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1.
We designed and synthesized a heteroleptic osmium(ii) complex with two different tridentate ligands, Os. Os can absorb the full wavelength range of visible light owing to S–T transitions, and this was supported by TD-DFT calculations. Excitation of Os using visible light of any wavelength generates the same lowest triplet metal-to-ligand charge-transfer excited state, the lifetime of which is relatively long (τem = 40 ns). Since excited Os could be reductively quenched by 1,3-dimethyl-2-(o-hydroxyphenyl)-2,3-dihydro-1H-benzo[d]imidazole, Os displays high potential as a panchromatic photosensitizer. Using a combination of Os and a ruthenium(ii) catalyst, CO2 was photocatalytically reduced to HCOOH via irradiation with 725 nm light, and the turnover number reached 81; irradiation with light at λex > 770 nm also photocatalytically induced HCOOH formation. These results clearly indicate that Os can function as a panchromatic redox photosensitizer.The osmium(ii) complex functioned as a panchromatic photosensitizer and drove CO2 reduction. 相似文献
2.
A protocol for the synthesis of α-tertiary amines was developed by iterative addition of carbon nucleophiles to N,N-dialkyl carboxamides. Nucleophilic 1,2-addition of organolithium reagents to carboxamides forms anionic tetrahedral carbinolamine (hemiaminal) intermediates, which are subsequently treated with bromotrimethylsilane (Me3SiBr) followed by organomagnesium (Grignard) reagents, organolithium reagents or tetrabutylammonium cyanide, affording α-tertiary amines. Employment of (trimethylsilyl)methylmagnesium bromide as the 2nd nucleophile allowed for aza-Peterson olefination of the resulting α-tertiary (trimethylsilyl)methylamines with acidic work-up, resulting in the formation of 1,1-diarylethylenes.We herein report a concise protocol for iterative addition of carbon nucleophiles to N,N-dialkyl carboxamides for the synthesis of α-tertiary amines. 相似文献
3.
A tetra(o-tolyl) (μ-hydrido)diborane(4) anion 1, an analogue of [B2H5]− species, was facilely prepared through the reaction of tetra(o-tolyl)diborane(4) with sodium hydride. Unlike common sp2–sp3 diborane species, 1 exhibited a σ-B–B bond nucleophilicity towards NHC-coordinated transition-metal (Cu, Ag, and Au) halides, resulting in the formation of η2-B–B bonded complexes 2 as confirmed by single-crystal X-ray analyses. Compared with 1, the structural data of 2 imply significant elongations of B–B bonds, following the order Au > Cu > Ag. DFT studies show that the diboron ligand interacts with the coinage metal through a three-center-two-electron B–M–B bonding mode. The fact that the B–B bond of the gold complex is much prolonged than the related Cu and Ag compounds might be ascribed to the superior electrophilicity of the gold atom.A tetra(o-tolyl)(μ-hydrido)diborane(4) anion is facilely prepared via the reaction of tetra(o-tolyl)diborane(4) with NaH. It exhibits a σ-B–B bond nucleophilicity towards NHC-metal halides to give the corresponding η2-B–B bonded metal complexes. 相似文献
4.
