Preface to special column on catalytic conversion of CO_(2)

With the increasing awareness of sustainable chemistry and green chemistry,catalytic conversion of carbon dioxide(CO_(2))into high value‐added and bulk chemicals is a promising tech‐nology that can utilize CO_(2) as an ideal C1 source while simulta‐neously storing renewable energy.Despite being frustrated with its thermodynamic stability and kinetic inertness,CO_(2) has been tamed for triggering catalytic constructions of highly‐valued entities like important hydrocarbon fuels and fine chemicals,mainly aiding by two scenarios:CO_(2) reduction and CO_(2)‐involved organic synthesis.Accordingly,science,industry and govern‐ment agencies have been devoted to leverage these synthetic tools in targeting the catalytic conversion of CO_(2).Therefore,it motivates us to organize the special column of“Catalytic Con‐version of CO_(2)”.The column contains 14 papers,including 4 reviews,4 communications and 6 articles,which cover the frontiers and most of the research aspects of catalytic con‐version of CO_(2).

Preparation and Characterization of Low Density Poly(Imino Imino Ketone)Foam

Poly（Imino Ketone） （PIK） is a group of novel high performance polymer material with excellent thermal properties and dissolubility. Aiming at the requirements of inertial confined fusion （ICF） studies on low density polymer foams, we firstly synthesized poly（imino imino ketone） （PIIK） by palladium catalyzed C-N cross-coupling reaction, and successfully prepared the PIIK foam material with a density of 80-300 mg/cm3 by using PIIK as the raw material with thermal-induced phase separation and lyophilization technique. Mercury injection method was used to determine the structure of PIIK foams, and the results indicated that the mean pore diameter was lower than 5 ~tm and it had relatively high voidage and specific surface area.

Visible-light photoredox-catalyzed carboxylation of aryl epoxides with CO_(2)

Herein, we report the first visible-light photoredox-catalyzed carboxylation of aryl epoxides with CO_(2)to synthesize hydroxy acid derivatives. A variety of valuable β-, γ-, δ-, ε–hydroxy acid derivatives are obtained in moderate to high yields under mild conditions. This protocol shows noteworthy functionalgroup compatibility, high chemo-and regioselectivities under transition-metal-free conditions with an inexpensive organo-dye as photosensitizer. Mechanistic studies indicate that the benzylic carbanion is generated as an intermediate via the sequential single electron transfer(SSET) process.

Photocatalytic dicarboxylation of strained C-C bonds with CO_(2) via consecutive visible-light-induced electron transfer

Dicarboxylic acids have a wide range of applications in the polymer industry to construct valuable materials.Photocatalysis has recently emerged as an efficient and sustainable strategy to generate dicarboxylic acids.However,photocatalytic dicarboxylation with CO_(2) is mainly limited to unsaturated bonds,and the dicarboxylation of C-C single bonds still remains a challenge.Herein,we report a photocatalytic dicarboxylation of C-C single bonds in strained rings with CO_(2) units via consecutive photo-induced electron transfer(ConPET).It is also the first photocatalytic reductive ring-opening reaction of cyclobutanes.Notably,this transition-metal-free protocol exhibits good functional group tolerance,broad substrate scope,facile scalability,and easy product derivatizations.Moreover,diacids can easily be derivatized to mainchain liquid crystalline polyesters.

Laser spectroscopy imaging technique coupled withnanomaterials for cancer diagnosis: A review

Laser spectroscopic imaging techniques have received tremendous attention in the-eld of cancer diagnosis due to their high sensitivity,high temporal resolution,and short acquisition time.However,the limited tissue penetration of the laser is still a challenge for the in vivo diagnosis of deep-seated lesions.Nanomaterials have been universally integrated with spectroscopic imaging techniques for deeper cancer diagnosis in vivo.The components,morphology,and sizes of nanomaterials are delicately designed,which could realize cancer diagnosis in vivo or in situ.Considering the enhanced signal emitting from the nanomaterials,we emphasized their combination with spectroscopic imaging techniques for cancer diagnosis,like the surface-enhanced Raman scattering(SERS),photoacoustic,fluorescence,and laser-induced breakdown spectroscopy(LIBS).Applications ofthe above spectroscopic techniques offer new prospectsfor cancer diagnosis.

Construction of Angularly Fused Tricyclic Compounds via Photo-induced Radical Cascade Cyclization

Photo-induced electron transfer (PET) of silyl enol ethers has been employed to synthesize several fused ring systems. However, the method has limited applicability due to its narrow substrate scope, low product yields, unsatisfactory stereo- and regioselectivity. Herein, we report a PET-triggered cascade reaction of silyl enolates that leads to the formation of angularly fused tricyclic scaffolds. The reaction exhibits broad substrate scope and excellent stereoselectivity. The regio- and stereoselectivity of this cascade reaction is elucidated via DFT calculation and conformational analysis.

