Dr. Sung Beom Cho  Dr. Cheng He  Dr. Shrihari Sankarasubramanian  Arashdeep Singh Thind  Dr. Javier Parrondo  Dr. Jordan A. Hachtel  Dr. Albina Y. Borisevich  Dr. Juan-Carlos Idrobo  Jing Xie  Prof. Vijay Ramani  Prof. Rohan Mishra 《ChemSusChem》2021,14(21):4613-4614

Invited for this month′s cover are the groups of Prof. Vijay Ramani and Prof. Rohan Mishra at Washington University in St. Louis and their collaborators at Oak Ridge National Laboratory. The Full Paper itself is available at 10.1002/cssc.202101341 .  相似文献   

    

Dr. Mengci He  Prof. Hongyan Shi  Prof. Xiudong Sun  Prof. Bo Gao 《ChemCatChem》2021,13(3):966-974

Heterogeneous structure composed of different active materials is an important strategy to improve the HER performance of catalysts, due to the synergistic effects on the interface. Here, we synthesized a Mo₂C−MoP heterostructure by phosphating porous β-Mo₂C nanostructures with red phosphorus powder. XRD, Raman, XPS, SEM and TEM results suggested that Mo₂C−MoP heterostructure with porous nanostructures were obtained on carbon cloth at 550 °C (MoCP-550), which showed remarkable HER activity over a broad pH range. A low η₁₀ of 51 mV and a small Tafel slope of 56.7 mV dec⁻¹ was achieved in 1.0 M KOH, and a low η₁₀ of 82 mV and a small Tafel slope of 49.8 mV dec⁻¹ in 0.5 M H₂SO₄. MoCP-550 also exhibited excellent electrocatalytic stability in both alkaline and acidic electrolytes. Density functional theory (DFT) calculations identified that Mo₂C−MoP heterostructure has more suitable H^* adsorption free energy compared to pure Mo₂C and pure MoP.  相似文献   

    

Dr. Xiao-Long He  Cheng Wang  You-Wu Wen  Prof. Zhouyu Wang  Prof. Shan Qian 《ChemCatChem》2021,13(16):3547-3564

Pentatomic heterobiaryl performs as a key structural motif in various natural products and bioactive compounds. With the rapid growth of asymmetric catalysis, five-membered heterobiaryl-based catalysts and ligands have emerged as an efficient complementary toolbox for asymmetric catalysis. Therefore, the development of enantioselective construction of such pentatomic atropisomers has received significant attention in recent decade. Various catalytic asymmetric strategies have been established, including central to axial chirality conversion, direct generation of heteroaryl, direct assembly of aryl-heteroaryls, functionalization of racemic or prochiral biaryls, and chirality transfer from atropisomeric alkenes. Hundreds of unprecedented pentatomic atropisomers have proliferated. Importantly, a few promising axially chiral catalysts and ligands have been obtained from the prepared heterobiaryls after simple transformations. Hence, recent advances of catalytic asymmetric construction of axially chiral pentatomic heterobiaryls through asymmetric catalysis are summarized in this review, involving their scope, mechanism, transformations, and applications.  相似文献   

    

Susana Guadix-Montero  Alba Santos Hernandez  Nian Lei  David J. Morgan  Qian He  Aiqin Wang  Tao Zhang  Dr. Alberto Roldan  Dr. Meenakshisundaram Sankar 《ChemCatChem》2021,13(6):1595-1606

Controlling the selectivity of a reaction by rational designing of catalyst is an important and challenging topic in catalysis research. In this article, we report a strategy to tune the product selectivity during aqueous phase hydrogenolysis of glycerol using gaseous H₂. Ru/TiO₂ is an active catalyst for the hydrogenolysis of glycerol, however it promotes the hydrogenolysis of C−C bonds resulting in large quantities of C2 and C1 products. On the other hand, Pd/TiO₂ and Pt/TiO₂ catalysts are very selective for the hydrogenolysis of C−O bonds producing mainly C3 products (1,2 and 1,3 propanediols), however they are much less active compared to the Ru catalysts. In this article, we report that by combining Ru with Pt or Pd in a bimetallic nanoparticle, we can develop new catalysts that are both active and selective for C−O hydrogenolysis. A physical mixture of two monometallic catalysts does not show this enhanced selectivity for C−O hydrogenolysis, proving that intimate mixing of the two metals in a nanoparticle is crucial to tune the selectivity. All the monometallic and bimetallic catalysts have been characterised by microscopic and spectroscopic methods to understand their structural features. DFT studies were also done to rationalise the observed difference in the catalytic properties between monometallic and bimetallic catalysts.  相似文献   

