The combination of living radical polymerization and click chemistry for the synthesis of advanced macromolecular architectures

Since its introduction, click chemistry has received a considerable amount of interest. In this contribution, the term click chemistry and the reactions that fall under this term are briefly explained. The main focus of this review is on the application of click chemistry in conjunction with living radical polymerization for the synthesis of advanced macromolecular architectures. Therefore the most powerful living radical polymerization (LRP) techniques are discussed and an overview of click chemistry in the different synthetic schemes is given. A large number of examples are shown that include the synthesis of block copolymers, star-shaped polymers, surface modified particles, and polymer-protein conjugates. The enormous potential of LRP/click chemistry is probably best exemplified by the synthesis of different miktoarm star copolymers, to which a separate section is dedicated.     

Reversible modification of oligodeoxynucleotides: click reaction at phosphate group and alkali treatment

We characterized click reaction between oligodeoxynucleotides (ODNs) possessing acetylene groups at the phosphate unit and azide compounds. Cu(I)-catalyzed cycloaddition proceeded efficiently to form the corresponding functional ODNs. The resulting ODNs could be converted into ordinary ODNs by treatment with aqueous methylamine. The present method successfully achieved a reversible modification of ODNs.     

Towards click chemistry: Multicomponent reactions via combinations of name reactions

In this report, we try to show the importance of incorporation of name reactions in the sequential cascade reaction in which significantly decreasing the number of steps towards an ideal and practical multi-step synthesis of natural products as well showing virtually all the advantages already mentioned for “Click Chemistry”. In addition, since the chiral inductions are desired for most of these sequential name reactions, their asymmetric catalyzed reactions were also described.     

The ‘inverse electron-demand’ Diels-Alder reaction in polymer synthesis. Part 5: Preparation and model reactions of some electron-rich bis-dienamines

The m- and p-phenylene-bridged bis-azolopyridinium salts have been synthesized and converted into the corresponding bis-dienamines by reaction with pyrrolidine. These dienamines react readily with dimethyl 1,2,4,5-tetrazine-dicarboxylate to yield the bis-azolylvinyl-pyridazines.     

Adding diversity to ruthenium(II)-arene anticancer (RAPTA) compounds via click chemistry: The influence of hydrophobic chains

The application of click chemistry to develop libraries of organometallic ruthenium-arene complexes with potential anticancer properties has been investigated. A series of ruthenium-imidazole-triazole complexes, with hydrophobic tails, were prepared from a common precursor via click chemistry. The tail could be attached to the ligand prior to coordination to the ruthenium complex or following coordination, the former giving the product in superior yield. The complexes were screened for cytotoxicity in tumourigenic and non-tumourigenic cell lines, and while the compounds were only moderately cytotoxic, good selectivity for tumourigenic cells was observed.     

Precisely controlled copper(0)‐catalyzed one‐pot reaction: Concurrent living radical polymerization and click chemistry

Copper(0)‐catalyzed one‐pot reaction combining living radical polymerization and “click chemistry” was investigated. By precisely tuning reaction time, three novel well‐defined polymers with different degree of carboxyl substitution, poly(propargyl methacrylate) (PPgMA), poly(1‐(4‐carboxyphenyl)‐[1,2,3]triazol‐4‐methyl methacrylate) (PCTMMA), and poly(1‐(4‐carboxyphenyl)‐[1,2,3]triazol‐4‐methyl methacrylate‐co‐propargyl methacrylate) (PCTMMA‐co‐PPgMA) were selectively obtained via Cu(0) powder/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) cocatalyzed LRP and click chemistry. In addition, gel permeation chromatography and ¹H NMR analysis in conjunction with FTIR spectroscopy elucidate that one‐pot process undergoes three steps due to a pronounced rate enhancement of click reaction: (1) generating new monomer, 1‐(4‐carboxyphenyl)‐[1,2,3]triazol‐4‐methyl methacrylate (CTMMA); (2) copolymerization of two monomers (CTMMA and PgMA); (3) building homopolymer PCTMMA. Surprisingly, in contrast to typical Cu(I)‐catalyzed atom transfer radical polymerization (ATRP), copper(0)‐catalyzed one‐pot reaction showed high carboxylic acid group tolerance. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and self-assembly of pH-responsive amphiphilic dendritic star-block terpolymer by the combination of ROP, ATRP and click chemistry

