Sequence Regulated Poly(ester-amide)s Based on Passerini Reaction

Versatile Routes to Functional RAFT Chain Transfer Agents through the Passerini Multicomponent Reaction

The widespread adoption of RAFT polymerization stems partly from the ease and utility of installing a functional chain transfer agent onto the ends of the generated polymer chains. In parallel, the Passerini multicomponent reaction offers great versatility in converting a wide range of easily accessible building blocks to functional materials. In this work, we have combined the two approaches such that a single, commonly available, RAFT agent is used in Passerini reactions to generate a variety of multifunctional RAFT chain transfer agents containing ester linkages. Reactions to generate the multifunctional RAFT agents took place under mild conditions and in good yields. The resulting Passerini-RAFT agents were able to exert control over radical polymerization to generate materials of well-defined molecular weights and dispersity. Furthermore, the presence in these polymer cores of ester and amide functionality through the Passerini chemistries, provided regions in the materials which are inherently biodegradable, facilitating any subsequent biomedical applications. The work overall thus demonstrates a versatile and facile synthetic route to multi functional RAFT chain transfer agents and biodegradable polymers.

An Update on Isocyanide-Based Multicomponent Reactions in Polymer Science

Developments and progress in polymer science are often inspired by organic chemistry. In recent years, multicomponent reactions-especially the Passerini and Ugi reactions-have become very important tools for macromolecular design, mainly due to their modular character. In this review, the versatility of the Passerini and Ugi reactions in polymer science is highlighted by discussing recent examples of their use for monomer synthesis, as polymerization techniques, and for postpolymerization modification, as well as their suitability for architecture control, sequence control, and sequence definition.

Fluorescent Cell-Conjugation by a Multifunctional Polymer: A New Application of the Hantzsch Reaction

Multicomponent reactions (MCRs) can form unique structures with interesting functions, therefore, multifunctional polymers might be simply prepared using MCRs as coupling tools to simultaneously link and generate different functional groups. To verify this concept, a new fluorescent polymer containing phenylboronic acid has been facilely prepared via a one pot method by combining the Hantzsch reaction with reversible addition-fragmentation chain transfer (RAFT) polymerization. The Hantzsch-RAFT system has been found robust to smoothly achieve predesigned multifunctional polymer, which can be used for cell conjugation through the interaction between phenylboronic acid and glycoprotein on cell membrane. The conjugated cells could be directly observed due to the fluorescent Hantzsch moiety in the polymer chain, demonstrating a new application of the old Hantzsch reaction (>130 years) outside organic chemistry. Meanwhile, the conjugated cells remained excellent dispersity in the presence of coagulation protein (lectin), implying that multifunctional polymer a possible anticoagulant for cell separation. We believe that the current research paves a new way to exploit new applications of MCRs in interdisciplinary fields and might prompt the development of other multifunctional polymers based on different MCRs.

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

Sequence-controlled polymers, including biopolymers such as DNA, RNA, and proteins, have attracted much attention recently because of their sequence-dependent functionalities. The development of an efficient synthetic approach for non-natural sequence-controlled polymers is hence of great importance. Multicomponent polymerizations (MCPs) as a powerful and popular synthetic approach for functional polymers with great structural diversity have been demonstrated to be a promising tool for the synthesis of sequence-controlled polymers. In this work, we developed a facile metal-free one-pot multicomponent tandem polymerization (MCTP) of activated internal alkynes, aromatic diamines, and formaldehyde to successfully synthesize structural-regulated and sequence-controlled polyheterocycles with high molecular weights (up to 69 800 g/mol) in high yields (up to 99%). Through such MCTP, polymers with the in situ generated multisubstituted tetrahydropyrimidines or dihydropyrrolones in the backbone and inherent luminescence can be easily obtained with high atom economy and environmental benefit, which is inaccessible by other synthetic approaches.