    

Xinyu Wang  Zhongyu He  Dr. Xin Xu  Haoqiang Zhao  Dr. Yixiao Pan  Prof. Huanrong Li  Prof. Lijin Xu 《ChemCatChem》2021,13(7):1730-1737

Chelation-assisted C6-selective acylmethylation and carboxymethylation of 2-pyridones with diazo carbonyl compounds under [Cp*RhCl₂]₂/AgSbF₆ catalysis have been developed. Deesterificative C6-acylmethylation of 2-pyridones with diazo tert-butyl ester compounds proceeds effectively with the use of HOAc additive and hexafluoroisopropanol (HFIP) solvent, whereas switching to NaOAc additive and MeOH solvent enables efficient deacylative C6-carboxymethylation of 2-pyridones with alkyl 2-diazo-3-oxobutanoates. The procedures are characterized by excellent regioselectivity, high efficiency, broad substrate scope, wide functional group compatibility and gram-scalability. Preliminary mechanistic experiments are conducted to gain insights into the reaction mechanisms.  相似文献   

    

Binbin Zhao  Yu Liang  Prof. Lei Liu  Prof. Qian He  Prof. Jin-Xiang Dong 《ChemCatChem》2021,13(16):3695-3705

Designing efficient catalysts for glycerol hydrogenolysis to 1,3-propanediol (1,3-PDO), which involves the selective cleavage of the secondary C−O bond, is a challenging task. Current Pt−WO_x-based catalysts often provide low atom efficiency of W and Pt toward 1,3-PDO production due to undesired catalyst structures. Herein, we fabricate the highly-dispersed substantially uniform WO_x species on inert α-Al₂O₃ support by simple high-temperature heat-treatment, and the amount of Pt−WO_x interface active sites could be adjusted by Pt loading, showing an excellent catalytic performance in glycerol hydrogenolysis at high concentration of glycerol, especially the unprecedented W efficiency (76 g_1,3-PDOg_W⁻¹ h⁻¹) toward 1,3-PDO. The high catalytic efficiency is attributed to the strong interaction between the isolated WO₄ species and platinum, which could in-situ generate the Brønsted acid sites during the reaction as evidenced by IR analysis with NH₃ adsorption.  相似文献   

    

Dong-Dong Zhou  Jun Wang  Pin Chen  Yangyong He  Jun-Xi Wu  Sen Gao  Zhihao Zhong  Yunfei Du  Dingyong Zhong  Jie-Peng Zhang 《Chemical science》2021,12(4):1272

Rational manipulation of supramolecular structures on surfaces is of great importance and challenging. We show that imidazole-based hydrogen-bonded networks on a metal surface can transform into an isostructural coordination network for facile tuning of the pore size and guest recognition behaviours. Deposition of triangular-shaped benzotrisimidazole (H₃btim) molecules on Au(111)/Ag(111) surfaces gives honeycomb networks linked by double N–H⋯N hydrogen bonds. While the H₃btim hydrogen-bonded networks on Au(111) evaporate above 453 K, those on Ag(111) transform into isostructural [Ag₃(btim)] coordination networks based on double N–Ag–N bonds at 423 K, by virtue of the unconventional metal–acid replacement reaction (Ag reduces H⁺). The transformation expands the pore diameter of the honeycomb networks from 3.8 Å to 6.9 Å, giving remarkably different host–guest recognition behaviours for fullerene and ferrocene molecules based on the size compatibility mechanism.