Visible-light-driven thio-carboxylation of alkynes with CO_(2):facile synthesis of thiochromones

Difunctionalizing carboxylation of alkynes with CO_(2)is a sustainable and important strategy to generate valuable acrylate derivatives from both readily available starting materials.Such protocols,however,always suffer from the use of excess metallic reagents and transition metal residue.Herein,we report the first thio-carboxylation of alkynes with thiophenols and CO_(2),which is a visible-light-driven and transition metal-free process.In contrast to previous carboxylations of alkynes via two-electron activation of CO_(2),mechanistic and computational investigations suggest that the single-electron activation of CO_(2)is involved in the thio-carboxylation,rendering uniqueβ-carboxylation.The following cyclizing acylation affords important thiochromones efficiently.Moreover,the one-pot method features mild reaction conditions(room temperature,1 atmosphere of CO_(2)),high chemo-and regio-selectivity,easy scalability and facile derivatization of products to bioactive compounds.

Effect of loading content of copper oxides on performance of Mn-Cu mixed oxide catalysts for catalytic combustion of benzene

A series of Mn-Cu mixed oxide catalysts were prepared by precipitation method. The catalysts were characterized by N2 adsorp- tion-desorption, H2-TPR and XPS. When the loading ratio of manganese oxides to copper oxides was 8：2 or 7：3, the catalysts possessed better catalytic activity, and benzene was converted completely at 558 K. Results of H2-TPR showed that the loading of a small amount of copper oxides decreased the reduction temperature of catalysts. Results of XPS showed that the loading of a small amount of copper oxides increased the proportion of manganese and defective oxygen on the surface of catalysts, and stabilized manganese at higher oxidation state. And the catalyst with the loading ratio 7：3 was a little worse than 8：2, since the interaction between manganese oxides and copper oxides is too strong, copper oxides migrate to the surface of catalysts and manganese oxides in excess are immerged.

Visible-light-mediated external-reductant-free reductive cross coupling of benzylammonium salts with(hetero)aryl nitriles

Herein we report a novel visible-light-mediated external reductant-free reductive cross coupling for the construction of C sp2–C sp3 bonds.A variety of benzylammonium salts underwent selective coupling with(hetero)aryl nitriles to deliver important diarylmethanes under mild reaction conditions.Importantly,photocatalysts can be omitted for many cases,which might involve the electron donor acceptor(EDA)complex.Mechanistic studies indicated benzylic radicals might be involved as the key intermediates.Moreover,the in situ generated NMe3 via cleavage of C–N bond in ammonium salts acts as the electron donor,thus avoiding the use of external-reductant.

Computational Analysis of Synthetic Planning:Past and Future

Computer-aided synthesis planning(CASP)integrates intuition of chemists and reliability of computers.As an in-between of unique creativities of human beings and unparalleled calculational capability of computers,CASP has become an important tool used in academic and industrial research.With explosion of novel chemical reactions,increasing of computer performance,and revolution of algorithms,CASP will play more significant roles in the synthetic chemistry field,inspiring novel and highly efficient syntheses of natural products and drug candidates.In this article,we review the progress in computational analysis of synthetic planning from rule-based programs(e.g.,LHASA and SECS)in the early stage to machine learning(e.g.,neural networks and seq2seq methods)in more recent years.

Prediction of Multicomponent Reaction Yields Using Machine Learning

Prediction of reaction yields using machine learning(ML)can help chemists select high-yielding reactions and provide prior experience before wet-lab experimenting to improve efficiency.However,the exploration of a multicomponent organic reaction features many complex variables and limited number of experimental data,which are challenging for the application of ML.Herein,we perform yield prediction for the synthesis of 2-oxazolidones via Cu-catalyzed radical-type oxy-alkylation of allylamines and herteroaryl-methylamines with CO_(2),which is a three-component reaction.Using physicochemical descriptors as features to launch ML modelling,we find that XGBoost shows significantly improved performance over linear models and these features are effective for the yield prediction.Moreover,out-of-sample prediction indicates the application potential of the model.This study demonstrates great potential of regression-modelling-based ML in organic synthesis even with complex factors and a general small size of reaction data,which are generated from the classical research pattern of method for the inquiry of multicomponent reactions.

