Hexavanadate Functionalization With Methacrylic Moieties via “Click” Chemistry: An Elegant Route to Metalorganic Vinyl Monomers

Copper(I) is able to catalyze Huisgen 1,3-dipolar cycloaddition in a "click" fashion. This copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction presents excellent chemoselectivity and occurs over a wide-range of reaction conditions. It shows tolerance to variation in both pH and solvent polarity, thereby facilitating the ligation of peptides and proteins to produce peptidomimetics and synthetic proteins. In addition, the only product formed is a 1,4-disubstituted-1,2,3-triazole moiety, in many aspects resembling the natural peptide bond, including hydrogen-bonding capability, planarity, distance between the 1 and 4 substituents, and conformational restriction of the peptide backbone; thus the triazole-backbone-modified peptide, in which a triazole replaces the amide bond, may be anticipated to present a secondary structure similar to that of its natural counterpart. This Focus Review describes the scope and applications of copper(I)-catalyzed alkyne–azide cycloaddition in synthetic peptide/protein chemistry.

Cu(I)-catalyzed click reaction, a set of powerful and virtually reliable 1,3 dipolar cycloaddition of organic azide and terminal alkyne, has been extensively used in adjoining two entirely different building blocks, enabling an easy access of complex molecular-level architectures, which find exponentially expanding application in diverse disciplines of science ranging from organic synthesis, material sciences, combinatorial chemistry to medicinal chemistry and chemical biology. This highly efficient and reliable protocol has several distinct advantages, the most notable are, its high chemoselectivity, excellent regioselectivity, tolerance to a variety of solvents and functional groups, mild and compatible reaction conditions etc., which address this approach as a straightforward way of establishing covalent connections between different molecules containing various functionalities. Compatibility of Cu(I)-catalyzed azide alkyne cycloaddition (CuAAC) reaction with carbohydrate chemistry has led to the development of biologically relevant molecules and diverse neoglycoconjugates and neoglycopolymers. This review highlights the extensive application of the click reaction in carbohydrate chemistry for drug discovery, bioconjugaion study, and for the generation of various simple to complex glycoconjugates such as glycopeptides, polysaccharides, glyco-macrocycles, glyco-arrays, glyco-dendrimers, glyco-clusters and glycopolymers etc., having targeted functional properties and future scope in various branches of science.

Free-radical polymerization inside mesoporous silica has been investigated in order to open a route to functional polymer-silica composite materials with well-defined mesoporosity. Various vinyl monomers, such as styrene, chloromethyl styrene, 2-hydroxyethyl methacrylate, and methacrylic acid, were polymerized after impregnation into mesoporous silicas with various structures, which were synthesized using polyalkylene oxide-type block copolymers. The location of the polymers was systematically controlled with detailed structures of the silica framework and the polymerization conditions. Particularly noteworthy is the polymer-silica composite structure obtained by in situ polymerization after the selective adsorption of monomers as a uniform film on silica walls. The analysis of XRD data and the N(2) adsorption isotherms indicates the formation of uniform polymer nanocoating. The resultant polymer-silica composite materials can easily be post-functionalized to incorporate diverse functional groups in high density, due to the open porous structure allowing facile access for the chemical reagent. The fundamental characteristics of the composite materials are substantiated by testing the biomolecule's adsorption capacity and catalytic reactivity. Depending on the structure and composition of polymers, the resultant polymer-silica composite materials exhibit notably distinct adsorption properties toward biomolecules, such as proteins. Furthermore, it is demonstrated that the nanocoatings of polymers deposited on the mesopore walls have remarkably enhanced catalytic activity and selectivity, as compared to that of bulk polymer resins. We believe that, due to facile functionalization and attractive textural properties, the mesoporous polymer-silica composite materials are very useful for applications, such as adsorption, separation, host-guest complexes, and catalysis.

Two-step degradable ABAC-type periodic poly(cyclic acetal)s synthesized by sequence-programmed monomer formation and subsequent polyaddition based on cyclotrimerization of one vinyl monomer and two aldehydes

Preparation of vinylgermanes and a germole by the Pd-catalyzed reactions of Me(in3)GeCn with acetylenes

A convenient synthetic strategy has been designed to prepare an alkyne-modified synthon for automated DNA synthesis. It is based on the key O-DMTr-protected 4-(2-hydroxyethyl)morpholin-2,3-dione and building blocks obtained by its functionalization by various aliphatic amines. A respective nonnucleosidic phosphoramidite monomer containing a terminal alkyne in the side-chain was synthesized, and corresponding oligothymidylates incorporating the modification in various positions were prepared. The presence of the alkyne group was confirmed by Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) between the functionalized oligonucleotide and an azide derivative of 7-nitro-2,1,3-benzoxadiazole.

Boosting CO2 Conversion with Terminal Alkynes by Molecular Architecture of Graphene Oxide-Supported Ag Nanoparticles

Polymerization of surface-active monomers: 7. Radical copolymerizations of anionic surface-active monomer, sodium di(10-undecenyl)sulfosuccinate, with electron-accepting monomers and vinyl monomers in micellar and isotropic solutions

An effective method for the synthesis of the rotaxane cross-linked polymers (RCPs) was developed using a metal-containing supramolecular cross-linker (MSC). Radical polymerization of several vinyl monomers and bulky end-capped comonomer afforded RCPs in high yields. The obtained RCPs exhibited thermal properties corresponding to their respective polymer skeletons. Swelling ratio gradually increased with the decreasing amount of the steric comonomer units, indicating that the sliding ability of the movable cross-linker is strongly related to the swelling ability.