Novel pH-responsive amphiphilic dendritic star-block poly(l-lactide)-b-poly(2-(N, N-diethylamino)ethyl methacrylate)-b-poly(ethylene oxide) (DPLLA-b-PDEAEMA-b-PEO) terpolymers were synthesized by the combination of ring-opening polymerization (ROP), atom transfer radical polymerization (ATRP), and click chemistry. DPLLAOH was synthesized by ROP of l-lactide (LLA) and then reacted with propargyl 3-carboxylic-propanoate to obtain alkynyl-DPLLA. PEO-b-PDEAEMA-Br was prepared by ATRP of DEAEMA and then reacted with NaN₃ to obtain PEO-b-PDEAEMA-N₃. DPLLA-b-PDEAEMA-b-PEO was easily prepared by click chemistry of alkynyl-DPLLA and PEO-b-PDEAEMA-N₃. DPLLA-b-PDEAEMA-b-PEO can assemble into micelles in water with PLLA segments as core and PEO segments as corona. The hydrophilicity/hydrophobicity of PDEAEMA can be adjusted with the alteration of pH values. Therefore, PDEAEMA segments form core or corona of micelles at pH ? 7 or pH < 7. Due to the pH-responsive property of PDEAEMA and unique structure of terpolymer, the size and conformation of the micelles can be changed to some extent by altering the pH values of solutions.     

Microwave-assisted aza-Prins reaction. Part 2: straightforward access to 2,6-disubstituted 1-azaadamantanes

Novel symmetrically and unsymmetrically disubstituted 1-azaadamantanes were prepared as a single, chiral diastereomer via double microwave-assisted aza-Prins cyclization in one-pot or sequential reaction format.     

Intramolecular Diels-Alder reaction of 1-aminoisobenzofurans: Application to the synthesis of benzo[c]phenanthridines

Intramolecular Diels-Alder reactions of 1-aminoisobenzofurans give benzo[c]phenanthridines. The reactive intermediates are generated from o-(diazomethyl)benzamides.     

Tandem furo[3,4-b]pyridine formation—Diels-Alder reaction: an approach to the synthesis of nitrogen containing heterocyclic analogues of 1-arylnaphthalene lignans

The coupling of Fischer carbene complexes with 2-alkynyl-3-pyridine carbonyl derivatives has been examined. The reaction affords furo[3,4-b]pyridine as transient intermediates; the latter undergo [4+2] cycloaddition with an electron-deficient dienophile. Acid/base-induced ring opening of the exo-cycloadducts followed by aromatization give substituted quinolines related to heterocyclic analogues of 1-arylnaphthalene lignans. An intramolecular variant of this protocol is also feasible with use of unactivated alkenyl tethers; however, the bridged cycloadducts are unisolable as they undergo spontaneous ring opening to yield alcohol. This method is also useful for the in situ generation of the furo[3,4-b]quinoline intermediate for the first time, which can be trapped with dienophiles.     

Photochemical tuning of materials: A click chemistry perspective

Light driven reactions are perpetual tools for environment sustainability. As an external trigger, most of the photon driven reactions are stereoselective, precise, efficient and offer temporal control for biomolecules. The photoinduced reactions are key to unique molecular transformations that include click and unclick reactions. Since 2003, there has been an exponential rise research papers citing light driven reactions. This review considers the light promoted development and modification of reactions that fall under the criteria of ‘Click’ series of transformations. The review lays emphasis on the light induced biochemical, carbohydrate modification, surface labelling, bioconjugation, polymer modification, dendrimer synthesis, [4 + 2] and [2 + 2] reaction, thiol–ene/yne coupling, Cu assisted cycloaddition, strain-promoted azide alkyne cycloaddition (SPAAC), nitro photoclick and photounclick reactions published in last one and half decade. This series of photoclick reactions use short wavelength radiations and are instant, clean, and near to perfect for transforming reactants to the desirable products.     

Diels-Alder addition of some 6-and 5-member ring aromatic compounds on the Si(001)-2×1 surface: dependence of the binding energy on the resonance energy of the aromatic compounds

An energy decomposition scheme is proposed for understanding of the relative low binding energy of the [4+2] cycloaddition of benzene on the Si(001)-2×1 surface. By means of density functional cluster model calculations, this scheme is demonstrated to be applicable to some other 6- and 5-member ring aromatic compounds, giving a trend that the binding energy of the [4+2] cycloaddition products of those aromatic compounds on the Si(001) surface depends strongly on their resonance energy.     

