studies using a deuterium‐labelled substrate suggested that the reaction involved an intramolecular carbonyl insertion mechanism to iridium hydride intermediate. In addition, we investigated the kinetic isotope effect (KIE) of intramolecular hydroacylation with deuterated substrate and determined that the C?H activation step is not included in the turnover‐limiting step. 相似文献
19.
Dr. Damian Pleschka Marten Uebing Dr. Merten Lange Dr. Alexander Hepp Anna-Lena Wübker Prof. Dr. Michael Ryan Hansen Prof. Dr. Ernst-Ulrich Würthwein Prof. Dr. Werner Uhl 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(39):9315-9325
Al/P- and Ga/P-based frustrated Lewis pairs (FLPs) reacted with an azirine under mild conditions under cleavage of the heterocycle on two different positions. Opening of the C−C bond yielded an unusual nitrile–ylide adduct in which a C−N moiety coordinated to the FLP backbone. Cleavage of a C−N bond afforded the thermodynamically favored enamine adduct with the N atom bound to P and Al or Ga atoms. Ring closure was observed upon treatment of an Al/P FLP with electronically unsaturated substrates (4-(1-cyclohexenyl)-1-aza-but-1-en-3-ynes) and yielded by C−N bond formation hexahydroquinoline derivatives, which coordinated to the FLP through P−C and Al−C bonds. Diphenylcyclopropenone showed a diverse reactivity, which depending on steric shielding and the polarizing effect of Al or Ga atoms afforded different products. An AltBu2/P FLP yielded an adduct with the C=O group coordinated to P and Al. The dineopentyl derivative gave an equilibrium mixture consisting of a similar product and a simple adduct with O bound to Al and a three-coordinate P atom. Both compounds co-crystallize. The Ga/P FLP only formed the simple adduct with the same substrate. Rearrangement resulted in all cases in C3-ring cleavage and migration of a mesityl group from P to a former ring C atom by C−C bond formation. Diphenylthiocyclopropenone (evidence for the presence of P=C bonds) and an imine derivative afforded similar products. 相似文献
20.
Huihui Luo Dr. Lianyue Wang Dr. Sensen Shang Guosong Li Ying Lv Prof. Shuang Gao Dr. Wen Dai 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(43):19430-19436
Selective cleavage and functionalization of C−C bonds have important applications in organic synthesis and biomass utilization. However, functionalization of C−C bonds by controlled cleavage remains difficult and challenging because they are inert. Herein, we describe an unprecedented efficient protocol for the breaking of successive C−C bonds in alcohols to form esters with one or multiple carbon atoms less using heterogeneous cobalt nanoparticles as catalyst with dioxygen as the oxidant. A wide range of alcohols including inactive long-chain alkyl aryl alcohols undergo smoothly successive cleavage of adjacent −(C−C)n− bonds to afford the corresponding esters. The catalyst was used for seven times without any decrease in activity. Characterization and control experiments disclose that cobalt nanoparticles are responsible for the successive cleavage of C−C bonds to achieve excellent catalytic activity, while the presence of Co-Nx has just the opposite effect. Preliminary mechanistic studies reveal that a tandem sequence reaction is involved in this process. 相似文献