Effects of indium on Ni/SiO_2 catalytic performance in hydrodeoxygenation of anisole as model bio-oil compound: Suppression of benzene ring hydrogenation and C–C bond hydrogenolysis

SiO2‐supported monometallic Ni and bimetallic Ni‐In catalysts were prepared and used for hydrodeoxygenation of anisole,which was used as a model bio‐oil compound,for BTX(benzene,toluene,and xylene)production.The effects of the Ni/In ratio and Ni content on the structures and performances of the catalysts were investigated.The results show that In atoms were incorporated into the Ni metal lattice.Although the Ni‐In bimetallic crystallites were similar in size to those of monometallic Ni at the same Ni content,H2uptake by the bimetallic Ni‐In catalyst was much lower than that by monometallic Ni because of dilution of Ni atoms by In atoms.Charge transfer from In to Ni was observed for the bimetallic Ni‐In catalysts.All the results indicate intimate contact between Ni and In atoms,and the In atoms geometrically and electronically modified the Ni atoms.In the hydrodeoxygenation of anisole,although the activities of the Ni‐In bimetallic catalysts in the conversion of anisole were lower than that of the monometallic Ni catalyst,they gave higher selectivities for BTX and cyclohexane as a result of suppression of benzene ring hydrogenation and C–C bond hydrogenolysis.They also showed lower methanation activity.These results will be useful for enhancing carbon yields and reducing H2consumption.In addition,the lower the Ni/In ratio was,the greater was the effect of In on the catalytic performance.The selectivity for BTX was primarily determined by the Ni/In ratio and was little affected by the Ni content.We suggest that the performance of the Ni‐In bimetallic catalyst can be ascribed to the geometric and electronic effects of In.

Catalytic transformation of cellulose and its derived carbohydrates into chemicals involving C–C bond cleavage

The catalytic transformation of cellulose, the major component of abundant and renewable lignocellulosic biomass, into building-block chemicals is a key to establishing sustainable chemical processes. Cellulose is a polymer of glucose and a lot research effort has been devoted to the conversion of cellulose to six-carbon platform compounds such as glucose and glucose derivatives through C-O bond activation. There also ex- ist considerable studies on the catalytic cleavage of C-C bonds in biomass for the production of high-value chemicals, in particular polyols and organic acids such as ethylene glycol and lactic acid. This review article highlights recent advances in the development of new catalytic systems and new strategies for the selective cleavage of C-C bonds in cellulose and its derived carbohydrates under inert, reductive and oxidative atmospheres to produce Q -Cs polyols and organic acids. The key factors that influence the catalytic performance will be clarified to provide insights for the design of more efficient catalysts for the transformation of cellulose with precise cleavage of C-C bonds to high-value chemicals. The reaction mechanisms will also be discussed to understand deeply how the selective cleavage of C-C bonds can be achieved in biomass.

Enhancement of CH_(3)CO^(*) adsorption by editing d-orbital states of Pd to boost C–C bond cleavage of ethanol eletrooxidation

Improving the complete ethanol electrooxidation on Pd-based catalysts in alkaline media has drawn widely attention due to the high mass energy density.However,the weak adsorption energy of CH_(3)CO^(*) on Pd restricts the C–C bond cleavage.Inspired by the molecular orbital theory,we proposed the d-state-editing strategy to construct more unoccupied d-states of Pd for the enhanced interaction with CH_(3)CO^(*) to break C–C bonds.As expected,the reduced number of e_g electrons and more unoccupied d-states of Pd successfully formed on as-prepared porous Rh Au–Pd Cu nanosheets(PNSs).Theoretical calculations show that the optimized d-states of Rh Au–Pd Cu PNS can effectively improve the adsorption of CH_(3)CO^(*) and drastically reduce the energy barrier of C–C bond cleavage,thus boosting the complete oxidation of ethanol.The charge ratio of C_1 pathway on Rh Au–Pd Cu PNSs is 51.5%,more than 2 times higher than that of Pd NSs.Our finding provides an innovative perspective for the design of highly-efficient noble-based electrocatalysts.