A hydrogen-bonded network on a Ag(111) surface can transform into an isostructural Ag(i) coordination network, giving drastically different host–guest recognition behaviours.  相似文献   

    

Jing Li  Huayi Shi  Runzhi Chen  Xiaofeng Wu  Jiayi Cheng  Fenglin Dong  Houyu Wang  Yao He 《Chemical science》2021,12(3):896

Synthesis of programmable atom-like nanoparticles (PANs) with high valences and high yields remains a grand challenge. Here, a novel synthetic strategy of microfluidic galvanic displacement (μ-GD) coupled with microfluidic DNA nanoassembly is advanced for synthesis of single-stranded DNA encoder (SSE)-encoded PANs for reliable surface-enhanced Raman scattering (SERS) sensing. Notably, PANs with high valences (e.g., n-valence, n = 12) are synthesized with high yields (e.g., >80%) owing to the effective control of interfacial reactions sequentially occurring in the microfluidic system. On the basis of this, we present the first demonstration of a PAN-based automatic analytical platform, in which sensor construction, sample loading and on-line monitoring are carried out in the microfluidic system, thus guaranteeing reliable quantitative measurement. In the proof-of-concept demonstration, accurate determination of tetracycline (TET) in serum and milk samples with a high recovery close to 100% and a low relative standard deviation (RSD) less than 5.0% is achieved by using this integrated analytical platform.

A novel synthetic strategy is presented for microfluidic preparation of programmable atom-like nanoparticles with high valences and high yields.  相似文献   

    

Hongzhi Qiao  Lei Zhang  Dong Fang  Zhenzhu Zhu  Weijiang He  Lihong Hu  Liuqing Di  Zijian Guo  Xiaoyong Wang 《Chemical science》2021,12(12):4547

Copper complexes are promising anticancer agents widely studied to overcome tumor resistance to metal-based anticancer drugs. Nevertheless, copper complexes per se encounter drug resistance from time to time. Adenosine-5′-triphosphate (ATP)-responsive nanoparticles containing a copper complex CTND and B-cell lymphoma 2 (Bcl-2) small interfering RNA (siRNA) were constructed to cope with the resistance of cancer cells to the complex. CTND and siRNA can be released from the nanoparticles in cancer cells upon reacting with intracellular ATP. The resistance of B16F10 melanoma cells to CTND was terminated by silencing the cellular Bcl-2 gene via RNA interference, and the therapeutic efficacy was significantly enhanced. The nanoparticles triggered a cellular autophagy that amplified the apoptotic signals, thus revealing a novel mechanism for antagonizing the resistance of copper complexes. In view of the extensive association of Bcl-2 protein with cancer resistance to chemotherapeutics, this strategy may be universally applicable for overcoming the ubiquitous drug resistance to metallodrugs.

Bcl-2-related tumor resistance to anticancer drugs can be overcome by silencing the cellular Bcl-2 gene via RNA interference. The realization of the goal is exemplified by delivering Bcl-2 siRNA and a tumor-resistant Cu complex to cancer cells with an ATP-responsive nanocarrier.  相似文献   

    

Xiao-Long Lu  Yuanyou Qiu  Baochao Yang  Haibing He  Shuanhu Gao 《Chemical science》2021,12(13):4747

The asymmetric total synthesis of (+)-xestoquinone and (+)-adociaquinones A and B was achieved in 6–7 steps using an easily accessible meso-cyclohexadienone derivative. The [6,6]-bicyclic decalin B–C ring and the all-carbon quaternary stereocenter at C-6 were prepared via a desymmetric intramolecular Michael reaction with up to 97% ee. The naphthalene diol D–E ring was constructed through a sequence of Ti(Oi-Pr)₄-promoted photoenolization/Diels–Alder, dehydration, and aromatization reactions. This asymmetric strategy provides a scalable route to prepare target molecules and their derivatives for further biological studies.

The asymmetric total synthesis of (+)-xestoquinone and (+)-adociaquinones A and B was achieved in 6–7 steps using an easily accessible meso-cyclohexadienone derivative.

