A New Approach to Ethyl 1-Aroyl/Aroylmethyl-5-methyl-3-methylthiopyrazole-4-carboxylates： High Regioselectivity in Alkylation and Acylation Reactions between N-1 and N-2 of a Pyrazole Derivative

It has been known that pyrazole ring has two main tautomeric isomers1-3as showed in Scheme1.The proton could migrate at the two nitrogen atoms of the pyrazole ring.Taylor E.C.and Purdum W.R.4first reported the synthesis of2as an isomer of2a.And so far,only a few literatures5-6have reported that this pyrazole derivative was in form2a,rather than2,therefore both acylation or alkylation reaction occurred at N-1of2a.But the regiochemistry of the N-substituted product of pyrazole has not been u…     

Poly(9‐undecyl‐9‐methyl‐fluorene) and poly(9‐pentadecyl‐9‐methyl‐fluorene): Synthesis,solution structure,and effect of side chain asymmetry on aggregation behavior

We report on solution aggregates and backbone conformation of poly(9‐undecyl‐9‐methyl‐fluorene) (PF1‐11) and poly(9‐pentadecyl‐9‐methyl‐fluorene) (PF1‐15), having two different side chains compared with poly(9,9‐dihexylfluorene) (PF6) and poly(9,9‐dioctylfluorene) (PF8) with two identical side chains. In the poor solvent methylcyclohexane (MCH), X‐ray scattering indicates that PF1‐11 and PF1‐15 appear as three‐dimensional aggregates (5–10 nm wide and thick), forming ribbon‐like agglomerates (correlation lengths of 100 nm). PF6 and PF8 appear as two‐dimensional aggregates (>10 nm wide and 2–3 nm thick) involving ribbon‐like agglomerates (correlation lengths much greater than 100 nm). Upon heating, all aggregates undergo a gel–sol transition which occurs at lower temperatures for PF1‐11 and PF1‐15 (<60°C) than for PF6 and PF8 (>80°C). In the good solvent toluene, PF1‐11 and PF1‐15 form networks of cylindrical particles. The mesh size and the cylinder radius are smaller in 24°C toluene (60 nm, 0.5 nm) than in 60°C MCH (300 nm, 1–2 nm). Nuclear magnetic resonance spectra in toluene‐d₈ together with density functional theory calculations suggest higher torsion angles between polymer repeat units for PF6, PF8, and PF1‐11 (less planar conformation) and a gauche arrangement of the dihedral angles between the bridge carbon atom and the side chain methylene groups in PF1‐15. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 826–837     

The Structure of Bis[N‐6‐aminopyridyl‐N‐(1S)‐(+)‐10‐camphorsulfonylamino]palladium in the Solid State and in Solution

The complex, bis[N‐6‐aminopyridyl‐N‐(1S)‐(+)‐10‐camphorsulfonylamino]palladium, Pd[(S)‐APCS]₂, 1 , was prepared by reaction of 2‐[(1S)‐(+)‐10‐camphorsulfonamino]‐6‐aminopyridine with PdCl₂ in THF. Complex 1 has been characterized by spectroscopic methods and its structure has been determined by X‐ray crystallography. Crystal data: space group C2, a= 16.082 (2), b = 17.104 (2), c = 13.051 (2)Å, β = 99.95 (1)°, V = 3535.9 (8) ų, Z = 2 with final residuals R1 = 0.0491 and wR2 = 0.0944. Two independent molecules, (S,S)‐Pd[(S)‐APCS]2, 1a , and (R,R)‐Pd[(S)‐APCS]2, 1b , were found in each asymmetric unit, which exchange to each other via a series of nitrogen inversion and C‐C bond rotation. The inversion energy (ΔGc₁^≠) and the energy barrier (δGc₂^≠) were 11.5 ± 0.1 Kcal mol^?1 at 246 K and 9.8 ± 0.1 Kcal mol^?1 at 199 K, respectively, calculated by dynamic NMR data.     

Fragmentation patterns of 4(5)‐nitroimidazole and 1‐methyl‐5‐nitroimidazole—The effect of the methylation

We present here the photofragmentation patterns of doubly ionized 4(5)‐nitroimidazole and 1‐methyl‐5‐nitroimidazole. The doubly ionized state was created by core ionizing the C 1s orbitals of the samples, rapidly followed by Auger decay. Due to the recent development of nitroimidazole‐based radiosensitizing drugs, core ionization was selected as it represents the very same processes taking place under the irradiation with medical X‐rays. In addition to the fragmentation patterns of the sample, we study the effects of methylation on the fragmentation patterns of nitroimidazoles. We found that methylation alters the fragmentation significantly, especially the charge distribution between the final fragments. The most characteristic feature of the methylation is that it effectively quenches the production of NO and NO⁺, widely regarded as key radicals in the chemistry of radiosensitization by the nitroimidazoles.     

Tandem Ring Opening and Oximation of Ethyl 3‐Aroyl‐1‐cyano‐4‐hydroxy‐2,4,6‐triarylcyclohexanecarboxylate by Hydroxylamine

The reaction of hydroxylamine hydrochloride with ethyl 3‐aroyl‐1‐cyano‐4‐hydroxy‐2,4,6‐triarylcyclohexanecarboxylate has led to the formation of ethyl 2‐[amino(hydroxyimino)methyl]‐3‐aryl‐5‐(hydroxyimino)‐5‐arylpentanoate via a tandem ring opening and oximation process. The structures of the products are confirmed by NMR and X‐ray techniques, and the conformational features of the product arrived at are compared with a molecular dynamics simulation study.     

