Dendrimers based on [1,3,5]‐triazines

A comprehensive and chronological account of dendrimers based on [1,3,5]‐triazines is provided. Synthetic strategies to install the triazine through cycloaddition, cyclotrimerization, and nucleophilic aromatic substitution of cyanuric chloride are discussed. Motivations and applications of these architectures are surveyed, including the preparation of supramolecular assemblies in the solution and solid states and their use in medicines, advanced materials, and separations when anchored to solid supports. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3411–3433, 2006     

Solution proprieties of dendritic triazine/poly(ethylene glycol)/dendritic triazine block copolymers

Dendritic–linear–dendritic triblock copolymers based on poly(ethylene glycol) (PEG) as the core and dendritic triazine blocks were synthesized. The micellar and aggregation characteristics of the compounds were investigated with NMR and fluorescence spectroscopy. The NMR investigations were carried out in a variety of solvents. In those solvents in which both moieties of the linear–dendritic compounds were completely soluble, the NMR spectra of the linear–dendritic compounds were in the normal form, and all of the signals were as expected. However, in other solvents in which one of the moieties of the compounds was not very soluble, the NMR spectra of the compounds were not in the normal form, and some of the signals were broad or disappeared. The results could be related to the aggregation behavior of the block copolymers with extended or packed conformations of PEG in the solvents, as previously observed in similar systems. Also, fluorescence investigations of some of the isolated compounds in aqueous solutions displayed micellar behavior. The critical micelle concentrations of the copolymers were determined with a fluorescence technique. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 28–41, 2005     

Synthesis and luminescence characteristics of conjugated dendrimers with 2,4,6‐triaryl‐1,3,5‐triazine periphery

We have synthesized conjugated dendrimer with triazine peripheries, and their luminescence properties were investigated. The dendrimers consist of dendritic triazine wedges for electron transport, distyrylbenzene core as an emitting moiety, and t‐butyl peripheral groups for good processing properties. The dendrimers have LUMO values of about ?2.7 eV possibly because of the triazine moiety with high electron affinity. Photoluminescence study indicates that energy transfer occurs from the triazine wedges to the stilbene bridge, and finally to the core chromophore units due to a cascade decrease of bandgap from the peripheral wedge to core moiety. Therefore, the emission wavelength was determined by the structure of the core unit. The energy transfer efficiency of distyrylbenzene‐cored dendrimers was about 75 and 55% for Trz‐1GD‐DSB and Trz‐2GD‐DSB, respectively. A preliminary electroluminescence property also was investigated. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 254–263, 2006     

Comparative theoretical synthesis of high‐energy density materials 2,4,6‐trinitro‐1,3,5‐triazine

In this study, the optimal synthetic route for 2,4,6‐trinitro‐1,3,5‐triazine (TNTA) was investigated. The synthesis of TNTA was performed using cyanamide (H₂NCN) as a starting material. In the first stage, a radical addition reaction was used to generate melamine, which is the precursor of TNTA. In addition, a gaseous nitration reaction using nitrogen dioxide radicals (^?NO₂) as the nitration agent was used to gradually induce radical substitutions to convert dicyandiamide (H₂NCN)₂ to melamine (H₂NCN)₃. Additional nitration steps lead to triaminocyanide and, ultimately, TNTA. In addition, nitryl cyanide (O₂NCN) was also tested as a starting material for radical addition to generate dinitryl cyanide (O₂NCN)₂, trinitryl cyanide (O₂NCN)₃, and, finally, TNTA. The activation energy barrier in each of the reaction steps as well as the various synthetic routes were compared to provide insight into the design of more feasible routes for the synthesis of TNTA. © 2014 Wiley Periodicals, Inc.     

Facile Route to Novel Pyrazolo[3,4‐d]pyrimidine,Imidazo[1,2‐b] pyrazole,Pyrazolo[3,4‐d][1,2,3]triazine,Pyrazolo[1,5‐c][1,3,5]triazine and Pyrazolo[1,5‐c][1,3,5]thiadiazine Derivatives

A regioselective synthesis of novel pyrazolo[3,4‐d]pyrimidines, imidazo[1,2‐b]pyrazoles, pyrazolo[3,4‐d][1,2,3]triazine, pyrazolo[1,5‐c][1,3,5]triazine and pyrazolo[1,5‐c][1,3,5]thiadiazine incorporating a thiazole moiety was described via the reactions of the versatile, readily accessible 5‐amino‐3‐(phenylamino)‐N‐(4‐phenylthiazol‐2‐yl)‐1H‐pyrazole‐4‐carboxamide ( 1 ) with each of DMF‐DMA, phenylisothiocyanate, chloroacetyl chloride, phenacyl bromide, benzoylisothiocyanate and formalin, respectively. All structures of the newly synthesized compounds were elucidated by elemental analysis and spectral data.     