Various halenaquinone-type natural products with promising biological activity have been isolated from marine sponges of the genus Xestospongia¹ from the Pacific Ocean. (+)-Halenaquinone (1),^2,3 (+)-xestoquinone (2), and (+)-adociaquinones A (3) and B (4)^4,5 bearing a naphtha[1,8-bc]furan core (Fig. 1) are the most typical representatives of this family. Naturally occurring (−)-xestosaprol N (5) and O (6)^6,7 have the same structure as 3 and 4 except for a furan ring, while a naphtha[1,8-bc]furan core can also be found in fungus-isolated furanosteroids (−)-viridin (7) and (+)-nodulisporiviridin E (8)^8,9 (Fig. 1). Halenaquinone (1) was first isolated from the tropical marine sponge Xestospongia exigua² and it shows antibiotic activity against Staphylococcus aureus and Bacillus subtilis. Xestoquinone (2) and adociaquinones A (3) and B (4) were firstly isolated, respectively, from the Okinawan marine sponge Xestospongia sp.^4a and the Truk Lagoon sponge Adocia sp.,^4b and they show cardiotonic,^4a,c cytotoxic,^4b,i antifungal,⁴ⁱ antimalarial,^4j and antitumor^4l activities. These compounds inhibit the activity of pp60v-src protein tyrosine kinase,^4d topoisomerases I^4e and II,^4f myosin Ca²⁺ ATPase,^4c,g and phosphatases Cdc25B, MKP-1, and MKP-3.^4h,kOpen in a separate windowFig. 1Structure of halenaquinone-type natural products and viridin-type furanosteroids.Owing to their diverse bioactivities, the synthesis of this family of natural compounds has been extensively studied, with published pathways making use of Diels–Alder,^{3a,d,e,5a–c,e,g} furan ring transfer,^5b Heck,^{3b,c,5f,7,9b,d} palladium-catalyzed polyene cyclization,^5d Pd-catalyzed oxidative cyclization,^3f and hydrogen atom transfer (HAT) radical cyclization^9c reactions. In this study, we report the asymmetric total synthesis of (+)-xestoquinone (2), (−)-xestoquinone (2′), and (+)-adociaquinones A (3) and B (4) (Fig. 1).The construction of the fused tetracyclic B–C–D–E skeleton and the all carbon quaternary stereocenter at C-6 is a major challenge towards the total synthesis of xestoquinone (2) and adociaquinones A (3) and B (4). Based on our retrosynthetic analysis (Scheme 1), the all-carbon quaternary carbon center at C-6 of cis-decalin 12 could first be prepared stereoselectively from the achiral aldehyde 13via an organocatalytic desymmetric intramolecular Michael reaction.^10,11 The tetracyclic framework 10 could then be formed via a Ti(Oi-Pr)₄-promoted photoenolization/Diels–Alder (PEDA) reaction^12–16 of 11 and enone 12. Acid-mediated cyclization of 10 followed by oxidation state adjustment could be subsequently applied to form the furan ring A of xestoquinone (2). Finally, based on the biosynthetic pathway of (+)-xestoquinone (2)^4b,5c and our previous studies,⁷ the heterocyclic ring F of adociaquinones A (3) and B (4) could be prepared from 2via a late-stage cyclization with hypotaurine (9).Open in a separate windowScheme 1Retrosynthetic analysis of (+)-xestoquinone and (+)-adociaquinones A and B.The catalytic enantioselective desymmetrization of meso compounds has been used as a powerful strategy to generate enantioenriched molecules bearing all-carbon quaternary stereocenters.^10,11 For instance, two types of asymmetric intramolecular Michael reactions were developed using a cysteine-derived chiral amine as an organocatalyst by Hayashi and co-workers,^11a,b while a desymmetrizing secondary amine-catalyzed asymmetric intramolecular Michael addition was later reported by Gaunt and co-workers to produce enantioenriched decalin structures.^11c Prompted by these pioneering studies and following the suggested retrosynthetic pathway (Scheme 1), we first screened conditions for organocatalytic desymmetric intramolecular Michael addition of meso-cyclohexadienone 13 (Table 1) in order to form the desired quaternary stereocenter at C-6. Compound 13 was easily prepared on a gram scale via a four-step process (see details in the ESI^†).Attempts of organocatalytic desymmetric intramolecular Michael addition^a