钯催化Heck反应研究进展

Heck反应是一类构建新的C-C键的重要合成方法,近年来随着新的高活性配体的发展,Heck反应取得了突破性的进展,一些结构复杂以及具有两个手性中心的杂环化合物被高选择性地合成,这一反应成功地应用于合成复杂天然产物和药物分子。从分子内和分子间两方面综述了十几年来钯催化的Heck反应,同时对该领域未来的发展作出了展望。

过渡金属参与切断苄位C—H键构建C—C键

过渡金属参与切断苄位C—H键构建C—C键是有机合成化学的研究热点之一。该领域具有广阔的应用前景和发展潜力,可应用于中间体的合成、医药和农药等领域。综述了过渡金属参与切断苄位C—H键构建C—C键的研究进展。

Ni-catalyzed carbon–carbon bonds cleavage of mixed polyolefin plastics waste

The inert carbon–carbon(C–C) bonds cleavage is a main bottleneck in the chemical upcycling of recalcitrant polyolefin plastics waste. Here we develop an efficient strategy to catalyze the complete cleavage of C–C bonds in mixed polyolefin plastics over non-noble metal catalysts under mild conditions. The nickelbased catalyst involving Ni_(2)Al_(3) phase enables the direct transformation of mixed polyolefin plastics into natural gas, and the gas carbon yield reaches up to 89.6%. Reaction pathway investigation reveals that natural gas comes from the stepwise catalytic cleavage of C–C bonds in polypropylene, and the catalyst prefers catalytic cleavage of terminal C–C bond in the side-chain with the low energy barrier.Additionally, our developed approach is evaluated by the technical economic analysis for an economically competitive production process.

Amides as surrogates of aldehydes for C–C bond formation:amide-based direct Knoevenagel-type condensation reaction and related reactions

Aldehydes are perhaps the most versatile compounds that enable many C-C bond forming reactions,which are not amenable for other subclasses of carbonyl compounds.We report the first use of amides as surrogates of aldehydes for C-C bond formation,namely,the direct Knoevenagel-type condensation based on amides.The one-pot method consists of controlled reduction of an amide with LDBIPA[LiAlH(iBu)2(OiPr)],Lewis acid-mediated release of a reactive iminium ion intermediate,nucleophilic addition,and in situ elimination of amine.The reaction shows good functional group tolerance.We also demonstrated that the Schwartz reagent could be used as an alternative of LDBIPA.The employment of nitromethane and a silyl enol ether as the nucleophiles opens an avenue for the unprecedented amide-based nitro-aldol condensation reaction and aldol condensation reaction,respectively.

Regiodivergent Access to 2- or 3-Substituted Indanones: Catalyst-Controlled Carboacylation via C–C Bond Activation

Indanones are ubiquitous in biologically active compounds.Intramolecular hydroacylation of aldehydes and alkenes is an efficient and atomeconomic route to indane rings.However,these reactions are limited to the transfer of a hydride to the alkene.The transfer of aryl groups enabling the formation of C–C bonds during the cyclization would be a new method for the synthesis of substituted indanones.This report describes the regiodivergent carboacylation of alkenes with ketones to furnish both 2-and 3-substituted indanones in a regiocontrolled manner.

Electrochemical Ring Expansion to Synthesize Medium-Sized Lactams Through C–C Bond Cleavage

Medium-sized nitrogen heterocycles are prevalent motifs in many kinds of bioactive molecules and natural products.Owing to the unfavorable enthalpic and entropic barriers during the transition states,access to medium-sized rings is challenging.Herein,a general and practical electrochemical ringexpansion protocol has been developed from commercially available benzocyclic ketones and amides.In this regard,a series of highly functionalized eightto eleven-membered lactams could be successfully accessed in high yields and efficiencies.

可见光催化CO_(2)参与的芳基烯烃碳碳双键断键羧基化反应

烯烃广泛存在于自然界中,在医药、农药和材料等领域具有重要应用.烯烃的C=C键断裂和转化是许多工业过程的基础,可以实现烃类资源的重组与利用.目前,C=C键参与的氧化裂解和烯烃复分解反应已有广泛的研究.相比而言,C=C键参与的还原裂解虽然是烯烃与一系列亲电试剂反应合成功能分子的重要途径,但受限于烯烃自身结构和反应特点,该过程存在较大的挑战,目前研究很少.CO_(2)具有储量丰富、廉价易得、无毒且可循环再生等优点,是合成多种大宗化学品及精细化学品的理想碳一资源.然而,CO_(2)由于热力学稳定性及动力学惰性,在温和条件下难以高效、高选择性转化.因此,利用CO_(2)参与烯烃C=C键还原裂解,选择性构建高值化合物,是一个重要且具有挑战性的研究方向.近年来,可见光催化由于具有反应条件温和、官能团兼容性高等优点,为有机合成等领域提供了新的发展机遇.本文利用二环己基甲基胺作为电子给体,成功实现了可见光催化CO_(2)参与的芳基烯烃C=C键断键羧基化反应.该反应成功的关键在于,二环己基甲基胺既能高效还原淬灭激发态光敏剂并参与烯烃的胺基烷基-羧基化反应,又不明显抑制胺基烷基化中间体对激发态光敏剂的还原淬灭.研究结果表明,多种不同取代(如给电子基和吸电子基)的芳基烯烃均可与CO_(2)发生羧基化反应,高效高选择性地构建了一系列官能团丰富的芳基乙酸类化合物(如萘普生等药物分子).该方法具有反应条件温和(1 atm,室温)、官能团耐受性好以及可用于合成药物衍生物等特点.此外,本文通过氘代实验等机理研究和密度泛函理论计算证明,胺甲基羧化中间体、苄基自由基和苄基碳负离子都是该反应的关键中间体,并提出了可能的反应机理:首先,二环己基甲基胺还原淬灭激发态光敏剂,产生α-胺基碳自由基,与芳基烯烃发生自由基加成反应,得到苄基自由基,进而被还原态光敏剂还原为碳负离子,对CO_(2)亲核进攻得到烯烃的胺基烷基-羧基化中间体;作为电子给体,该中间体可以淬灭另一分子的激发态光敏剂,并通过分子内去质子化过程,产生α-胺基碳自由基物种,进而经历自由基型β-C断裂,生成热力学更稳定的羧基化苄基自由基,从而实现了烯烃C=C键的还原裂解;最后,新产生的苄基自由基被进一步还原为碳负离子,经历质子化过程后得到目标产物.综上,本文以还原裂解的方式丰富了C=C键断键官能团化反应领域,在温和条件下实现了CO_(2)的高效高选择性转化,合成了高附加值的芳基乙酸类化合物,阐明了反应机制,为烯烃和CO_(2)的同时高值化利用提供了新思路,为后续相关反应的开发和应用提供参考.