Mo Yang Sara Sheykhi Yu Zhang Carsten Milsmann Felix N. Castellano 《Chemical science》2021,12(26):9069
The current investigation demonstrates highly efficient photochemical upconversion (UC) where a long-lived Zr(iv) ligand-to-metal charge transfer (LMCT) complex serves as a triplet photosensitizer in concert with well-established 9,10-diphenylanthracene (DPA) along with newly conceived DPA–carbazole based acceptors/annihilators in THF solutions. The initial dynamic triplet–triplet energy transfer (TTET) processes (ΔG ∼ −0.19 eV) featured very large Stern–Volmer quenching constants (KSV) approaching or achieving 105 M−1 with bimolecular rate constants between 2 and 3 × 108 M−1 s−1 as ascertained using static and transient spectroscopic techniques. Both the TTET and subsequent triplet–triplet annihilation (TTA) processes were verified and throughly investigated using transient absorption spectroscopy. The Stern–Volmer metrics support 95% quenching of the Zr(iv) photosensitizer using modest concentrations (0.25 mM) of the various acceptor/annihilators, where no aggregation took place between any of the chromophores in THF. Each of the upconverting formulations operated with continuous-wave linear incident power dependence (λex = 514.5 nm) down to ultralow excitation power densities under optimized experimental conditions. Impressive record-setting ηUC values ranging from 31.7% to 42.7% were achieved under excitation conditions (13 mW cm−2) below that of solar flux integrated across the Zr(iv) photosensitizer''s absorption band (26.7 mW cm−2). This study illustrates the importance of supporting the continued development and discovery of molecular-based triplet photosensitizers based on earth-abundant metals.The LMCT photosensitizer Zr(MesPDPPh)2 paired with DPA-based acceptors enabled low power threshold photochemical upconversion with record-setting quantum efficiencies. 相似文献
5.
Xinwei Li Zengrui Cheng Jianzhong Liu Ziyao Zhang Song Song Ning Jiao 《Chemical science》2022,13(31):9056
C(sp3)–H bond desaturation has been an attractive strategy in organic synthesis. Enamides are important structural fragments in pharmaceuticals and versatile synthons in organic synthesis. However, the dehydrogenation of amides usually occurs on the acyl side benefitting from enolate chemistry like the desaturation of ketones and esters. Herein, we demonstrate an Fe-assisted regioselective oxidative desaturation of amides, which provides an efficient approach to enamides and β-halogenated enamides.A novel and regioselective N-α,β-desaturation and dehydrogenative N-β-halogenation of amides was developed. This chemistry with high selectivity and broad substrate scope provides an efficient approach to enamides from simple amides. 相似文献
6.
Shweta Kalra Daniel Pividori Dominik Fehn Chenshu Dai Shicheng Dong Shenglai Yao Jun Zhu Karsten Meyer Matthias Driess 《Chemical science》2022,13(29):8634
Using the potentially tridentate N,N′-bis(N-heterocyclic silylene)pyridine [SiNSi] pincer-type ligand, 2,6-N,N′-diethyl-bis[N,N′-di-tert-butyl(phenylamidinato)silylene] diaminopyridine, led to the first isolable bis(silylene)pyridine-stabilized manganese(0) complex, {κ3-[SiNSi]Mn(dmpe)} 4 (dmpe = (Me2P)2C2H4), which represents an isolobal 17 VE analogue of the elusive Mn(CO)5 radical. The compound is accessible through the reductive dehalogenation of the corresponding dihalido (SiNSi)Mn(ii) complexes 1 (Cl) and 2 (Br) with potassium graphite. Exposing 4 towards the stronger π-acceptor ligands CO and 2,6-dimethylphenyl isocyanide afforded the related Mn(0) complexes κ2-[SiNSi]Mn(CO)3 (5) and κ3-[SiNSi]Mn(CNXylyl)2(κ1-dmpe) (6), respectively. Remarkably, the stabilization of Mn(0) in the coordination sphere of the [SiNSi] ligand favors the d7 low-spin electronic configuration, as suggested by EPR spectroscopy, SQUID measurements and DFT calculations. The suitability of 4 acting as a superior pre-catalyst in regioselective hydroboration of quinolines has also been demonstrated.An isolable bis(silylene)pyridine stabilized manganese(0) complex {κ3-[SiNSi]Mn(dmpe)}, isolobal to elusive Mn(CO)5 radical has been synthesized and fully characterised. 相似文献
7.
