Surface-Modified Superparamagnetic Iron-Oxide Nanoparticles

Summary. The generation of superparamagnetic iron-oxide nanoparticles bearing fluorescent ligands is described. γ-Fe₂O₃ nanoparticles (radius ∼4 and 8 nm) bearing octylamine or oleic acid as ligands were prepared by hydrothermal synthesis starting from Fe-cupferron and iron pentacarbonyl, respectively. Ligand exchange proceeds with 1,2-diols bearing ω-azido or ω-bromo ligands at elevated temperatures. Subsequent nucleophilic substitution reaction, followed by 1,3-dipolar cycloaddition reactions with 2,4,6-trinitro-1-O-propargyl-benzene yields superparamagnetic iron-oxide nanoparticles with a fluoresecent ligand on their surface.     

Synthesis of Surface-Modified Nanoparticles via Cycloaddition-Reactions

The surface modification of nanoparticles via azide/alkine-1,3-dipolar cycloaddition-reactions is described. Ligand exchange onto various nanoparticles was monitored by ¹H NMR spectroscopy and formed the basis for the attachment of ligands onto the nanoparticles and their subsequent modification by dipolar cycloaddition reactions. Nanoparticle-surfaces were monitored by binding onto self-assembled monolayers derivatized with matching supramolecular interactions after derivatization.     

Cross-Section Molecular Imaging of Supramolecular Microtubes with Contact Atomic Force Microscopy

Bent molecules, distorted layers, columnar domains, and tube membranes (shown schematically in the picture): These hierarchical layers were directly visualized by contact atomic force microscopy along the long axes of the molecules aligned within microtubes made up of bolaamphiphile 1 by self-assembly.     

Synthesis of ethyl 3-phenyl-4-(trifluoromethyl)isoxazole-5-carboxylate via regioselective dipolar cycloaddition

Efforts to prepare ethyl 3-phenyl-4-(trifluoromethyl)isoxazole-5-carboxylate (1) by developing a regioselective 1,3-dipolar cycloaddition between phenyl nitrile oxide and various 4,4,4-trifluoromethyl crotonates are described. The substitution at the C2-position of crotonate dipolarophile 4 significantly influenced the regiochemistry and yield of the cycloaddition. Enol and enol ether-based crotonates underwent regioselective cycloadditions with phenyl nitrile oxide to provide 4-trifluoromethyl isoxazoles in good yields.     

Synthesis of new calix[4]pyrrole derivatives via 1,3-dipolar cycloadditions

Octamethylcalix[4]pyrrole-2-carbaldehyde 1 and 3-(octamethylcalix[4]pyrrol-2-yl)propenal 5 were used as precursors of azomethine ylides, which were trapped in situ with a range of dipolarophiles, such as 1,4-benzoquinone, 1,4-naphthoquinone, and fumaronitrile. Aldehyde 1 showed very low reactivity but the azomethine ylide generated from the reaction of aldehyde 5 with N-methylglycine could be trapped with those dipolarophiles to afford new β-substituted octamethylcalix[4]pyrrole derivatives in moderate yields. The resulting cycloadducts show high affinity constants for fluoride and acetate anions; compounds 7 and 8 display sharp changes in color in the presence of these anions.     

Tricyclic-isoxazolidine analogues via intramolecular 1,3-dipolar cycloaddition reactions of nitrones

The tricyclic-isoxazolidine analogues tetrahydrothiochromenoisoxazoles, hexahydroisoxazolequinolines and tetrahydroisoxazolepyranopyridines were prepared by an intramolecular 1,3-dipolar cycloaddition reaction of a nitrone with an alkene. For N-alkylated hexahydroisoxazolequinolines, reduction of the reaction time from two days to 40 min was achieved using microwave heating. The cyclization to form tetrahydroisoxazolepyranopyridines only proceeded when the alkene was substituted with an electron withdrawing group.     

