Metal-Free Multicomponent Tandem Polymerizations of Alkynes, Amines, and Formaldehyde toward Structure- and Sequence-Controlled Luminescent Polyheterocycles

The Introduction of the Radical Cascade Reaction into Polymer Chemistry: A One-Step Strategy for Synchronized Polymerization and Modification

Polymerization and modification play central roles in polymer chemistry and are generally implemented in two steps, which suffer from the time-consuming two-step strategy and present considerable challenge for complete modification. By introducing the radical cascade reaction (RCR) into polymer chemistry, a one-step strategy is demonstrated to achieve synchronized polymerization and complete modification in situ. Attributed to the cascade feature of iron-catalyzed three-component alkene carboazidation RCR exhibiting carbon-carbon bond formation and carbon-azide bond formation with extremely high efficiency and selectivity in one step, radical cascade polymerization therefore enables the in situ synchronized polymerization through continuous carbon-carbon bond formation and complete modification through carbon-azide bond formation simultaneously. This results in a series of α, β, and γ poly(amino acid) precursors. This result not only expands the methodology library of polymerization, but also the possibility for polymer science to achieve functional polymers with tailored chemical functionality from in situ polymerization.

Vinyl Iodide Containing Polymers Directly Prepared via an Iodo-yne Polymerization

Postpolymerization modifications are a prominent route for tuning polymer properties and diversifying materials. Thus, polymers containing robust chemical handles are desirable. Vinyl iodide functionality is commonly enlisted for selective transformations on small molecules, but these chemistries, while efficient enough for postpolymerization modifications, are less frequently performed on macromolecules due to limited methods to install vinyl iodide groups into polymers. Here, we present an iodo-yne polymerization involving diynes and diiodoperfluoroalkanes to facilely give semifluorinated polymers with vinyl iodide groups throughout the polymer chain. The iodo-yne polymerization yields polymers of at least 6 kDa while open to air in aqueous solvent. We demonstrate that the iodo-yne polymers can be modified at the vinyl iodide functionality via a variety of metal-catalyzed cross-coupling reactions. Additionally, the iodide can be eliminated to give electronically activated alkynes that can undergo cycloaddition with azides. Taken together, this work will push the current boundaries of functional polymers and assist in the development of modernized, smart materials.

Synthesis of polymeric topological isomers based on sequential Ugi-4CR and thiol–yne click reactions with sequence-controlled amino-functionalized polymers

Polymeric topological isomers have been designed and synthesized with sequence-controlled amino functionalized polymers.

Metal-free polycycloaddition of aldehyde-activated internal diynes and diazides toward post-functionalizable poly(formyl-1,2,3-triazole)s

A metal-free polycycloaddition of aldehyde-activated internal diynes and diazides was successfully established and post-functionalizable poly(formyl-1,2,3-triazole)s were readily produced.

Multicomponent polymerization toward biodegradable polymers with diverse responsiveness in tumor microenvironments

Multicomponent polymerization (MCP), as a powerful synthetic tool, has been widely utilized to prepare diverse functional polymers for optical, electronic, and biomedical applications.

Direct Construction of Acid-Responsive Poly(indolone)s through Multicomponent Tandem Polymerizations

Multicomponent polymerizations (MCPs) as a burgeoning field in polymer chemistry has proved to be a powerful and popular tool for the synthesis of functional polymer materials with diverse and complex structures. To explore the general applicability of MCPs and enrich the product structures of MCPs, multicomponent tandem polymerizations (MCTPs) with great synthetic simplicity and efficiency were pursued. In this work, MCTPs of N-(2-iodophenyl)-3-phenyl-N-tosylpropiolamide, aromatic terminal alkynes, and diamines were explored through combining Sonogashira coupling and Michael addition reaction in a one-pot procedure. The MCTPs could proceed efficiently and conveniently under mild conditions with Pd(PPh₃)₂Cl₂, CuI, and i-Pr₂NEt, affording 12 poly(indolone)s with unique structures and high M_ws (up to 30400 g/mol) in high yields (up to 97%). The poly(indolone)s possess a unique acid-triggered fluorescence "turn-on" response which could realize specific detection of CF₃SO₃H from other inorganic and organic acids through a rapid acid-catalyzed reaction from enamine to ketone.