在过渡金属催化剂上的C―C键断裂以实现生物质的升级

将当前能源生产和消费结构从过度依赖化石能源转变为高效利用可再生能源,是解决能源危机、实现碳中和的有效途径。生物质是最有前途的可再生能源之一,可以取代化石燃料以获得有价值的有机化合物。近年来,大力利用生物质能已成为一种必然趋势。用于生物质转化的传统热化学催化方法通常需要高温、高压等恶劣条件,甚至还需要外部氢或氧源。相比之下,在相对温和的条件下进行的生物质有机分子电催化转化为生产高价值化学品提供了一种绿色高效的策略。特别是,通过C―C键裂解将生物质衍生的分子转化为高价值的短链化学品至关重要。近年来,大量的研究证明过渡金属(TM)电催化剂由于其丰富的三维电子结构和独特的eg轨道增强了过渡金属-氧之间的共价键合,从而在有机物的C―C键断裂中起着至关重要的作用。此外,TM电催化剂的配位环境或电子结构会影响产物的选择性。毫无疑问,明确的反应活性位点和途径有助于深入理解催化剂结构与反应活性之间的构效关系。然而,TM电催化剂介导的生物质衍生有机分子的C―C键裂解反应用于生物质升级的研究目前尚处于起步阶段,其反应机理和催化反应过程尚不清楚。因此,有必要在原子水平上系统地了解电催化剂在C―C键裂解过程中的作用。在本综述中,我们首先依次介绍了广泛研究的TM电催化剂介导的生物质衍生有机分子(包括甘油、环己醇、木质素和糠醛)的C―C键裂解反应,并给出了一些典型的例子和相应的反应途径。然后,系统回顾了过渡金属化合物催化C―C键裂解的反应机理,揭示了界面行为,并构建了TM电催化剂的结构与裂解反应活性之间的构效关系。最后,我们简要总结了上述内容,并强调了在TM电催化剂上研究C―C键裂解的挑战和展望。我们期望这项工作可以为生物质的可控转化和合理设计C―C键裂解的TM电催化剂提供指导。

蓝光诱导苯基重氮乙酸酯与1,3-二酮的C-C键插入反应

卡宾是有机合成中的一类重要的活性中间体,可发生丰富的化学转化,在C-C键、C-H键、C-N键、C-O键和C-S键等构建中有重要应用。采用重氮化合物为卡宾前驱原料,在蓝光诱导下与1,3-二羰基化合物进行反应,合成了全碳季碳中心的1,4-二羰基产物。该方法的特点是不使用金属催化剂、有良好的产率和选择性、操作简单、绿色环保无污染。

Redox-neutral photocatalytic strategy for selective C–C bond cleavage of lignin and lignin models via PCET process

It remains challenging to achieve the selective cleavage of C–C bonds in lignin or lignin model compounds to produce aromatic products in high yield and selectivity.We have developed a redox-neutral photocatalytic strategy to accomplish this goal in both b-O-4 and b-1 lignin models at room temperature(RT)via proton-coupled electron transfer(PCET)process without any pretreatments of substrate,by adjusting the alkalinity of base to obtain a lignin models/base PCET pair with a bond dissociation free energy close to 102 kcal/mol.Without breaking down C_b–Ccbond and any C–O bonds,this PCET method is 100%atom economy and produces exclusive Ca–C_bbond cleavage products,such as benzaldehydes(up to 97%)and phenyl ethers(up to 96%),in high to excellent yields and selectivities.Preliminary studies indicated that the PCET strategy is also effective for the depolymerization of native lignin at RT,thus providing significantly important foundation to the depolymerization of lignin.

