Pd-Catalyzed Regioselective Arylation on the C‑5 Position of <i>N</i>‑Aryl 1,2,3-Triazoles

We herein report a highly efficient method for the arylation at the C-5 position of <i>N</i>-aryl 1,2,3-triazoles via a direct palladium catalyzed arylation reaction. The optimal reaction conditions required a combination of Pd­(OAc)₂ and tris­(<i>o</i>-tolyl)­phosphine as catalyst, and Cs₂CO₃ as the base under inert atmosphere. A variety of C-5 substituted <i>N</i>-aryl 1,2,3-triazoles were prepared using these conditions with yields in the 70–88% range. Regioselective C-5 arylations were also performed on 1,4-disubstituted 1,2,3-triazoles. The regioselectivity in triazole substitution at the C-5 position was confirmed by single crystal XRD. In addition, computational investigations of key steps of the catalytic cycle using the density functional theory have provided a rationalization to the selective C-5 arylation of <i>N</i>-aryl 1,2,3-triazoles

Studies on CL-20/HMX (2:1) Cocrystal: A New Preparation Method and Structural and Thermokinetic Analysis

A new preparation method for CL-20/HMX (2:1) cocrystal has been established at the laboratory level that is amenable for scale up. Solvent evaporation from a saturated solution of the stoichiometric mixture in the presence of a high boiling antisolvent, comparatively a very efficient and cheaper method, yielded pure cocrystals. Cocrystals were well characterized by spectroscopic, thermoanalytical tools, X-ray diffraction, and microscopic techniques. A correlation of percentage of cocrystal formation with evaporation rate has been obtained through quantitative analysis using Raman spectrometry. An evaporation rate of <1 mL/min consistently produced pure cocrystal confirmed by Raman and powder X-ray diffraction analysis. Thermokinetic analysis suggests the cocrystal to be more stable than CL-20 with an energy of activation of 65 kcal/mol, higher than CL-20 but inferior to HMX. Significant augmentation in the values of <i>k</i> and <i>A</i> over CL-20 justified a faster decomposition rate. Enhanced insensitivity toward friction and impact forces and higher measured velocity of detonation indicate improved performance on incorporation into high explosive formulations

Tailoring of energetic groups in acroyloyl polymers

<p>Acryloyl based novel energetic monomers having nitro acrylates and nitro triazole acrylates were synthesized and further used for polymerization. Due to scavanging properties of nitro groups, syntheses of nitro aromatic polymers are not facile at normal conditions. In this regard, we report a simple protocol to synthesize these energetic group embeded acroloyl polymers. These polymers were characterized by FTIR, and NMR spectroscopic techniques. gel permeation chromatography (GPC) technique was employed in order to understand molecular mass of these polymers along with average molecular weight, number average weight and poly dispersity index. Glass transition temperature (<i>T</i>_g) was determined by using DSC analysis. It was observed that with increase in nitro groups in polymers there is a decrease in glass transition temperature. Two steps degradation were depicted in the TGA thermograph in nitro containing polymers. Heat release during this reaction was found up to 951 J/g. Increase in nitrogen content in polymer unit enhanced the heat release of polymers.</p

Regiospecifically Fluorinated Polycyclic Aromatic Hydrocarbons via Julia–Kocienski Olefination and Oxidative Photocyclization. Effect of Fluorine Atom Substitution on Molecular Shape

A modular synthesis of regiospecifically fluorinated polycyclic aromatic hydrocarbons (PAHs) is described. 1,2-Diaryl­fluoroalkenes, synthesized via Julia–Kocienski olefination (70–99% yields), were converted to isomeric 5- and 6-fluorobenzo­[<i>c</i>]­phenanthrene, 5-and 6-fluorochrysene, and 9- and 10-benzo­[<i>g</i>]­chrysene (66–83% yields) by oxidative photocyclization. Photocyclization to 6-fluorochrysene proceeded more slowly than conversion of 1-styrylnaphthalene to chrysene. Higher fluoroalkene dilution led to a more rapid cyclization. Therefore, photocyclizations were performed at higher dilutions. To evaluate the effect of fluorine atom on molecular shapes, X-ray data for 5- and 6-fluorobenzo­[<i>c</i>]­phenanthrene, 6-fluorochrysene, 9- and 10-fluorobenzo­[<i>g</i>]­chrysene, and unfluorinated chrysene as well as benzo­[<i>g</i>]­chrysene were obtained and compared. The fluorine atom caused a small deviation from planarity in the chrysene series and decreased nonplanarity in the benzo­[<i>c</i>]­phenanthrene derivatives, but its influence was most pronounced in the benzo­[<i>g</i>]­chrysene series. A remarkable flattening of the molecule was observed in 9-fluorobenzo­[<i>g</i>]­chrysene, where the short 2.055 Å interatomic distance between bay-region F-9 and H-8, downfield shift of H-8, and a 26.1 Hz coupling between F-9 and C-8 indicate a possible F-9···H-8 hydrogen bond. In addition, in 9-fluorobenzo­[<i>g</i>]­chrysene, the stacking distance is short at 3.365 Å and there is an additional interaction between the C-11–H and C-10a of a nearby molecule that is almost perpendicular