Imlirenla Pongener Dionissia A. Pepe Joseph J. Ruddy Eoghan M. McGarrigle 《Chemical science》2021,12(29):10070
Stereoselective β-mannosylation is one of the most challenging problems in the synthesis of oligosaccharides. Herein, a highly selective synthesis of β-mannosides and β-rhamnosides from glycosyl hemi-acetals is reported, following a one-pot chlorination, iodination, glycosylation sequence employing cheap oxalyl chloride, phosphine oxide and LiI. The present protocol works excellently with a wide range of glycosyl acceptors and with armed glycosyl donors. The method doesn''t require conformationally restricted donors or directing groups; it is proposed that the high β-selectivities observed are achieved via an SN2-type reaction of α-glycosyl iodide promoted by lithium iodide.Breaking from the current paradigm, a highly selective synthesis of hard-to-make β-mannosides and β-rhamnosides from simple glycosyl hemi-acetals has been achieved without using conformational restrictions. 相似文献
8.
Rakesh K. Saunthwal James Mortimer Andrew J. Orr-Ewing Jonathan Clayden 《Chemical science》2022,13(7):2079
Enantioenriched seven-membered carbocycles are motifs in many molecules of structural and biological interest. We report a simple, practical, transition metal-free and mechanistically unusual method for the enantioselective synthesis of substituted cycloheptatrienes. By forming a coloured enolate with an appropriate absorption band and selectively irradiating in situ, we to initiate a tandem, asymmetric anionic and photochemical ring expansion of readily accessible N-benzylbenzamides. The cascade of reactions leading to the products entails enantioselective benzylic deprotonation with a chiral lithium amide, dearomatizing cyclization of the resulting configurationally defined organolithium to give an extended amide enolate, and photochemically induced formal [1,7]-sigmatropic rearrangement and 6π-electrocyclic ring-opening – the latter all evidently being stereospecific – to deliver enantioenriched cycloheptatrienes with embedded benzylic stereocentres.Irradiation of a mixture of aromatic amide and chiral base leads to a tandem reaction sequence in which dearomatization forms a chromophore capable of photochemical rearrangement leading to overall asymmetric expansion of the aromatic ring. 相似文献
9.
Yumin Kim Sangyoon Kang Byung Hun Lee Youngjun Song Sunah Kang Hye Yoon Park Yan Lee 《Chemical science》2022,13(2):365
We discovered the generation of a new bright blue fluorophore from a particular type of amine and 2-oxoglutarate (2-OG) under mild conditions without any chemical additives. Two β-aminoethylamine molecules and three 2-OG molecules form an unprecedented 2-pyridone structure with a fused γ-lactam ring (DTPP) via complex reactions including double decarboxylation and quintuple dehydration. The DTPP fluorophore shows a high quantum yield (80%) and photostability. The great potential of the present DTPP generation in the quantitative analysis of 2-OG in biosamples is demonstrated.DTPP, a bright fluorophore with 2-pyridone and γ-lactam, is generated in a de novo manner from non-fluorogenic 2-oxoglutarate and specific amines. The DTPP-based fluorometry is applied to the analysis of 2-oxoglutarate in a biological sample. 相似文献
10.
Wei Wen Zhao-Pin Ai Chang-Lin Yang Chao-Xing Li Zhu-Lian Wu Tian Cai Qi-Xiang Guo 《Chemical science》2022,13(13):3796
Chiral α-amino ketones are common structural motifs in natural products and pharmaceuticals, as well as important synthons in organic synthesis. Thus, establishing efficient methods for preparing compounds with these privileged scaffolds is an important endeavor in synthetic chemistry. Herein we disclose a new catalytic asymmetric approach for the synthesis of chiral α-amino ketones through a chiral palladium-catalyzed arylation reaction of in situ generated challenging α-keto imines from previously unreported C-acyl N-sulfonyl-N,O-aminals, with arylboronic acids. The current reaction offers a straightforward approach to the asymmetric synthesis of acyclic α-amino ketones in a practical and highly stereocontrolled manner. Meanwhile, the multiple roles of the chiral Pd(ii) complex catalyst in the reaction were also reported.Chiral α-amino ketones are common structural motifs in natural products and pharmaceuticals, as well as important synthons in organic synthesis. 相似文献
11.
