1.3-Dipolare Cycloadditionen Rückschau und Ausblick

Versatile Two-Step Functionalization of Nanocarbons: Grafting of Propargylic Groups and Click Post-Functionalization

Chemical functionalization of nanocarbons is essential for further applications in various fields. We developed a facile, inexpensive, and gram‐scale one‐pot route towards alkynyl‐functionalized nanocarbons. Nucleophilic addition/propargylic capture places alkyne moieties at the surface of carbon nanotubes (CNTs) and graphene. Thermogravimetric analysis coupled with mass spectrometry and Raman analysis confirmed the efficiency of this process. Conductivity measurements demonstrated the maintenance of the CNT electrical properties. The attached alkynyl moieties were reacted with various azide derivatives through the click‐Huisgen [3+2] cycloaddition and characterized with XPS. The efficient addition of those derivatives enables the application of our finding in various fields. This route is a reliable and convenient alternative to the known diazonium functionalization and oxidation‐esterification reactions to graft alkyne groups.

Ultrasound-promoted organocatalytic enamine-azide [3 + 2] cycloaddition reactions for the synthesis of ((arylselanyl)phenyl-1H-1,2,3-triazol-4-yl)ketones

The use of sonochemistry is described in the organocatalytic enamine-azide [3 + 2] cycloaddition between 1,3-diketones and aryl azidophenyl selenides. These sonochemically promoted reactions were found to be amenable to a range of 1,3-diketones or aryl azidophenyl selenides, providing an efficient access to new ((arylselanyl)phenyl-1H-1,2,3-triazol-4-yl)ketones in good to excellent yields and short reaction times. In addition, this protocol was extended to β-keto esters, β-keto amides and α-cyano ketones. Selanyltriazoyl carboxylates, carboxamides and carbonitriles were synthesized in high yields at short times of reaction under very mild reaction conditions.

Collagen-Like Peptide Bioconjugates

Collagen-like peptides (CLPs), also known as collagen-mimetic peptides (CMPs), are short synthetic peptides that mimic the triple helical conformation of native collagens. Traditionally, CLPs have been widely used in deciphering the chemical basis for collagen triple helix stabilization, mimicking collagen fibril formation and fabricating other higher-order supramolecular self-assemblies. While CLPs have been used extensively for elucidation of the assembly of native collagens, less work has been reported on the use of CLP-polymer and CLP-peptide conjugates in the production of responsive assemblies. CLP triple helices have been used as physical cross-links in CLP-polymer hydrogels with predesigned thermoresponsiveness. The more recently reported ability of CLP to target native collagens via triple helix hybridization has further inspired the production of CLP-polymer and CLP-peptide bioconjugates and the employment of these conjugates in generating well-defined nanostructures for targeting collagen substrates. This review summarizes the current progress and potential of using CLPs in biomedical arenas and is intended to serve as a general guide for designing CLP-containing biomaterials.

Conjugatable and Bioreduction Cleavable Linker for the 5'-Functionalization of Oligonucleotides

An efficient conjugatable and bioreduction cleavable linker was designed and synthesized for the 5'-terminal ends of oligonucleotides. A phosphoramidite reagent bearing this linker was successfully applied to solid phase synthesis and incorporated at the 5'-terminal ends of oligonucleotides. The controlled pore glass (CPG)-supported oligonucleotides were subsequently conjugated to a diverse range of functional molecules using a CuAAC reaction. The synthesized oligonucleotide conjugates were then cleaved using a nitroreductase/NADH bioreduction system to release the naked oligonucleotides.

Sonochemistry in organocatalytic enamine-azide [3+2] cycloadditions: A rapid alternative for the synthesis of 1,2,3-triazoyl carboxamides

We described herein the use of sonochemistry in the organocatalytic enamine-azide [3+2] cycloadditions of β-oxo-amides with a range of substituted aryl azides. These sonochemical promoted reactions were found to be amenable to a range of β-oxo amides or aryl azides, providing an efficient access to new N-aryl-1,2,3-triazoyl carboxamides in good to excellent yields and short times of reaction.

Enantioselective magnesium-catalyzed transformations

This review updates the major progress in the field of enantioselective transformations promoted by chiral magnesium catalysts, covering the literature since 2007, illustrating the power of these green catalysts to promote many types of reactions.

Enantioselective Silver-Catalyzed Transformations

This review collects the major progress in the field of enantioselective transformations promoted by chiral silver catalysts, covering the literature since 2008, well illustrating the power of these especially mild Lewis acid catalysts to provide novel asymmetric reactions.

Synthesis and facile end-group quantification of functionalized PEG azides

Azido-functionalized poly(ethylene glycol) (PEG) derivatives are finding ever-increasing applications in the areas of conjugation chemistry and targeted drug delivery by their judicious incorporation into nanoparticle-forming polymeric systems. Quantification of azide incorporation into such PEG polymers is essential to their effective use. 1H Nuclear Magnetic Resonance (NMR) analysis offers the simplest approach; however, the relevant adjacent azide-bearing methylene protons are often obscured by the PEG manifold signals. This study describes the synthesis of 1,2,3-triazole adducts from their corresponding PEG azides via a convenient, mild click reaction, which facilitates straightforward NMR-based quantitative end-group analysis.This method was found to be compatible with many examples of bifunctional azido PEGs with molecular weights ranging from 2 to 18 kDa bearing a variety of functional groups. © 2016 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2888-2895.

Synthesis of Organofluoro Compounds Using Methyl Perfluoroalk-2-ynoates as Building Blocks

This review provides an overview of several synthetic applications of methyl perfluoroalk-2-ynoates, leading to convenient preparation of many perfluoroalkylated compounds. The use of these important substrates in the synthesis of various five-, six-, and seven-membered heterocycles, cyclopentadienes, and biphenyls is described, alongside a discussion of the mechanistic aspects of these reactions.

A Cu-free clickable fluorescent probe for intracellular targeting of small biomolecules

We synthesized a novel cyclooctyne-based clickable fluorescent probe with versatile properties such as high cell-membrane permeability and free diffusibility in the cell. Our probe "FC-DBCO" was conjugated to an azide-modified mannose via a Cu-free click reaction in living HeLa cells and displayed intracellular specific fluorescence imaging with low background signals.