Synthesis of pyrimidine-containing 3-aminobutenolides

An efficient synthesis of pyrimidine-containing butenolides is reported, starting from C-alkoxycarbonyl isoxazolidines. Two competitive reaction routes are operating: the pathway leading to homo-N,O-nucleosides, based on the reduction of an ester group at C₃, and the reaction channel leading to butenolides promoted by the removal of the hydrogen atom at C₃. The two reaction pathways can be easily controlled according to the adopted experimental conditions     

表面修饰ZrO_2纳米微粒的合成及结构表征(英文)

在溶液中化学合成了硬脂酸修饰ZrO2 纳米微粒 ,采用XRD、TEM和EA表征了ZrO2 纳米微粒的结构 ,结果表明成功合成了表面包覆硬脂酸分子的ZrO2 纳米微粒。     

Synthesis of modified triazole nucleosides possessing one or two base moieties via a click chemistry approach

Copper-catalyzed 1,3-dipolar cycloaddition of propargyl and azidoethyl thymine and adenine derivatives afforded triazole nucleosides bearing one or two base moieties. A catalytic role of the adenine nucleus was observed and is explained through copper-adenine coordination in the intermediate copper acetylide-azide complex. The antioxidant activity of the obtained cycloadducts was tested.     

Synthesis of polyfluorophenyl substituted-4,5-dihydropyrazole derivatives via 1,3-dipolar cycloaddition of nitrile imine with ethyl acrylate

Oxidation of aldehyde 4-chloro-2,3,5,6-tetrafluorophenylhydrazones (1) with [bis(acetoxy)iodo]benzene leads to the formation of nitrile imines (2) which reacted in situ with ethyl acrylate to produce 3-substituted-1-(4-chloro-2,3,5,6-tetrafluorophenyl)-5-ethoxycarbonyl-4,5-dihydropyrazoles (3) in moderate to good yields. The structures of new compounds were fully confirmed by their spectral data, elemental analyses and X-ray diffraction (XRD) analysis. A plausible reaction mechanism for the synthesis of title compounds is presented.     

Synthesis of pyrrolidine ring-fused metallofullerene derivatives

The azomethine ylide generated from the reaction of sarconsine and formaldehyde adds to Gd@C₈₂ to give the mono- through octo-adducts, while the direct interaction of sarcosine with Gd@C₈₂ yields only the mono-adduct, which is characterized by HPLC, MALDI-TOF MS, UV-Vis-NIR and FT-IR. The reaction mechanism for this reaction is proposed to be a 1,3-dipolar addition.     

Surface Modification and Functionalization of Metal and Metal Oxide Nanoparticles by Organic Ligands

Summary. Metal or metal oxide nanoparticles possess unique features compared to equivalent larger-scale materials. For applications, it is often necessary to stabilize or functionalize such nanoparticles. Thus, modification of the surface of nanoparticles is an important chemical challenge. In this survey, various possibilities are discussed how nanoparticles can be protected by organic ligands and how these ligands can be used to introduce functionalities. The preparative possibilities include grafting of an already functionalized ligand on the nanoparticle surface, exchanging part or all existing ligands on the nanoparticle surface, or grafting of a ligand on a nanoparticle followed by modification by organic chemical reactions.     

Asymmetric 1,3-dipolar reactions of 3-sulfinylfuran-2(5H)-ones with 11H-dibenzo[b,e]azepine 5-oxide. Synthesis of pyrroloazepines via isoxazoloazepines

The addition of morphanthridine N-oxide (1) to homochiral 3-p-tolylsulfinylfuran-2(5H)-ones (2a and 2b) under mild conditions affords furoisoxazoloazepines (3a and 3b) in high yields and with complete regioselectivity. The π-facial and endo-selectivities are also complete from 2a, which yields anti-3a-endo as the only diastereoisomer, whereas cycloreversion determines that the anti-3b-endo adduct can be almost exclusively isolated from 2b. Proper manipulation of the furoisoxazoloazepines allows the synthesis of the optically pure isoxazoloazepines and pyrroloazepines.     

Synthesis of complex dispirocyclopentanebisoxindoles via cycloaddition reactions of 4-dimethylamino-1-alkoxycarbonylmethylpyridinium bromides with 2-oxoindolin-3-ylidene derivatives

The cycloaddition reactions of 4-dimethylamino-1-alkoxycarbonylmethylpyridinium bromides with various 2-oxoindolin-3-ylidene derivatives in ethanol in the presence of triethylamine afforded the unprecedented dispirocyclopentanebisoxindole derivatives in good yields and in high diastereoselectivity. Under similar reaction conditions, the reactions of 1-alkoxycarbonylmethylpyridinium bromides with 3-phenacylideneoxindoles only resulted in 4-oxo-3-(2-oxoindolin-3-ylidene)-4-arylbutanoates. The stereochemistry of the complex spirooxindoles was established by ¹H NMR data and single crystal structures.     