Hyperbranched‐upon‐dendritic macromolecules as unimolecular hosts for controlled release

Novel amphiphilic hyperbranched‐upon‐dendritic polymers with a dendritic polyester core, a linear poly(ε‐caprolactone) (PCL) inner shell, and a hyperbranched polyglycerol outer shell have been prepared. The structures of the hyperbranched‐upon‐dendritic polymers were characterized by using NMR spectra. The critical aggregating concentrations (CACs) of those amphiphilic hyperbranched‐upon‐dendritic polymers were measured by using pyrene as the polarity probe. To study the encapsulation performances of those hyperbranched‐upon‐dendritic polymers as unimolecular hosts, inter‐molecular encapsulation was carefully prevented by controlling the host concentrations below their CACs and by washing with good organic solvents. The study on encapsulation of two model guest molecules, pyrene and indomethacin, was performed. The amounts of encapsulated molecules were dependent mainly on the size of inner linear shells. About three pyrene molecules or five indomethacin molecules were encapsulated in hyperbranched‐upon‐dendritic polymers with average PCL repeating units of two but different hyperbranched polyglycerol outer shells, whereas about five pyrene molecules or about 12 indomethacin molecules were encapsulated in those with PCL repeating units of nine. The encapsulated molecules could be released in a controlled manner. Thus, the hyperbranched‐upon‐dendritic polymers could be used as unimolecular nanocarriers with controllable molecular encapsulation dosage for controlled release. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4013–4019, 2010     

Nitrogen‐rich Salts based on 3‐Dinitromethyl‐[1,2,4]triazine: Synthesis,Characterization, and Performance

1,1‐Diamino‐2,2‐dinitroethylene (FOX‐7), one of the most well‐known energetic materials, has attracted broad attention around the world. To extend the chemistry of FOX‐7, we present here a series of energetic salts based on 3‐dinitromethyl‐[1,2,4]triazine, which is prepared from FOX‐7. All these salts were fully characterized using ¹H NMR, ¹³C NMR, IR, and elemental analysis. In addition, the potassium salt ( 2 ), ammonium salt ( 5 ), and guanidinium salt ( 7 ) were further confirmed by single‐crystal X‐ray diffraction. Extensive hydrogen bonds were observed in these salts. The salts exhibit moderate densities varying from 1.63 to 1.76 g · cm^–3. All the compounds possess good thermal stability with decomposition temperatures from 118 to 267 °C. The detonation performance for salts were calculated by using EXPLO 5, their detonation velocities are in the range from 6807 to 8614 m · s^–1 and detonation pressures fall between 18.8 to 31.6 GPa. All the salts exhibit very low mechanical sensitivity, which indicates their potential application as insensitive energetic materials.     

具有生物活性的1,3,4-噻二唑并[3,2-a]-1,3,5-三嗪衍生物的合成方法

由1，3，4-噻二唑和1，3，5-三嗪稠合而成的1，3，4-噻二唑并[3，2．a]-1，3，5-三嗪衍生物具有广泛的生物活性，是一类重要的药用物质。本文对其在近二十年的合成方法进行了综述，重点介绍通过1，3，4-噻二唑衍生物为母体的合成方法。参考文献45篇。     

Density functional theory study of high‐pressure effect on crystalline 4,4′,6,6′‐tetra(azido)hydrazo‐1,3,5‐triazine

Periodic density functional theory calculations are performed to study the hydrostatic compression effects on the structure, electronic, and thermodynamic properties of the energetic polyazide 4,4′,6,6′‐tetra(azido)hydrazo‐1,3,5‐triazine (TAHT) in the range of 0?100 GPa. At the ambient pressure, the local density approximation/Ceperley‐Alder exchange‐correlation potential parameterized by Perdew and Zunger relaxed crystal structure compares well with the experimental results. The predicted heat of sublimation is 38.68 kcal/mol, and the evaluated condensed phase of formation (414.04 kcal/mol) approximates to the experimental value. The detonation velocity and detonation pressure for the solid TAHT are calculated to be 7.44 km/s and 23.71 GPa, respectively. When the pressure is exerted less than 35 GPa, the crystal structure and geometric parameters change slightly. However, at 36 GPa, the molecular structure, band structure, and density of states change abnormally because of the azide‐tetrazole transformation that has not been observed in gas phase or polar solvents. The azido group cyclizes to form a five‐membered tetrazole ring that is coplanar with the riazine ring and contributes to a larger conjunction system. As the pressure augments further to 80 GPa, the hydrogen transfer is found and a new covalent bond H2? N9 is formed. In the studied pressure range, the band gap decreases generally except for some breaks due to the molecular transformation and drops to nearly zero at 100 GPa, which means the electronic character of the crystal changes toward a metallic system. An analysis of the electronic structure shows that an applied pressure increases the impact sensitivity of TAHT. © 2012 Wiley Periodicals, Inc.     