Alkynes are one of the most abundant chemicals in organic chemistry, and therefore the development of catalytic reactions to transform alkynes into other useful functionalities is of great value. In recent decades, extraordinary advances have been made in this area with transition-metal catalysis, and silver-based reagents are ideal for the activation of alkynes. This high reactivity is probably due to the superior π-Lewis acidic, carbophilic behavior of silver(I), allowing it to selectively activate carbon-carbon triple bonds (C≡C) through the formation of a silver-π complex. Within this field, we have been interested in the activation and subsequent reactions of readily accessible terminal alkynes for the synthesis of nitrogen-containing compounds, which has generally received less attention than methods involving internal alkynes. This is possibly due to the lack of suitable reactive reaction partners that are compatible under transition metals. Therefore, a thorough understanding of the factors that influence homogeneous silver catalysis and the identification of the appropriate reaction partners can provide a powerful platform for designing more efficient silver-catalyzed reactions of terminal alkynes. In this context, we envisioned that using readily available, environmentally benign, and inexpensive trimethylsilyl azide (TMSN3) or an isocyanide as the nitrogen-donor would be the key to develop novel reactions of terminal alkynes.This Account describes our efforts since 2013 toward the development of novel silver-catalyzed tandem reactions of terminal alkynes with either TMSN3 or isocyanides for the assembly of various nitrogen-containing compounds. The first section of this Account discusses the initial developments in the silver-catalyzed hydroazidation of terminal alkynes with TMSN3 and the subsequent advances made in our laboratory. We first describe the discovery and experimental and computational mechanistic investigations of silver-catalyzed hydroazidation reactions, which is the most efficient strategy reported to date for accessing vinyl azides. Mechanistic study of this hydroazidation reaction provides an alternative activation mode for terminal alkyne conversion in transition metal catalysis. We then present the chemistry of in situ generated vinyl azides, including one-pot tandem radical addition/cyclization or migration reactions of terminal alkynes to access a variety of nitrogen-containing molecules. Finally, we discuss the one-pot, multistep tandem hydroazidation and 1,2-azide migratory gem-difluorination of terminal alkynes for the synthesis of β-difluorinated alkyl azides. The second section describes the silver-catalyzed coupling reactions between terminal alkynes and isocyanides, which offer a straightforward method for accessing synthetically useful building blocks, such as pyrroles, allenamides, benzofuran, vinyl sulfones, indazolines, propiolonitriles, and pyrazoles. The high efficiency, mild conditions, low cost, broad substrate scope, high chemo- and regioselectivity, step economy, and ecofriendliness of the developed approaches make them attractive and practical. The progress in this area provides guiding principles for designing new reactions of terminal alkynes that can be extended to various nitrogen-containing molecules of interest to medicinal and materials chemists.

Transition-metal-catalysed asymmetric multicomponent reactions with two similar substrates often suffer from the lack of strategies to control the chemo-, regio-, and stereoselectivity of these substrates due to the close similarity in the chemical structures and properties of each reagent. Here, we describe a Cu(I)-catalysed asymmetric radical 1,2-carboalkynylation of two different terminal alkynes and alkyl halides with high chemo-, regio-, and stereoselectivity by using sterically bulky chiral tridentate anionic N,N,P-ligands and modulating alkynes with different electronic properties to circumvent above-mentioned challenges. This method features good substrate scope, high functional group tolerance of two different terminal alkynes, and diverse alkyl halides, providing universal access to a series of useful axially chiral 1,3-enyne building blocks.

Large screening of DNA-compatible reaction conditions for Suzuki and Sonogashira cross-coupling reactions and for reverse amide bond formation

For Abstract see ChemInform Abstract in Full Text.

Rare-earth silylamide complex, Y[N(SiMe3)2]3, was found to exhibit good catalyst activities for regio- and stereoselective dimerization of terminal aliphatic and aromatic alkynes in the presence of amine additives. Thus, using tertiary amine additives, particularly N(SiMe3)3, aliphatic terminal alkynes were efficiently converted to head-to-tail dimers. On the other hand, only Z-head-to-head dimers were obtained in high yields from aromatic alkynes with the catalyst and aromatic primary amines such as 4-ClC6H4NH2.

A Mn(I)‐catalyzed chelation‐assisted direct C6−H alkenylation of 2‐pyridones with both terminal and internal alkynes in a highly regio‐ and stereo‐selective manner has been developed. The catalytic system consisting of Mn(CO)5Br catalyst and KOAc additive allows 1‐(2‐pyridyl)‐2‐pyridones to undergo alkenylation with various terminal alkynes in methyl tert‐butyl ether (MTBE) to furnish the C6‐alkenylated 2‐pyridone products in high yields, and the alkenylation with internal alkynes occurs in CH2Cl2 at increased catalyst and additive loadings. Mechanistic studies suggest the involvement of a five‐membered organomanganese as the key intermediate in the catalytic cycle.magnified image