Synthesis of the tricyclic core structure of vindoline

An efficient synthesis of the core tricyclic structure (18) of vindoline has been achieved using the strategy, which features an intramolecular 1,3-dipolar cycloaddition of the azido dienone (12) to give aziridine (13) with complete region- and stereocontrol.     

Stereoselective Synthesis of Phenyl-1,2,3-triazoles Containing (E)-Vinyl Halide Group via a One-Pot,Three-Component Reaction

Phenyl-1,2,3-triazoles containing (E)-vinyl halide were readily synthesized via a one-pot, three-component reaction of 3-(4- or 2-azidophenyl)acrylic acid, NXS(X=Cl, Br and I) and 1-alkynes in MeCN-H₂O (9:1 v/v) catalyzed by LiOAc/CuI–sodium ascorbate system.

Design and Synthesis of Dumbbell-Shaped POSS-C60 Dyads with Flexible Spacer

Using polyhedral oligomeric silsesquioxane (POSS) as starting material, novel dumbbell-shaped POSS-C₆₀ dyads with flexible spacers were designed and synthesized in good yields by esterification, subsequent etherification, and further 1,3-dipolar cycloaddition of azomethine ylide generated in situ from aldehyde and sarcosine to C₆₀.     

Synthesis and thermal transformations of spiro-fused N-phthalimidoaziridines

Oxidation of N-aminophthalimide in the presence of 2-arylideneinden-1,3-diones with electron-withdrawing substituents gives the corresponding 3-aryl-1-phthalimidospiro[aziridine-2,2′-indene]-1′,3′-diones in good yields. Heating these aziridines with standard dipolarophiles (N-phenylmaleimide, dimethyl acetylenedicarboxylate, maleate, and fumarate) leads, in most cases, to spiro[inden-2,2′-pyrrole] derivatives as products of 1,3-dipolar cycloaddition of the intermediate azomethine ylides with up to 70–95% yields in the case of N-phenylmaleimide. As is typical for 2-acylaziridines, the competing rearrangement into 2-aryl-4H-indeno[2,1-d][1,3]oxazol-4-ones prevails for less active dipolarophiles. Increasing the electron-releasing properties of the 3-aryl ring allows the observation of the push–pull effect of electron-donating and electron-withdrawing substituents on the ease of the three-membered ring-opening.     

Synthesis of novel N-pyridylpyrazole derivatives containing 1,2,4-oxadiazole moiety via 1,3-dipolar cycloaddition and their structures and biological activities

A series of novel 1,2,4-oxadiazole-containing N-pyridylpyrazole derivatives 12a−h were efficiently synthesized with pivaldehyde, pyridylpyrazole carboxylic acid and arylamine as raw materials via 1,3-dipolar cycloaddition. Their structures were identified by melting points, ¹H NMR, ¹³C NMR and elemental analysis or HRMS. The exploration on the single-crystal structures of 12c and 12g revealed the stereochemical and substituent oriental characteristics, and the relevance of the structure and the reaction activity of this type of compounds. The preliminary bioassays indicated that several compounds had good insecticidal activities, among which 12c showed a lethality rate of 80% towards Mythimna separata Walker at 200 μg/mL; some of the compounds exhibited favorable fungicidal activities at 50 μg/mL against Physalospora piricola, Rhizoctonia cereal, Sclerotinia sclerotiorum, etc. Among which, 12a, 12b, 12c and 12h could be considered as new fungicidal leading compounds for further structural optimization. These discoveries along with the structure-activity relationship analysis in this paper will provide useful guidance for the innovative studies on new pyridylpyrazole derivatives and their applications in agrochemical area.     

Synthesis of spiroindene-1,3-dione isothiazolines via a cascade michael/1,3-dipolar cycloaddition reaction of 1,3,4-oxathiazol-2-one and 2-arylidene-1,3-indandiones

The reaction of 1,3,4-oxathiazol-2-one derivative with 2-arylidene-1,3-indandione to furnish novel spiroindene-1,3-dione isothiazoline derivatives by Michael/1,3-dipolar [3+2]-cycloaddition reaction was investigated. The key 1,3-dipolar cycloaddition reaction step was examined in toluene solvent at reflux temperature to obtain mixture of two regioisomers (6a and 6b – 14a and 14b) and single isomers (15–20). The scope of this new reaction was demonstrated with many examples with high reactivity and yields.