Multicomponent Polymerizations of Alkynes, Sulfonyl Azides, and 2-Hydroxybenzonitrile/2-Aminobenzonitrile toward Multifunctional Iminocoumarin/Quinoline-Containing Poly(N-sulfonylimine)s

Multicomponent polymerizations (MCPs) provide a powerful synthetic tool for the construction of polymers with complex structures and multifunctionalities, owing to their great structural diversity, mild condition, high efficiency, simple procedure, and environmental benefit. They possess significant advantages in synthesizing heteroatom-rich or heterocycle-containing functional polymers through directly constructing fused heterocycles from the MCP. In this work, the MCPs of diynes, disulfonyl azides, and 2-hydroxybenzonitrile or 2-aminobenzonitrile were reported under the catalysis of CuCl and Et₃N, generating iminocoumarin/quinoline-containing poly(N-sulfonylimine)s with high molecular weights (up to 37700 g/mol) and high yields (up to 96%). The MCPs enjoy a wide monomer scope and high atom economy, releasing N₂ as the only byproduct. The fluorescent poly(N-sulfonylimine) can be utilized for sensitive and selective detection of Ru³⁺, which also possesses antibacterial properties. The efficient MCPs could produce polymers with unique structures and functionalities, thereby accelerating the development of polymer materials.

Catalyst-Free Click Polymerization of CO2 and Lewis Monomers for Recyclable C1 Fixation and Release

Conversion of carbon dioxide (CO₂) into valuable chemicals in gentle conditions is a great challenge in sustainable and energy chemistry. Here we report a CO₂-participated polymerization using frustrated Lewis pair (FLP) as the monomer, which allows us to obtain well-defined CO₂/FLP alternating copolymers with high molecular weights (∼50000) and quantitative conversions (∼95%), resembling a "click" polymerization of CO₂ gas and FLP molecules. In comparison to other CO₂-based polymerizations, this method features spontaneity, catalyst-free, and speediness, as well as can realize in ambient temperature (20 °C) and low CO₂ pressure conditions (1.0 atm). Moreover, owing to the dynamic covalent bonding between CO₂ and FLP unit, such a class of alternating copolymers upon heating can depolymerize into initial monomers and release CO₂, which could make them as recyclable smart materials for reversible C1 fixation and release.

Highly fluorescent organic polymers for quenchometric determination of hydrogen peroxide and enzymatic determination of glucose

Strongly fluorescent polymers (FPs) were prepared from citric acid and ethylenediamine via a hydrothermal approach. The FPs display low toxicity, water solubility, a quantum yield of 91%, good photostability and stability in the physiological pH range. Ferric ions are found to quench the fluorescence which is best measured at excitation/emission wavelengths of 350/440 nm. Because ferric ions (Fe³⁺) can quench the fluorescence of FPs, a fluorometric method was developed for fast detection of Fe³⁺ and within 1 min. FPs can also be used indirectly for the detection of hydrogen peroxide because of its fast Fenton reaction with Fe²⁺ to generate of Fe³⁺. The detection limits are 8 μM for Fe(III) and 0.6 μM for H₂O₂. On the basis of the glucose oxidase catalyzed of glucose and the Fenton reaction, the FPs can also be used to quantify glucose with a linear response in the 0.5-10 μM concentration range. Graphical abstract A new type of polymer with high fluorescence quantum yield was prepared. It is shown to enable the fast detection of ferric ions, hydrogen peroxide and glucose based on quenching and on the glucose oxidase and Fenton reactions.