Entry	Cat. (equiv.)	Additive (equiv.)	Solvent	Time	Yield/d.r. at C2b	e.e.c
1	(R)-cat.I (0.5)	—	Toluene	10.0 h	52%/10.3 : 1	14a: 96%; 14b: 75%
2	(R)-cat.I (1.0)	—	Toluene	4.0 h	60%/10.0 : 1	14a: 93%; 14b: 75%
3	(R)-cat.I (1.0)	—	MeOH	4.0 h	47%/5.5 : 1	14a: 86%; 14b: −3%
4	(R)-cat.I (1.0)	—	DCM	10.0 h	28%/24.0 : 1	14a: 91%; 14b: 7%
5	(R)-cat.I (1.0)	—	Et2O	10.0 h	22%/22.0 : 1	14a: 91%; 14b: 65%
6	(R)-cat.I (1.0)	—	MeCN	10.0 h	12%/2.6 : 1	14a: 90%; 14b: 62%
7	(R)-cat.I (1.0)	—	Toluene/MeOH (2 : 1)	4.0 h	47%/10.0 : 1	14a: 87%; 14b: −38%
8d	(R)-cat.I (1.0)	AcOH (5.0)	Toluene	4.0 h	60%e/2.1 : 1	14a: 96%; 14b: 95%
9d	(R)-cat.I (0.5)	AcOH (2.0)	Toluene	6.0 h	75%e/4.0 : 1	14a: 97%; 14b: 91%
10d	(R)-cat.I (0.5)	AcOH (0.2)	Toluene	6.0 h	73%e/4.3 : 1	14a: 96%; 14b: 92%
11f	(R)-cat.I (0.5)	AcOH (0.2)	Toluene	6.0 h	75%e/8.0 : 1g	14a: 95%; 14b: 93%
12h	(R)-cat.I (0.2)	AcOH (0.2)	Toluene	9.0 h	80%i/6.0 : 1j	14a: 97%; 14b: 91%