New π‐conjugated polyaryleneethynylenes containing a 1,3,5‐triazine unit in the main chain: Synthesis and optical and electrochemical properties

A series of new π‐conjugated poly(aryleneethynylene)s containing a 1,3,5‐triazine unit in the main chain were synthesized in yields higher than 70% by polycondensation between dibromophenyl‐1,3,5‐triazine monomers and alkyl‐substituted diethynylbenzene (or diethynylfluorene) comonomers with Pd(PPh₃)₄ and CuI as catalysts in the presence of triethylamine. The polymers had a number‐average molecular weight in the range of 5000–10,000 and showed good solubility in common organic solvents. The polymers were photoluminescent both in solutions and in the solid state. X‐ray diffraction patterns of the powders of the polymers revealed that the polymers were semicrystalline. Electrochemically, the polymers appeared to be reversible under reduction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3797–3806, 2006     

Synthesis,characterization, and application of melamine‐based dendrimers supported on silica gel

Dendrimers based on melamine have been covalently attached to silica gel with convergent and divergent approaches. These approaches yield different products. Each step of the synthesis can be monitored with Fourier transform infrared spectroscopy, thermal gravimetric analysis, and X‐ray photoelectron spectroscopy. The organic molecules can be isolated by chemical etching the organosilica material with HF and then analyzed by mass spectrometry. The convergent approach, which relies on the solution‐phase synthesis of the dendrimer before its attachment onto silica gel, produces materials that are ～20% w/w organic regardless of the generation of the dendrimer used in the preparation of these composites and without apparent defects in the dendrimer structure. Materials prepared with the divergent approach show increasing percentages of organic material with each generation, but the dendrimers show structural defects including incomplete branching. In a survey of sequestration potential, materials obtained with the divergent approach removed more atrazine from solution than the more homogeneous materials obtained from the convergent approach. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 168–177, 2005     

Synthesis of Pyrazolo[1,5‐a][1,3,5]triazine,Pyrazolo[1,5‐a]pyrimidine,and Imidazo[1,2‐b]pyrazole Derivatives Based on Imidazo[2,1‐b]thiazole Moiety

3(5)‐Aminopyrazole derivative ( 6 ) has been synthesized by the reactions of the versatile unreported 2‐cyano‐N ′‐(1‐(3‐methyl‐6‐phenylimidazo[2,1‐b ]thiazol‐2‐yl)ethylidene)acetohydrazide ( 3 ) with phenyl isothiocyanate in KOH/DMF solution followed by reaction with methyl iodide and hydrazine hydrate. Reaction of compound 6 with some 1,3‐dicarbonyl compounds yielded pyrazolo[1,5‐a ]pyrimidine derivatives ( 14 – 17 ). Alkylation of compound 6 with various halo reagents, followed by intramolecular cyclization, yielded the corresponding imidazo[1,2‐b ]pyrazole derivatives 27 , 29 , 31 , and 33 . All newly synthesized compounds were elucidated by considering the data of both elemental analysis and spectral data.     

Synthesis of Certain 3-Aminopyrazolo[5,4-b]pyridine and 3,4-Substituted Pyrido[2′,3′：3,4]pyrazolo[5,1-c][1,2,4]triazine Derivatives

2-Thioxo-1,2-dihydropyridine derivatives 2a, 2b were reacted with methyl iodide to give 2-methylthiopyridines 3a, 3b, which were reacted with hydrazine hydrate to produce 3-aminopyrazolo[5,4-b]pyridines 4a, 4b. Compounds 4a, 4b were diazotized to afford the corresponding diazonium salts 5a, 5b, which were reacted with some active methylene compounds 6a-6h to give the corresponding pyrido[2′,3′ ： 3,4]pyrazole[5,1-c][1,2,4]triazines 7-14.