Functional Poly(dihalopentadiene)s: Stereoselective Synthesis, Aggregation-Enhanced Emission and Sensitive Detection of Explosives

The development of polymeric materials with novel structures and unique properties and functionalities is of both academic and industrial significance. In this work, functional poly(dihalopentadiene)s were synthesized by boron trihalide-mediated multicomponent polymerization routes in a stereoselective manner. The polymerizations of tetraphenylethylene-containing diyne, BX₃ (X = Cl, Br) and p-tolualdehyde proceed smoothly in dichloromethane under mild conditions to afford high molecular weight poly(dihalopentadiene)s with a predominant (Z,Z)-configuration in moderate to good yields. The reaction conditions and the boron trihalide used were found to have great effects on the stereochemistry of the resulting polymer structures. The obtained poly(1,5-dihalo-(Z,Z)-1,4-pentadiene)s possess high thermal stability and good film-forming ability. Their thin films show high refractive index of 1.9007⁻1.6462 in a wide wavelength region of 380⁻890 nm with low optical dispersion. The polymers are weakly emissive in dilute solutions but become highly emissive upon aggregated, demonstrating a unique phenomenon of aggregation-enhanced emission. Their nanoaggregates in aqueous media can serve as sensitive fluorescent chemosensors for the detection of explosives with a superamplification effect and a low detection limit.

Room Temperature One-Step Conversion from Elemental Sulfur to Functional Polythioureas through Catalyst-Free Multicomponent Polymerizations

The utilization of sulfur is a global concern, considering the abundant and cheap source of sulfur from nature and petroleum industry, its limited consumption, and the safety/environmental problems caused during storage. The economic and efficient transformation of sulfur remains to be a great challenge for both academia and industry. Herein, a room temperature conversion from sulfur to functional polythioureas was reported through a catalyst-free multicomponent polymerization of sulfur, aliphatic diamines, and diisocyanides in air with 100% atom economy. The polymerization enjoys quick reaction and wide monomer scope, which affords 16 polythioureas with well-defined structures, high molecular weights ( M_ws up to 242 500 g/mol), and excellent yields (up to 95%). The polythioureas can be utilized to detect mercury pollution with high sensitivity ( K_sv = 224 900 L/mol) and high selectivity, clean Hg²⁺ with high removal efficiency (>99.99%) to achieve drinking water standard, and monitor the real-time removal process by fluorescence.

Sequence-definition from controlled polymerization: the next generation of materials

An overview is given on the state-of-the-art in synthesis of sequence-controlled and sequence-defined oligomers and polymers.

Room temperature multicomponent polymerizations of alkynes, sulfonyl azides, and N-protected isatins toward oxindole-containing poly(N-acylsulfonamide)s

The development of a new polymerization methodology affords polymer materials with new structures and functionalities.

Periodic polymers based on a self-accelerating click reaction

Self-accelerating click chemistry was used to prepare sequence-controlled periodic polymers with ultrahigh molecular weights or a cyclic molecular topology.

Catalyst-free synthesis of tetrahydropyrimidines via formal [3+3]-cycloaddition of imines with 1,3,5-hexahydro-1,3,5-triazines

A practical and environmentally benign synthesis of poly-substituted tetrahydropyrimidines from readily available starting materials has been developed. This process features an unprecedented intermolecular formal [3+3]-annulation of imines and 1,3,5-hexahydro-1,3,5-triazines under catalyst-free conditions. Importantly, differing from previous transformations, the 1,3,5-triazines are firstly utilized as formal 1,3-dipoles in cycloaddition reactions.

A practical and environmentally benign synthesis of poly-substituted tetrahydropyrimidines via formal [3+3]-annulation of imines and 1,3,5-hexahydro-1,3,5-triazines under catalyst-free conditions has been developed.

Multicomponent spiropolymerization of diisocyanides, alkynes and carbon dioxide for constructing 1,6-dioxospiro[4,4]nonane-3,8-diene as structural units under one-pot catalyst-free conditions

A novel multicomponent spiropolymerization was developed by using diisocyanide, alkyne and CO₂, and 1,6-dioxospiro[4,4]nonane-3,8-diene was instantly formed.

A one-pot multicomponent approach to a new series of morphine derivatives and their biological evaluation

Morphine derivatives displaying a mixed MOR/DOR biological characteristic were synthesized through a one-pot multicomponent approach.

Selective synthesis of tetrahydroimidazo[1,2-a]pyridine and pyrrolidine derivatives via a one-pot two-step reaction

In the presence of triethylamine, the addition reaction of substituted α-amino acid alkyl esters with dialkyl but-2-ynedioate afforded active β-enamino esters, which in turn reacted with aromatic aldehydes and malononitrile to give tetrahydroimidazo[1,2-a]pyridine derivatives in moderate yields.