Facile Synthesis of H2O2-Cleavable Poly(ester-amide)s by Passerini Multicomponent Polymerization

We report the straightforward synthesis of two types of H₂O₂-cleavable poly(ester-amide)s (P1 and P2) via the Passerini multicomponent polymerization (P-MCP) of 4-formylbenzeneboronic acid pinacol ester with 1,6-diisocyanohexane and 1,6-hexanedioic acid or a polyethylene glycol (PEG) dicarboxylic acid. The H₂O₂-cleavable phenylboronic acid ester was integrated into the polymer backbone by the in situ formed benzyl ester bond. GPC and ¹H NMR confirmed the complete H₂O₂-triggered degradation of these polymers in aqueous medium by a mechanism of sequential oxidation of phenylboronic acid ester and self-immolative elimination. Compared with the hydrophobic polymer P1, the PEG-based water-soluble polymer P2 degraded much faster even at a lower H₂O₂ concentration. Cytocompatible nanoparticles of polymer P1 loaded with fluorescent Nile red were fabricated, and controlled release of Nile red in response to H₂O₂ was achieved, thus, demonstrating the utility of these polymers as potential H₂O₂-responsive delivery vehicles.

The Hantzsch reaction in polymer chemistry: synthesis and tentative application

The recent utilization of the tetra-component Hantzsch reaction in polymer chemistry has been summarized.

Synthesis and unimolecular micellar behavior of amphiphilic star-shaped block copolymers obtained via the Passerini three component reaction

A series of new amphiphilic star-shaped block copolymers with hydrophobic cores and hydrophilic shells was synthesized, using the Passerini three component step-growth polymerization (Passerini-3CP).

Addressing the mid-point of polymer chains for multiple functionalization purposes through sequential thiol–epoxy ‘click’ and esterification reactions

A synthetic strategy is devised for the preparation of mid-chain multifunctional polymers.

Single-chain nanoparticles containing sequence-defined segments: using primary structure control to promote secondary and tertiary structures in synthetic protein mimics

We investigated intra-chain multicomponent reactions to synthesize single-chain nanoparticles (SCNP) containing sequence-defined segments at each cross-link, creating materials featuring multiple protein-inspired elements.

Regulating sequence distribution of polyethers via ab initio kinetics control in anionic copolymerization

Design principles for regulating the sequence distribution of polyethers in anionic copolymerization have been provided through kinetics studies and numerical calculation.

Sequence regulation in the living anionic copolymerization of styrene and 1-(4-dimethylaminophenyl)-1-phenylethylene by modification with different additives

Sequence regulation in the copolymerization of styrene and 1-(4-dimethylaminophenyl)-1-phenylethylene is conveniently achievedviathe modification of additives.

High-throughput polymer screening in microreactors: boosting the Passerini three component reaction

The Passerini three-component reaction (Passerini-3CR) has been studied via on-line microreactor/electrospray ionisation mass spectrometry (MRT/ESI-MS) reaction monitoring to demonstrate the high-throughput screening potential of microreactors for macromolecular design.

Effect of Molecular Structure on Stability of Organic Nanoparticles Formed by Bodipy Dimers

The objective was to evaluate the stability of organic nanoparticles made from Bodipy dimers. Bodipy dimers with different length of linkers were synthesized via multicomponent Passerini reaction, and could form the fluorescent nanoparticles (FNPs) through nanoprecipitation. Bodipy-dimers FNPs with long chain linker indicated better stability in biological condition than those with short one as revealed by changes of diameter and size distribution. The FNPs possessed high physical homogeneity and low cytotoxicity. The molecular structure dependent stability was also validated by confocal laser scanning microscope based on the dissociation-induced fluorescence recovering. Importantly, stable FNPs also could be used to load hydrophobic cargoes and deliver them into cytoplasm. We believe this systematic study between structure and stability might open new opportunities for designing stable nanoparticles for various applications.

