When nanocarbon science meets with molecular machine:A new type of mechanically interlocked molecules(MIMs)

The discovery of new carbon nanomaterials such as fullerenes,carbon nanotubes,graphene,and graphyne has always driven the development of various fields of science[1].The arrangement of carbon atoms largely influences their properties.In the past decade,the atomic-precision synthesis and study of molecular nanocarbons,which is the sub-structures of larger carbon nanostructures,have attracted huge attention[2].Among them,the synthesis of cycloparaphenylene(CPP)(the substructure of carbon nanotubes)has been developed considerably since 2008[3].Recently,topologically complex nanocarbon[4]starting from CPP or oligoparaphenylene-derived carbon nanohoop has been explored as a new type of MIM,which undoubtedly revolutionizes a wide range of sciences,especially in the field of molecular machine(Fig.1)[5].

Organic Brønsted Acid-Catalyzed Stereoselective Cationic RAFT Polymerization:The Effect of RAFT Agents

The tacticity of vinyl polymers is a key factor affecting the properties of materials.Recently,organic Brønsted acids have been demonstrated as effective catalysts for the development of highly stereoselective cationic reversible addition-fragmentation chain transfer(RAFT)polymerizations of vinyl ethers,in which the use of RAFT agents could allow the control the molecular weight and tacticity of polymer products simultaneously.However,the effect of RAFT agents on the tacticity-regulation remains elusive and lacks of investigation.In this study,we synthesized four types of RAFT agents and evaluated their influence in the stereoselective cationic polymerization of isobutyl vinyl ether in the presence of PADI as a Brønsted acid catalyst,which unveils that the Z group of RAFT agents could not only affect the polydispersity of the products,but also exert a profound effect on the stereoselectivity.After extensive screening of the RAFT agents,high stereoregularity(isotacticity,90%m)was obtained when using dithiocarbonate ester-type RAFT agents with a benzyloxy Z group.

Chemical Synthesis of Carbon Nanorings and Nanobelts

CONSPECTUS:The discovery and creation of new forms of carbon have always transformed the scientific landscape.For example,the discoveries of fullerenes,carbon nanotubes(CNTs),and graphenes have opened doors to the science of nanometersized carbon allotropes,otherwise known as nanocarbons.Since then,researchers worldwide have unveiled their outstanding physical and chemical properties,and a number of applications and technologies have arisen in not only materials science but also biological research fields.The synthesis and study of this privileged class of“single-molecule”compounds has become one of the most engaging subjects in chemistry and holds huge promise to establish new fields in molecular science.However,there have been huge gaps between established small-molecule chemistry and nanocarbon science.In the particular case of CNTs,it is still not possible to access structurally uniform CNTs.Although a wide range of synthetic methods have been reported,CNTs are generally accessed as a mixture of various structures.One logical strategy to achieve full synthetic control over CNTs is to build up from a template molecule with structural precision(the so-called“growth-from-template”strategy),where a short CNT segment molecule represents an initial synthetic target.To this end,organic synthesis techniques are our most powerful tools to synthesize short CNT segments such as carbon nanorings and carbon nanobelts.This Account highlights our 16-year campaign in the synthesis and application of carbon nanorings and carbon nanobelts.The first topic is the synthesis of carbon nanorings(cycloparaphenylenes)as substructures of CNTs.The second topic is the synthesis of armchair and zigzag carbon nanobelts,which consist solely of fully fused hexagonal rings and provide a continuous double-stranded cylindrical framework.The third topic is the synthesis of methylene-bridged cycloparaphenylene,an aromatic belt containing nonhexagonal rings,in which the cyclic paraphenylene chain is ladderized by methylene bridges.This nonalternant aromatic belt can be regarded as segments of nonconventional CNTs.During our extensive investigation,we found that the careful design of strainless macrocyclic precursors is crucial to the success of the synthesis of these curvedπ-conjugated nanorings and nanobelts.In the final section,some of the representative size-dependent properties of these nanorings/belts,including their HOMO−LUMO energies,strain energies,and photophysical properties,are summarized.In addition to basic properties,the utilization of these compounds as supramolecular hosts and organic materials is also briefly introduced.We hope this Account will inspire the development of new forms of nanocarbon molecules that would open doors to new fields and applications.

Merging cobalt catalysis and electrochemistry in organic synthesis

There is an increasing demand of using the low-cost and sustainable cobalt to replace its noble congeners(rhodium and iridium)as reflected by the recent upsurge of cobalt catalysis in the diverse organic transformations.Since all the redox reactivity of cobalt catalysis highly relies on the capability of the interconversion between their oxidation states(most frequently+1,+2 and+3),electrochemistry perfectly meets such a require ment owing to its outstanding perfo rmance in the redox manipulation.In this review,we highlight the recent advances in the merger of cobalt catalysis and electrochemistry in organic synthesis.