Radical cascade reactions of unsaturated C–C bonds involving migration

During the past few years, with the rapid development of mild methods for the generation of radical species, great progress in radical cascade reactions of unsaturated C–C bonds has been made. Many radical cascade reactions involve functional groups migration, which leads structurally much more diverse, complex and valuable compounds not easily obtained through other methods. In this review, the recent achievements in unsaturated C–C bonds radical cascade reactions involving migration are summarized.

Recent advances in selective C–C bond coupling for ethanol upgrading over balanced Lewis acid-base catalysts

Ethanol is a considerable platform molecule in biomass conversion,which could be acquired in quantity through acetone-butanol-ethanol(ABE)fermentation.People have been working on the upgrading of ethanol to value added chemicals for decades.In the meantime,1-butanol and a series of value added products have been selectively generated through C–C bond coupling.In this mini-review,we focus on the recent advances in selective C–C bond formation over balanced Lewis acid-base catalysts such as modified metal oxide,mixed metal oxide,hydroxyapatite and zeolite confined transition metal oxide catalysts.Among them,Pd-MgAlO_x and Sr-based hydroxyapatite exhibit>70%1-butanol selectivity,while Zn——xZr_yO_z and Ta-Si BEA zeolite achieve>80%of isobutene and butadiene selectivity respectively.The mechanism and reaction pathway of C–C bond formation in each reaction system are described in detail.The correlation between C–C bond coupling and the acidity/basicity of the Lewis acid-base pairs from the surface of the catalysts are also discussed.

How long a C–C bond can be? An example of extraordinary long C–C single bond in 1,2-diarylamino-o-carborane

How long a C-C bond can be?A question has long fascinated chemists.This work reports an example of extraordinary long C-C bond distance of 1.990(4)?observed in single-crystal X-ray structure of 1,2-(NHMes)2-o-carborane(2;Mes=2,4,6-trimethylphenyl).DFT calculations show that hyperconjugation of lone pairs of the nitrogen atoms into the emptyσ^*orbital of the cage C-C bond is the origin of the bond elongation.Such hyperconjugation can be suppressed if the two nitrogen atoms in 2 are linked to a Lewis acidic germanium(Ⅱ)center.

The Novel Selective Reduction of the C-C Triple Bond

A novel reduction system is reported here in which the compounds with terminal C-C triple bond and disubstituted C-C triple bond react with NaBH4/Pd(PPh3)(4) in a base condition and only terminal C-C triple bond is reduced.

Copper-Catalyzed C-C(O)C Bond Cleavage of Monoalkylated β-Diketone: Synthesis of α,β-Unsaturated Ketones

A new and simple route for the synthesis of α,β-unsaturated ketones via cleavage of the C-C(O)C single bond of monoalkylated β-diketone has been described. The reaction was catalyzed by copper, a cheap transition metal in a weakly basic medium (K3PO4) at room temperature. To carry out this study, we first had to synthesize the monoalkylated β-diketones 1. Afterwards, α,β-unsaturated ketones 2 were obtained with high yields around 80%. Finally, all the products were characterized by 1H NMR, 13C NMR, and HRMS spectra. .

Further Report on A Novel Scission of Alkyl Carbonyl C-C Bond by Substituted 4-Hydroxyacetophenones

3-Methoxy-, 3, 5-dimethoxy-, and 3-phenyl-4-hydroxyacetophenones suffered alkyl carbonyl C-C bond scission to yield 4-hydroxybenzoate esters and 4-isopropenylphenols under standard conditions of ethylene ketal formation; the latter underwent in situ dimerization, cyclization, and rearrangement to give substituted indanols. The isopropenylphenol derived from 3,5-ditertbutyl-4-hydroxyacetophenone did not dimerize but condensed with its precursor to yield a substituted diphenylpropanone. 3-nitro-, 3,5-dinitro-, and 3,5-dibromo-4-hydroxyacetophenones on the other hand reacted normally to give ethylene ketals in good yields.

天然产物的C-糖基化研究进展

自然界中的天然产物在其结构上存在各种修饰,C糖-基化为其中一种比较稀少的修饰方式。C-C糖苷键的形成由C-糖基转移酶负责催化。含C-糖基的化合物多数来自微生物,但高等植物也会有少量积累。综述了近些年来在天然产物C-糖基化方面的研究工作,并对其在药物开发方面的潜力进行了展望。