Metal-Free, Multicomponent Synthesis of Pyrrole-Based π-Conjugated Polymers from Imines, Acid Chlorides, and Alkynes

Multicomponent coupling reactions (MCRs) are becoming increasingly used in the synthesis of macromolecules, as they can allow the rapid generation of libraries of materials as a method to tune properties. MCRs could prove particularly useful in the synthesis of π-conjugated polymers in which structural changes are necessary for fine-tuning of electronic properties. We describe here the first metal-free multicomponent approach to conjugated polymers. This reaction exploits the coupling of imines, acid chlorides, and (catechyl)PPh to generate phospha-münchnone-containing polymers, which can be converted to poly(pyrroles) via cycloaddition. The platform allows for the efficient synthesis of families of high molecular weight polymers in one step from readily available monomers.

Controlling molecular weight and polymer architecture during the Passerini three component step-growth polymerization

A new approach to control the molecular weight and polymer architecture using the Passerini three-component step-growth polymerization is described.

Synthesis of polypyrrole–polystyrene composite microspheres via pseudo-multicomponent heterophase polymerization and the potential application on Cr(vi) removal

Polypyrrole–polystyrene (PPy–PS) composite hollow microspheres with a dry-plum-like morphology were prepared via pseudo-multicomponent heterophase polymerization in an aqueous dispersion system.

One-pot sequential multicomponent reaction and a multicomponent polymerization method for the synthesis of topologically different polymers

The synthesis of topologically different polymers via a one-pot sequential multicomponent reaction and multicomponent polymerization is reported.

Multicomponent Copolycondensates via the Simultaneous Hantzsch and Biginelli Reactions

The tricomponent Biginelli reaction and the tetracomponent Hantzsch reaction which share the same reaction modules (aldehyde and β-ketone ester) have been found compatible. Therefore, a series of copolycondensates containing both 1,4-dihydropyridine (1,4-DHP) and 3,4-dihydropyrimidin-2(1H)-one (3,4-DHPM) in the main chains via the simultaneous Hantzsch and Biginelli reactions have been facilely synthesized. The ratio of 1,4-DHP and 3,4-DHPM in the polymer congeners could be easily tuned by changing the feeding ratio of reactants, and the thermal properties of the obtained polymers are thereby adjusted. As the first attempt to prepare copolycondensate through the combination of two multicomponent reactions (MCRs), the current method revealed and utilized the interesting compatibility between MCRs, providing a new strategy to prepare multicomponent functional polymers.

Endosomal-Escape Polymers Based on Multicomponent Reaction-Synthesized Monomers Integrating Alkyl and Imidazolyl Moieties for Efficient Gene Delivery

As one of the toughest tasks in the course of intracellular therapeutics delivery, endosomal escape must be effectively achieved, particularly for intracellular gene transport. In this report, novel endosomal-escape polymers were designed and synthesized from monomers by integrating alkyl and imidazolyl via Passerini reaction and reversible addition-fragmentation chain transfer polymerization (RAFT). After introducing the endosomal-escape polymers with proper degrees of polymerization (DPs) into poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) as the gene delivery vectors, the block copolymers exhibited significantly enhanced hemolytic activity at endosomal pH, and the plasmid DNA (pDNA)-loaded polyplexes showed efficient endosomal escape compared with PDMAEMA, ultimately achieving dramatically increased gene transfection efficacy. These results suggest that the polymers that integrate alkyl and imidazolyl moieties for efficient endosomal escape have wide potential applications for intracellular gene delivery.

Design and synthesis of novel PEG-conjugated 20(S)-camptothecin sulfonylamidine derivatives with potent in vitro antitumor activity via Cu-catalyzed three-component reaction

In our continuing search for camptothecin (CPT)-derived antitumor drugs, novel structurally diverse PEG-based 20(S)-CPT sulfonylamidine derivatives were designed, synthesized via a Cu-multicomponent reaction (MCR), and evaluated for cytotoxicity against four human tumor cell lines (A-549, MDA-MB-231, KB, and KBvin). All of the derivatives showed promising in vitro cytotoxic activity against the tested tumor cell lines, and were more potent than irinotecan. Significantly, these derivatives exhibited comparable cytotoxicity against KBvin, while irinotecan was less active against this cell line. With a concise efficient synthesis and potent cytotoxic profiles, especially significant activity towards KBvin, these compounds merit further development as a new generation of CPT-derived PEG-conjugated drug candidates.