Electrochemistry enabled selective vicinal fluorosulfenylation and fluorosulfoxidation of alkenes

Both sulfur and fluorine play important roles in organic synthesis, the life science, and materials science.The direct incorporation of these elements into organic scaffolds with precise control of the oxidation states of sulfur moieties is of great significance. Herein, we report the highly selective electrochemical vicinal fluorosulfenylation and fluorosulfoxidation reactions of alkenes, which were enabled by the unique ability of electrochemistry to dial in the potentials on demand. Preliminary mechanistic investigations revealed that the fluorosulfenylation reaction proceeded through a radical-polar crossover mechanism involving a key episulfonium ion intermediate. Subsequent electrochemical oxidation of fluorosulfides to fluorosulfoxides were readily achieved under a higher applied potential with the adventitious H;O in the reaction mixture.

Photocatalytic divergent decarboxylative amination: a metal-free access to aliphatic amines and hydrazines

Nitrogen-containing motifs are widely present in natural products, bioactive molecules, and drugs. Accordingly, effective synthetic methods with high efficiency and diversity are highly desirable. Here, we present the invention of a facile, visible lightmediated decarboxylative C(sp^(3))–N bond-forming reaction by employing abundant carboxylic acids as the feedstock and a commercial diazirine as a nitrogen donor. This process is amenable to access both imines and diaziridines, as the corresponding masked amines and hydrazines, through a selectable single or double nitrogen transfer from the diazirine, respectively. This divergent approach works well in both directions with various alkyl carboxylic acids, including primary, secondary, and tertiary acids, as well as natural products and drugs, thus affording a rapid, metal-free approach to build nitrogen-containing molecule libraries with considerable structural diversity, which could thus benefit the related study in context of chemical biology and drug discovery.

Organocatalytic stereoselective cationic polymerization of vinyl ethers by employing a confined BrΦnsted acid as the catalyst

The properties of poly(vinyl ether)s(PVEs)are highly dependent on their tacticity,and the appealing thermoplastics features of isotactic PVEs have drawn considerable efforts to develop stereoselective cationic polymerization methods to access this class of polymers.However,reported methods that could achieve a high degree of tacticity control are limited to process employing metal-based Lewis acids,and with various limitations on catalyst loading,monomer scope,etc.Here,we introduce a metal-free stereoselective cationic polymerization of vinyl ethers by employing a class of chiral confined Br?nsted acids,imidodiphosphorimidates(IDPis),as the catalyst.This organocatalytic approach features its metal-free conditions,high efficiency,high stereoselectivity,single catalyst system,operation simplicity,etc.

Highly Site-selective Electrooxidation Providing Facile Entries to Functionalized Aromatic Acetals

Given the fact that aldehydes are among the most fundamental and versatile building blocks in organic syn thesis,the development of highly efficient and selective methods for their preparation,especially for those delicatelk functionalized ones remains sigmificant challenging.To address such an issue,Xu and co-workers have recently reported an elegant electrochemical approach realizing the highly regioselective oxidation of functionalized methyl aromatic hydrocarbons towards the desired aromatic acetals without the use of any chemical oxidants or transition metal catalysts These acetals can be then conveniently converted into corresponding structurally diverse aldehydes via hydrolysis.In addition,the synthetic practicability of current method was further highlighted as the key step in the preparation of the antihypertensive drug telmisartan.This work has been published in the Nature Communications and can be reached at https://doi.orp/10.1038/s41467-020-16519-8.

Cobalt-catalyzed modular assembly towardmulti-functionalized furan derivatives

A cobalt-catalyzed modular[3+2]assembling of unsaturated hydrocarbons andβ-dicarbonyls isreported.This protocol features mild reaction conditions and a broad substrate scope,providing facileentries toward diverse multi-functionalized dihydrofuran and furan derivatives.

基于电化学钴催化C-H活化的多样化手性骨架的构建

Transition metal-catalyzed C-H functionalizations,which transform ubiquitous C-H bonds into diverse and valuable functionalities in a single step,have emerged as a direct and efficient methodology for constructing synthetically useful and multifunctional organic molecules[1].Despite the significant advantages,some drawbacks such as the requirement of a stoichiometric amount of chemical oxidant and the resulting low functional group tolerance,byproduct generation and separation issues remain to be solved(Fig.1a).Notably,the development of electrochemistry has introduced new dimensions to the field of organic synthesis[2].Employing electric energy as both an oxidant and a reductant in a single process,electrochemistry offers numerous advantages,including mild reaction conditions,a wide substrate scope,and enhanced sustainability.