Yu Xin Xiaojun Shen Minghua Dong Xiaomeng Cheng Shulin Liu Junjuan Yang Zhenpeng Wang Huizhen Liu Buxing Han 《Chemical science》2021,12(45):15110
The activation and cleavage of C–C bonds remains a critical scientific issue in many organic reactions and is an unmet challenge due to their intrinsic inertness and ubiquity. Meanwhile, it is crucial for the valorization of lignin into high-value chemicals. Here, we proposed a novel strategy to enhance the Caromatic–Cα bond cleavage by pre-functionalization with amine sources, in which an active amine intermediate is first formed through Markovnikov hydroamination to reduce the dissociation energy of the Caromatic–Cα bond which is then cleaved to form target chemicals. More importantly, this strategy provides a method to achieve the maximum utilization of the aromatic nucleus and side chains in lignin or its platform molecules. Phenols and N,N-dimethylethylamine compounds with high yields were produced from herbaceous lignin or the p-coumaric acid monomer in the presence of industrially available dimethylamine (DMA).Pre-functionalization with amine sources mediated the cleavage of Caromatic–Cα bonds to produce two valuable chemicals with high yields, for the full utilization of the aromatic rings and side-chains in lignin and its platform molecules. 相似文献
12.
Li-Hui Mou Yao Li Gong-Ping Wei Zi-Yu Li Qing-Yu Liu Hui Chen Sheng-Gui He 《Chemical science》2022,13(32):9366
The direct coupling of dinitrogen (N2) and methane (CH4) to construct the N–C bond is a fascinating but challenging approach for the energy-saving synthesis of N-containing organic compounds. Herein we identified a likely reaction pathway for N–C coupling from N2 and CH4 mediated by heteronuclear metal cluster anions CoTaC2−, which starts with the dissociative adsorption of N2 on CoTaC2− to generate a Taδ+–Ntδ− (terminal-nitrogen) Lewis acid–base pair (LABP), followed by the further activation of CH4 by CoTaC2N2− to construct the N–C bond. The N N cleavage by CoTaC2− affording two N atoms with strong charge buffering ability plays a key part, which facilitates the H3C–H cleavage via the LABP mechanism and the N–C formation via a CH3 migration mechanism. A novel Nt triggering strategy to couple N2 and CH4 molecules using metal clusters was accordingly proposed, which provides a new idea for the direct synthesis of N-containing compounds.A possible N–C bond formation directly from N2 and CH4 mediated by heteronuclear metal cluster anions CoTaC2− at room temperature was identified. 相似文献
13.
Despite the rapid growth of enantioselective halolactonization reactions in recent years, most are effective only when forming smaller (6,5,4-membered) rings. Seven-membered ε-lactones, are rarely formed with high selectivity, and never without conformational bias. We describe the first highly enantioselective 7-exo-trig iodolactonizations of conformationally unbiased ε-unsaturated carboxylic acids, effected by an unusual combination of a bifunctional BAM catalyst, I2, and I(iii) reagent (PhI(OAc)2:PIDA).We describe the first highly enantioselective 7-exo-trig iodolactonizations of conformationally unbiased ε-unsaturated carboxylic acids, effected by an unusual combination of a bifunctional BAM catalyst, I2, and I(iii) reagent (PhI(OAc)2:PIDA). 相似文献
14.
Nikoleta Kotsina Christian Brahms Sebastian
L. Jackson John C. Travers Dave Townsend 《Chemical science》2022,13(33):9586
We exploit the phenomenon of resonant dispersive wave (RDW) emission in gas-filled hollow capillary fibres (HCFs) to realize time-resolved photoelectron imaging (TRPEI) measurements with an extremely short temporal resolution. By integrating the output end of an HCF directly into a vacuum chamber assembly we demonstrate two-colour deep ultraviolet (DUV)-infrared instrument response functions of just 10 and 11 fs at central pump wavelengths of 250 and 280 nm, respectively. This result represents an advance in the current state of the art for ultrafast photoelectron spectroscopy. We also present an initial TRPEI measurement investigating the excited-state photochemical dynamics operating in the N-methylpyrrolidine molecule. Given the substantial interest in generating extremely short and highly tuneable DUV pulses for many advanced spectroscopic applications, we anticipate our first demonstration will stimulate wider uptake of the novel RDW-based approach for studying ultrafast photochemistry – particularly given the relatively compact and straightforward nature of the HCF setup.We exploit the phenomenon of resonant dispersive wave emission in gas-filled hollow capillary fibres to realize time-resolved photoelectron imaging measurements with an extremely short temporal resolution. 相似文献
15.