Synthesis of Sequence-Regulated Polymers: Alternating Polyacetylene through Regioselective Anionic Polymerization of Butadiene Derivatives

We hereby report a strategy to synthesize sequence-regulated substituted polyacetylenes using living anionic polymerization of designed monomers, that is, 2,4-disubstituted butadienes. It is found that proper substituents, such as 2-isopropyl-4-phenyl, lead to nearly 100% 1,4-addition during the polymerization, thus, giving product with high regioregularity, precise molecular weight, and narrow molecular weight distribution. The product is convertible into sequence-regulated substituted polyacetylene by oxidative dehydrogenation using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). Block copolymers containing polyacetylene segment are also prepared. Owing to the versatility of the anionic reactions, the present strategy can serve as a powerful tool of precise control on polymer chain microstructure, architecture, and functionalities in the same time.

Aminobisphosphonate Polymers via RAFT and a Multicomponent Kabachnik-Fields Reaction

Polyacrylamides containing pendant aminobisphosphonate groups are synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization and a multicomponent postpolymerization functionalization reaction. A Moedritzer-Irani reaction installs the phosphonic acid groups on well-defined, RAFT-generated polymers bearing a pendant amine. An alternate route to the same materials is developed utilizing a three-component Kabachnik-Fields reaction and subsequent dealkylation. Kinetics of the RAFT polymerization of the polymer precursor are studied. Successful functionalization is demonstrated by NMR and FTIR spectroscopy and elemental analysis of the final polymers.

From drug to adhesive: a new application of poly(dihydropyrimidin-2(1H)-one)s via the Biginelli polycondensation

Poly(dihydropyrimidin-2(1H)-one)s can be synthesizedviathe Biginelli polycondensation in a short time. Thein situBiginelli polycondensation could glue two metal sheets together.

Enhanced reactivity of dendrons in the Passerini three-component reaction

An unexpected substituent effect that accelerates Passerini reactions in THF has enabled the synthesis of three generations of dendrimers.

Homopolymer bifunctionalization through sequential thiol–epoxy and esterification reactions: an optimization, quantification, and structural elucidation study

In this study, we probe various aspects of a post-polymerization double-modification strategy involving sequential thiol–epoxy and esterification reactions for the preparation of dual-functional homopolymers.

Dual side chain control in the synthesis of novel sequence-defined oligomers through the Ugi four-component reaction

The synthesis of sequence-defined oligomers by the iterative application of the modular Ugi four-component reaction (U-4CR) and the efficient thiol–ene addition reaction is described.

Polymerization and degradation of aliphatic polyesters synthesized by atom transfer radical polyaddition

By tuning leaving group affinity, the aliphatic polyesters synthesized by ATRPA can avoid lactonization and obtain high molecular weights.

Multicomponent isocyanide-based synthesis of reactive styrenic and (meth)acrylic monomers and their RAFT (co)polymerization

A combination of the Passerini reaction and RAFT polymerization is used to produce novel (co)polymers carrying double bond, protected triple bond, protected alcohol, pentafluorophenyl, and diene side group functionality.

Preparation of a Library of Poly(N-sulfonylimidates) by Cu-Catalyzed Multicomponent Polymerization

Efficient synthesis of polyimidates has been a great challenge because of the difficulty of imidate bond formation and limited substrate scope. Here, we describe a successful method for the synthesis of various poly(N-sulfonylimidates) using Cu-catalyzed multicomponent polymerization (MCP). Minimizing water contamination in the polymerization, which results in low-molecular-weight oligomers, allows various combinations of three types of monomers (diynes, sulfonyl azides, and diols) that are bench stable and readily accessible, providing access to a library of polyimidates. Moreover, the formation of polyimidates is highly selective over the conventional click reactions. Most importantly, this report demonstrates a successful MCP that overcomes the drawbacks of previous MCP methods showing narrow monomer scope and producing low-molecular-weight polymers.