Synthesis of N-propynyl analogues of peptide nucleic acid (PNA) monomers and their use in the click reaction to prepare N-functionalized PNAs

Application of the click reaction for coupling a 2-(2-aminoethoxy)ethoxy (AEE) function to thyminyl, cytosinyl and adeninyl peptide nucleic acid (PNA) monomer analogues bearing a N-propynyl group, in place of the original N-2-aminoethyl moiety, has been explored. The N-propynyl PNA analogues were prepared from glycine ethyl ester hydrochloride and the structure of the thyminyl derivative was confirmed by X-ray diffraction. These monomers were employed in click reactions with Boc-protected AEE azide to afford the corresponding triazolyl-linked PNA-AEE conjugates in yields ranging from 64 to 76%. [1,4]-Regiochemistry was verified from a NOESY correlation experiment.     

Kinetics and mechanism of triethylamine-catalyzed 1,3-proton shift: Optimized and substantially improved reaction conditions for biomimetic reductive amination of fluorine-containing carbonyl compounds

Kinetic study of the triethylamine (TEA)-catalyzed isomerization of imine, derived from benzylamine and trifluoroacetophenone to the corresponding N-benzylidene-2,2,2-trifluoro-1-(phenyl)ethylamine has revealed concerted nature of the mechanism of this reaction via a virtually unionized transition state. As a synthetic bonus of this kinetic study, we found that application of a polar solvent (acetonitrile) and four equivalents of TEA provide for optimal reaction conditions at high concentrations. We demonstrate that application of these reaction conditions allows to substantially increase the reaction rates, chemical yields and results in cleaner formation of the target products.     

Statistical decision theory applied to analytical chemistry : Part 1. The statistical decision model and its relation to branches of mathematical statistics

Statistical decision theory can be considered as an extension of point estimation, interval estimation and hypotheses testing. Basic elements of statistical decision models are discussed and the relation between decision theory and other branches of mathematical statistics is indicated. Some illustrative examples of application to analytical chemistry are given.     

Design and synthesis of novel type VI-like β-turn mimetics. Diversity at the i+1 and the i+2 position

In this paper, a synthetic approach for functionalised 5-aminopiperidinone-2-carboxylate (APC) systems as non-pro cis-peptide bond containing external β-turn mimics is presented. The scope and limitations of the synthetic method are discussed and the potential turn inducing properties of a model compound are evaluated by means of molecular modelling and NMR analysis.     

Metallaborane reaction chemistry. Part 12. Some interactions of acetylenes and isocyanides with selected metallaboranes

Compared to the chemistry associated with the basic syntheses and structures of the metallaboranes, their reaction chemistry is relatively uninvestigated. To illustrate the potential variety of such reaction chemistry, a linked overview of some previously reported and previously unreported reactions of the nido-6-metalladecaboranes [(PPh₃)₂HIrB₉H₁₃], [(PPh₃)(Ph₂PC₆H₄)HIrB₉H₁₂], [(η⁶-C₆Me₆)RuB₉H₁₃], [(η⁶-MeC₆H₄^isoPr)RuB₉H₁₃] and [(η⁵-C₅Me₅)RhB₉H₁₃] with acetylenes and isocyanides is presented, together with some related chemistry derived from the arachno-type 4-metallanonaboranes [(PMe₂Ph)₂PtB₈H₁₂] and [(PMe₃)₂(CO)HIrB₈H₁₂]. Reductions, oligomerisations, and reductive oligomerisations of the unsaturated species are observed, as well as complete or partial incorporation of carbon and nitrogen hetero atoms into the metallaborane clusters.¹     

Synthesis of vinca alkaloids and related compounds. Part 110: A new synthetic method for the preparation of pandoline-type alkaloid-like molecules

A practicable synthesis of a pandoline-type alkaloid-like molecule is reported through an efficient preparation of carbinolamine ether intermediates (9a and 9b). The key step of the synthesis consists of an intramolecular cycloaddition of the secodine-type intermediate (2), which was formed from the tryptamine derivative (3) and lactol (4). The mechanism of the cycloaddition reaction was investigated by quantum chemical calculations and it was found to follow a step-wise mechanism involving a zwitterionic intermediate (15). By employing this strategy, other members of the family of pandoline alkaloids or alkaloid-like molecules could be synthesized by reacting the tryptamine derivative with appropriately functionalized aldehydes.