Open in a separate window^aAll reactions were performed using 13 (5.8 mg, 0.03 mmol, 1.0 equiv., and 0.1 M) and a catalyst at room temperature in analytical-grade solvents, unless otherwise noted.^bThe yields and diastereoisomeric ratios (d.r.) were determined from the crude ¹H NMR spectrum of 14 using CH₂Br₂ as an internal standard, unless otherwise noted.^cThe enantiomeric excess (e.e.) values were determined by chiral high-performance liquid chromatography (Chiralpak IG-H).^dCompound 13: 9.6 mg, 0.05 mmol, and 0.1 M.^eIsolated combined yield of 14a + 14b.^fCompound 13: 192 mg, 1.0 mmol, and 0.1 M.^gThe d.r. values decreased to 1 : 1 after purification by silica gel column chromatography.^hCompound 13: 1.31 g, 6.82 mmol, and 0.1 M.ⁱIsolated combined yield of 12a + 12b.^jThe d.r. values were determined from the crude ¹H NMR spectrum of 12 obtained from the one-pot process.We initially investigated the desymmetric intramolecular Michael addition of 13 using (S)-Hayashi–Jørgensen catalysts,¹⁷ and found that the absolute configuration of the obtained cis-decalin was opposite to the required stereochemistry of the natural products (see Table S1 in the ESI^†). In order to achieve the desired absolute configuration of the angular methyl group at C-6, (R)-cat.I was used for further screening. In the presence of this catalyst, the intramolecular Michael addition afforded 14a (96% e.e.) and 14b (75% e.e.) in a ratio of 10.3 : 1 and 52% combined yield (entry 1, Table 1). We assumed that the enantioselectivity of the reaction was controlled by the more sterically hindered aromatic group of (R)-cat.I, which protected the upper enamine face and allowed an endo-like attack by the si-face of cyclohexadienone, as shown in the transition state TS-A (Table 1). In order to increase the yield of this reaction and improve the enantioselectivity of 14b, we further screened solvents and additives. Increasing the catalyst loading from 0.5 to 1.0 equivalents and screening various reaction solvents did not improve the enantiomeric excess of 14b (entries 2–7, Table 1). Therefore, based on previous studies,^11d,e we added 5.0 equivalents of acetic acid (AcOH) to a solution of compound 13 and (R)-cat.I in toluene, which improved the enantiomeric excess of 14b to 95% with a 60% combined yield (entry 8, Table 1). And, the stability of (R)-cat.I has also been verified in the presence of AcOH (see Table S2 in the ESI^†). Further adjustment of the (R)-cat.I and AcOH amount and ratio (entries 9–12, Table 1) indicated that 0.2 equivalents each of (R)-cat.I and AcOH were the best conditions to achieve high enantioselectivity for both 14a and 14b, and it also increased the reaction yield (entry 12, Table 1). The enantioselectivity was not affected when the optimized reaction was performed on a gram scale: 14a (97% e.e.) and 14b (91% e.e.) were obtained in 80% isolated yield (entry 12, Table 1). We also found that the gram-scale experiments needed a longer reaction time which led a slight decrease of the diastereoselectivity. The purification of the cyclized products by silica gel flash column chromatography indicated that the major product 14a was epimerized and slowly converted to the minor product 14b (entry 11, Table 1). Both 14a and 14b are useful in the syntheses because the stereogenic center at C-2 will be converted to sp² hybridized carbon in the following transformations. Therefore, the aldehyde group of analogues 14a and 14b was directly protected with 1,3-propanediol to give the respective enones 12a and 12b for use in the subsequent PEDA reaction.Afterward, we selected the major cyclized cis-decalins 12a and 12a′ (obtained by using (S)-cat.I in desymmetric intramolecular Michael addition, see Table S1 in the ESI^†) as the dienophiles to prepare the tetracyclic naphthalene framework 10 through a sequence of Ti(Oi-Pr)₄-promoted PEDA, dehydration, and aromatization reactions (Scheme 2). When using 3,6-dimethoxy-2-methylbenzaldehyde (11) as the precursor of diene, no reaction occurred between 12a/12a′ and 11 under UV irradiation at 366 nm in the absence of Ti(Oi-Pr)₄ (Scheme 2A). In contrast, the 1,2-dihydronaphthalene compounds 16a and 16a′ were successfully synthesized when 3.0 equivalents of Ti(Oi-Pr)₄ were used. Based on our previous studies,^13a,e the desired hydroanthracenol 15a was probably generated through the chelated intermediate TS-B and the cycloaddition occurred through an endo direction (Scheme 2B).¹⁸ The newly formed β-hydroxyl ketone groups in 15a and 15a′ could then be dehydrated with excess Ti(Oi-Pr)₄ to form enones 16a and 16a′. These results confirmed the pivotal role of Ti(Oi-Pr)₄ in this PEDA reaction: it stabilized the photoenolized hydroxy-o-quinodimethanes and controlled the diastereoselectivity of the reaction.Open in a separate windowScheme 2PEDA reaction of 11 and enone 12.Subsequent aromatization of compounds 16a and 16a′ with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) at 80 °C afforded compounds 10a and 10a′ bearing a fused tetracyclic B–C–D–E skeleton. The stereochemistry and absolute configuration of 10a were confirmed by X-ray diffraction analysis of single crystals (Scheme 3). The synthesis of (+)-xestoquinone (2) and (+)-adociaquinones A (3) and B (4) was completed by forming the furan A ring. Compound 10 was oxidized using bubbling oxygen gas in the presence of t-BuOK to give the unstable diosphenol 17a, which was used without purification in the next step. The subsequent acid-promoted deprotection of the acetal group led to the formation of an aldehyde group, which reacted in situ with enol to furnish the pentacyclic compound 18 bearing the furan A ring. The stereochemistry and absolute configuration of 18 were confirmed by X-ray diffraction analysis of single crystals (Scheme 3). Further oxidation of 18 with ceric ammonium nitrate afforded (+)-xestoquinone (2) in 82% yield. Following the same reaction process, (−)-xestoquinone (2′) was also synthesized from 10a′ in order to determine in the future whether xestoquinone enantiomers differ in biological activity. Further heating of a solution of (+)-xestoquinone (2) with hypotaurine (9) at 50 °C afforded a mixture of (+)-adociaquinones A (3) (21% yield) and B (4) (63% yield). We also tried to optimize the selectivity of this condensation by tuning the reaction temperature and pH of reaction mixtures (see Table S3 in the ESI^†). The ¹H and ¹³C NMR spectra, high-resolution mass spectrum, and optical rotation of synthetic (+)-xestoquinone (2), (+)-adociaquinones A (3) and B (4) were consistent with those data reported by Nakamura,^4a,g Laurent,^4j Schmitz,^4b Harada^5a,c and Keay.^5dOpen in a separate windowScheme 3Total synthesis of (+)-xestoquinone and (+)-adociaquinones A and B.  相似文献