Cu-Catalyzed Selective Oxy-Cyanoalkylation of Allylamines with Cycloketone Oxime Esters and CO2

Summaryof main observation and conclusion The radical-initiated carboxylativecyclization of allylamines with CO2represents an efficientand highly promising strategy to afford valuable 2-oxazolidinones.However,the radical precursorsand pathways to generate radicals in such processes are still lim-ited.Herein,we report the firstCu-catalyzed selective oxy-cyanoalkylation of allylamines with cycloketone oxime esters and CO2viaC-C bond cleavage.Many cyanoalkyl-substituted 2-oxazolidinones are obtained in moderate togood yields withhigh regio-and chemo-selectivities.The utility ofthis re-dox-neutral and cyanide-free method is demonstrated with mild conditions,broad substrate scope,good functional group tolerance and easy scalability.

Chiral Pool Guided Syntheses of Polycyclic Natural Products

Chiral pools have been commonly utilized as inexpensive and versatile building blocks in organic synthesis.In this account,we provide an overview of our recent synthetic efforts toward polycyclic natural products using chiral natural small molecules(chiral pool)as starting materials.Key achievements during our syntheses include intermolecular Diels-Alder/intramolecular hetero-Diels-Alder cascade to enable modification of previously proposed biosynthetic pathway of bolivianine,Diels-Alder-type dimerization through a conjugated furanyl diene intermediate to achieve three types of lindenane[4+2]dimers,Iron-catalyzed reductive aldol reaction to construct core of rumphellclovane E and[3,3]-rearrangement along with vinylo-gous Pummerer rearrangement to make epoxyquinol substructure of JBIR-23/-24.In the final,the outlook is also presented.

Visible-Light-Driven Anti-Markovnikov Hydrocarboxylation of Acrylates and Styrenes with CO_(2)

Light-driven carbon dioxide(CO_(2))capture and utilization is one of the most fundamental reactions in Nature.Herein,we report the first visible-light-driven photocatalyst-free hydrocarboxylation of alkenes with CO_(2).Diverse acrylates and styrenes,including challenging tri-and tetrasubstituted ones,undergo anti-Markovnikov hydrocarboxylation with high selectivities to generate valuable succinic acid derivatives and 3-arylpropionic acids.In addition to the use of stoichiometric aryl thiols,the thiol catalysis is also developed,representing the first visible-lightdriven organocatalytic hydrocarboxylation of alkenes with CO_(2).The UV-vis measurements,NMR analyses,and computational investigations support the formation of a novel charge-transfer complex(CTC)between thiolate and acrylate/styrene.Further mechanistic studies and density functional theory(DFT)calculations indicate that both alkene and CO_(2)radical anions might be generated,illustrating the unusual selectivities and providing a novel strategy for CO_(2)utilization.

Thiocarbonylation of C(sp^(3))-H bonds in pyridylamines with CS;: Facile synthesis of pyrido[1,2-a]pyrimidine-4-thiones

Herein, a facile synthesis of valuable pyrido[1,2-a]pyrimidine-4-thiones is reported via novel thiocarbonylation of C(sp^(3))-H bonds with carbon disulfide(CS_(2)). This reaction features easy availability of substrates,good functional group tolerance, high yields, facile scalability and atom economy. Mechanistic investigations indicate that sulfate anion and sulfuric anhydride anion might be involved in this reaction.

Visible-light-driven external-photocatalyst-free alkylative carboxylation of alkenes with CO_(2)

Herein,we report a novel protocol for visible-light-driven alkylative carboxylation of alkenes with CO_(2) in the absence of external photocatalyst.Under the irradiation of visible light,a variety of 4-alkyl-1,4-dihydropyridines(alkyl-DHPs)serve as not only alkyl radical precursors but also photoexcited reductants probably with the potential to reduce benzyl radicals.Several styrenes and acrylates are applicable in this reaction to give structurally diverse carboxylic acids in good to excellent yields.These reactions feature mild reaction conditions(1 atm of CO_(2),room temperature,visible light,photocatalyst-and transition metalfree),good functional group tolerance,easy scalability,as well as high regio-,and chemo-selectivity.Mechanistic investigations provide evidence that alkyl radical,benzyl radical and carbanion might be involved in this reaction,providing a novel strategy for CO_(2) utilization.