Wei-An Chen Yu-Hsin Chen Chiao-Yun Hsieh Pi-Fang Hung Chiao-Wen Chen Chien-Hung Chen Jung-Lee Lin Ting-Jen R. Cheng Tsui-Ling Hsu Ying-Ta Wu Chia-Ning Shen Wei-Chieh Cheng 《Chemical science》2022,13(21):6233
Modulation of N-glycosylation using human Golgi α-mannosidase II (α-hGMII) inhibitors is a potential anticancer approach, but the clinical utility of current α-hGMII inhibitors is limited by their co-inhibition of human lysosomal α-mannosidase (α-hLM), resulting in abnormal storage of oligomannoses. We describe the synthesis and screening of a small library of novel bicyclic iminosugar-based scaffolds, prepared via natural product-inspired combinatorial chemistry (NPICC), which resulted in the identification of a primary α-hGMII inhibitor with 13.5-fold selectivity over α-hLM. Derivatization of this primary inhibitor using computation-guided synthesis (CGS) yielded an advanced α-hGMII inhibitor with nanomolar potency and 106-fold selectivity over α-hLM. In vitro studies demonstrated its N-glycan modulation and inhibitory effect on hepatocellular carcinoma (HCC) cells. In vivo studies confirmed its encouraging anti-HCC activity, without evidence of oligomannose accumulation. An integrated strategy of Natural-Product-Inspired Combinatorial Chemistry (NPICC) and Computation-Guided Synthesis is used to develop an α-hGMII inhibitor with 106-fold selectivity over α-hLM, with inhibitory effect on hepatocellular carcinoma. 相似文献
16.
Xiangqing Jia Jrn Nitsch Zhu Wu Alexandra Friedrich Johannes Krebs Ivo Krummenacher Felipe Fantuzzi Holger Braunschweig Michael Moos Christoph Lambert Bernd Engels Todd B. Marder 《Chemical science》2021,12(35):11864
One-electron chemical reduction of 10-(dimesitylboryl)-N,N-di-p-tolylbenzo[c]phenanthrene-4-amine (3-B(Mes)2-[4]helix-9-N(p-Tol)2) 1 and 13-(dimesitylboryl)-N,N-di-p-tolyldibenzo[c,g]phenanthrene-8-amine (3-B(Mes)2-[5]helix-12-N(p-Tol)2) 2 gives rise to monoanions with extensive delocalization over the annulated helicene rings and the boron pz orbital. Two-electron chemical reduction of 1 and 2 produces open-shell biradicaloid dianions with temperature-dependent population of the triplet states due to small singlet-triplet gaps. These results have been confirmed by single-crystal X-ray diffraction, EPR and UV/vis-NIR spectroscopy, and DFT calculations.Stepwise chemical reduction of D–π–A triarylborane-based helicenes gives the corresponding monoanions and dianions with delocalized unpaired electrons. The structures were confirmed by single crystal X-ray diffraction. 相似文献
17.