Photochemical graft of γ-cyclodextrin's interior leading to in-situ charge-transfer complexes with unusual regioselectivity and its application in 3D photo-printing

Photoirradiation of anthraquinone(AQ)derivatives withγ-cyclodextrin(γ-CD)in aqueous solution led to aγ-CD derivative with a 9,10-dihydroxylanthracene grafting unprecedentedly at the 5′-position of one glucoside ofγ-CD in high efficiency.Meanwhile,another AQ enters into the remaining space of the 9,10-dihydroxylanthracene-occupiedγ-CD cavity to in-situ form a selfincluded quinhydrone charge transfer(CT)complex.The structure of the supramolecular CT complex was unambiguously demonstrated by 1 D and 2 D NMR(^(1)H NMR,^(13)C NMR,DEPT,^(1)H-^(1)H COSY,HSQC,HMBC,TOCSY,and ROESY)spectroscopies,which revealed a highly stereoselective stacking of the quinhydrone pairs in theγ-CD cavity.The supramolecular CT complex showed an unusually high binding affinity and improved oxidation resistance.Polyacrylamides bearingγ-CD or anthraquinone were respectively synthesized by co-polymerization of acrylamide with the corresponding monomer.Photoirradiation of aqueous mixtures containing these two types of polymers led to gelation,which was applied to 3 D photo-printing of soft materials.

High current CO_(2)reduction realized by edge/defect-rich bismuth nanosheets

CO_(2)electroreduction has been regarded as an appealing strategy for renewable energy storage.Recently,bismuth(Bi)electrocatalysts have attracted much attention due to their excellent formate selectivity.However,many reported Bi electrocatalysts suffer from low current densities,which are insufficient for industrial applications.To reach the goal of high current CO_(2)reduction to formate,we fabricate Bi nanosheets(NS)with high activity through edge/terrace control and defect engineering strategy.Bi NS with preferential exposure sites are obtained by topotactic transformation,and the processes are clearly monitored by in-situ Raman and ex-situ X-ray diffraction(XRD).Bi NS-1 with a high fraction of edge sites and defect sites exhibits excellent performance,and the current density is up to ca.870 mA·cm^(−2)in the flow cell,far above the industrially applicable level(100 mA·cm^(−2)),with a formate Faradaic efficiency greater than 90%.In-situ Fourier transform infrared(FT-IR)spectra detect*OCHO,and theoretical calculations reveal that the formation energy of*OCHO on edges is lower than that on terraces,while the defects on edges further reduce the free energy changes(ΔG).The differential charge density spatial distributions reveal that the presence of defects on edges causes charge enrichment around the C–H bond,benefiting the stabilization of the*OCHO intermediate,thus remarkably lowering theΔG.

A new sensitization strategy for achieving organic RTP in aqueous solution:tunable RTP and UC emission in supramolecular TTA-UC systems

Achieving room temperature phosphorescence(RTP)of heavy-atom-free organic molecules with near-infrared(NIR)emission in solutions is fascinating for medical and biological applications but is highly challengable.Herein,we report a new sensitization strategy to achieve RTP of heavy-atom-free fluorophores which served as energy acceptors in triplet-triplet annihilation upconversion(TTA-UC)by carefully designing the accommodated microenvironments through non-covalent interactions with a PAMAM dendrimer matrix.Sensitized RTP of a serial of diphenyl anthracene(DPA)derivatives peaked at 766 nm were observed for the first time in an aqueous solution with a maximal quantum yield of 1.4%.A ternary supramolecular assembling between the UC components and the dendrimers was formed via electrostatic interaction between the–COOH and peripheral amino groups.On one hand,it assured the efficient population of the triplet states of the fluorophore via triplet-triplet energy transfer(TTET)process;on the other hand,it restricted the motions of the fluorophores,and thus inhibited the nonradiative inactivation of the populated triplet states.These two aspects jointly contributed to the sensitized RTP of DPA units.Significantly,the microenvironment in which the annihilators resided could be regulated by adjusting the ratio of carboxyl to amino groups(–COOH/–NH_(2)),when–COOH/–NH_(2)<1,the annihilators were mainly immobilized at the periphery of the dendrimers,leading to the sensitized RTP,and when COOH/–NH_(2)>1,the UC components could be partly driven to the hydrophobic cavities of the dendrimers,resulting an unprecedentedly simultaneous emission of upconverted fluorescence and down-converted phosphorescence of the annihilators.

氮烷基化反应的新突破:从亲核取代氮烷基化到自由基对映性收敛氮烷基化

Enantiopure aliphatic amines are common chiral synthons and catalysts for the asymmetric synthesis of natural products,pharmaceutical agents,agrochemicals,and functional materials[1].Therefore,the development of general,straightforward,and practical methodologies to access enantioenriched aliphatic amines under mild reaction conditions is a long-pursued goal in organic chemistry[2,3].Among them,the N-alkylation of amines with alkyl halides(S_(N)1 and S_(N)2),which was discovered by Hofmann in 1850,is the most straightforward and widely applied approach to construct C(sp^(3))AN bonds due to the readily available starting materials[4](Scheme 1a).Although investigated for more than 150 years,its asymmetric version has been early areas of endeavor with the only modest success,which largely relied on the use of enantioenriched alkyl halides.