Xin Wang Jiaxi Xu Zhenjiang Li Jingjing Liu Jie Sun Nikos Hadjichristidis Kai Guo 《Chemical science》2021,12(32):10732
The “coordination-insertion” ring-opening polymerization (ROP) mechanism has so far been the monopoly of metal catalysts. In this work, we present a metal-free “coordination-insertion” ROP of trimethylene carbonate (TMC) and ε-caprolactone (ε-CL), as well as their sequential block copolymerization, with N-trimethylsilyl-bis (trifluoromethanesulfonyl)imide (TMSNTf2) as the non-metallic initiator/catalyst. TMSNTf2 was proposed to work through an unprecedented metal-free “coordination-insertion” mechanism, which involves the coordination of monomer to the Si atom of TMSNTf2, the nucleophilic attack of the –NTf2 group on the coordinated monomer, and the cleavage of the acyl–oxygen bond of the monomer. The proposed metal-free “coordination-insertion” ROP was studied by NMR, SEC, and MALDI-TOF analyses. In addition, the TMSNTf2-mediated ROP of TMC and ε-CL led to linear and cyclic polymers following two-stage first-order polymerization processes, as evidenced by structural analyses and kinetics study, which further demonstrated the metal-free “coordination-insertion” mechanism.The first metal-free “coordination-insertion” ROP of cyclic carbonate and lactones mediated by N-trimethylsilyl-bis(trifluoromethanesulfonyl)imide (TMSNTf2) was proposed, which in the past was exclusively the monopoly of metal complex catalysts. 相似文献
18.
María Jesús Cabrera-Afonso Anasheh Sookezian Shorouk O. Badir Mirna El Khatib Gary A. Molander 《Chemical science》2021,12(26):9189
Alkene 1,2-dicarbofunctionalizations are highly sought-after transformations as they enable a rapid increase of molecular complexity in one synthetic step. Traditionally, these conjunctive couplings proceed through the intermediacy of alkylmetal species susceptible to deleterious pathways including β-hydride elimination and protodemetalation. Herein, an intermolecular 1,2-dicarbofunctionalization using alkyl N-(acyloxy)phthalimide redox-active esters as radical progenitors and organotrifluoroborates as carbon-centered nucleophiles is reported. This redox-neutral, multicomponent reaction is postulated to proceed through photochemical radical/polar crossover to afford a key carbocation species that undergoes subsequent trapping with organoboron nucleophiles to accomplish the carboallylation, carboalkenylation, carboalkynylation, and carboarylation of alkenes with regio- and chemoselective control. The mechanistic intricacies of this difunctionalization were elucidated through Stern–Volmer quenching studies, photochemical quantum yield measurements, and trapping experiments of radical and ionic intermediates.Alkene 1,2-dicarbofunctionalizations increase molecular complexity. Herein, the carboallylation, carboalkenylation, carboalkynylation, and carboarylation of olefins is accomplished through radical/polar crossover with organotrifluoroborates. 相似文献
19.
Jinsun Lee Xinghui Liu Ashwani Kumar Yosep Hwang Eunji Lee Jianmin Yu Young Dok Kim Hyoyoung Lee 《Chemical science》2021,12(28):9619
Photocatalytic N2 fixation to NH3via defect creation on TiO2 to activate ultra-stable N N has drawn enormous scientific attention, but poor selectivity and low yield rate are the major bottlenecks. Additionally, whether N2 preferentially adsorbs on phase-selective defect sites on TiO2 in correlation with appropriate band alignment has yet to be explored. Herein, theoretical predictions reveal that the defect sites on disordered anatase (Ad) preferentially exhibit higher N2 adsorption ability with a reduced energy barrier for a potential-determining-step (*N2 to NNH*) than the disordered rutile (Rd) phase of TiO2. Motivated by theoretical simulations, we synthesize a phase-selective disordered-anatase/ordered-rutile TiO2 photocatalyst (Na-Ad/Ro) by sodium-amine treatment of P25-TiO2 under ambient conditions, which exhibits an efficient NH3 formation rate of 432 μmol g−1 h−1, which is superior to that of any other defect-rich disordered TiO2 under solar illumination with a high apparent quantum efficiency of 13.6% at 340 nm. The multi-synergistic effects including selective N2 chemisorption on the defect sites of Na-Ad with enhanced visible-light absorption, suitable band alignment, and rapid interfacial charge separation with Ro enable substantially enhanced N2 fixation.This work highlights the importance of a rational design for more energetically suitable nitrogen reduction reaction routes and mechanisms by regulating the electronic band structures with phase-selective defect sites. 相似文献