4‐Bromo‐3‐methyl‐1‐phenylpyrazole in Heterocyclic Synthesis: Unexpected Polysubstituted Pyrazole Derivatives

Unexpected 4,4′‐dipyrazolomethylidene ( 7 ), 4‐amino‐3a‐bromo‐3‐methyl‐1‐phenylpyrazolo[3,4‐b]pyridin‐6‐thione ( 9 ), 4,4′‐dipyrazolyl ( 18 ), ethyl 4‐(3‐methyl‐1‐phenylpyrazole‐4‐yl)fuoro[2,3‐c]pyrazole‐4‐carboxylate ( 25 ), as well as the expected fuoro[2,3‐c]pyrazole derivatives ( 15 ), ( 20 ) and ( 28 ) were isolated from a one‐pot reaction of 4‐bromo‐3‐methyl‐1‐phenylpyrazole ( 1 ) with some readily available reagents.     

Experimental and quantum chemical calculational studies on N‐[4‐(3‐Methyl‐3‐phenyl‐cyclobutyl)‐thiazol‐2‐yl]‐N′‐pyridin‐3ylmethylene‐hydrazine

The title molecule, N‐[4‐(3‐Methyl‐3‐phenyl‐cyclobutyl)‐thiazol‐2‐yl]‐N′‐pyridin‐3ylmethylene‐ hydrazine (C₂₀ H₂₀ N₄ S₁), was characterized by ¹H‐NMR, ¹³C‐NMR, IR, UV‐visible, and X‐ray determination. In addition to the molecular geometry from X‐ray experiment, the molecular geometry, vibrational frequencies and gauge including atomic orbital ¹H‐ and ¹³C‐NMR chemical shift values of the title compound in the ground state have been calculated using the Hartree‐Fock and density functional method (B3LYP) with 6‐31G(d, p) basis set. The calculated results show that optimized geometries can well reproduce the crystal structural parameters. By using time‐dependent density functional theory method, electronic absorption spectrum of the title compound has been predicted. © 2011 Wiley Periodicals, Inc.     

Conformational Polymorphism in N‐(4′‐methoxyphenyl)‐ 3‐bromothiobenzamide

Three conformational polymorphs of N‐(4′‐methoxyphenyl)‐3‐bromothiobenzamide, yellow α, orange β, and yellow γ, have been identified by single‐crystal X‐ray diffraction. The properties and structure of the polymorphs were examined with FT Raman, FTIR (ATR), and UV/Vis spectroscopy, as well as differential scanning calorimetry. Computational data on rotational barriers in the isolated gas‐phase molecule indicate that the molecular conformation found in the α form is energetically preferred, but only by around 2 kJ mol^?1 over the γ conformation. The planar molecular structure found in the β form is destabilized by 10–14 kJ mol^?1, depending on the calculation method. However, experimental evidence suggests that the β polymorph is the most stable crystalline phase at room temperature. This is attributed to the relative planarity of this structure, which allows more and stronger intermolecular interactions, that is, more energetically effective packing. Calculated electronic‐absorption maxima were in agreement with experimental spectra.     

Reactions with 4‐Hydroxy‐2‐methylbutananilides: Unexpected Formation of a Cyclopropanecarboxamide

The successive treatment of the N,N‐disubstituted 4‐hydroxy‐2‐methylbutanamide 2a with lithium diisopropylamide (LDA) and diphenyl phosphorochloridate (DPPCl) led to the 1‐methylcyclopropanecarboxamide 10 in good yield. This base‐catalyzed cyclization offers a new approach to cyclopropanecarboxamides. Under similar conditions, the N‐monosubstituted 4‐hydroxy‐2‐methylbutanamide 2b gave the 3‐methylpyrrolidin‐2‐one 11 . The structure of the cyclopropanecarboxamide 10 was established by X‐ray crystallography.     

A novel 4‐methylene‐3‐borahomoadamantane: 1,1‐organoboration of an alkyn‐1‐ylsilane using 1‐boraadamantane

1,1‐Dibromo‐2,2‐bis(trimethylsilylethynyl)ethene ( 2 ) reacts with two equivalents of 1‐boraadamantane ( 1 ) by 1,1‐organoboration of both trimethylsilylethynyl groups to give a triene 3 bearing two 4‐methylene‐3‐borahomoadamantane moieties in terminal positions. The triene was characterized by one‐ and two‐dimensional ¹H, ¹¹B, ¹³C and ²⁹Si NMR spectroscopy in solution and X‐ray structural analysis in the solid state. The planes of the C double bond are strongly twisted against each other as a result of the bulky substituents, and the surroundings of the boron atoms deviate from the ideal trigonal planar geometry owing to the tension in the tricyclic frameworks. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis of (3,5‐Aryl/methyl‐1H‐Pyrazol‐1‐yl)‐(5‐Arylamino‐2H‐1,2,3‐Triazol‐4‐yl)Methanone

Some new (3,5‐aryl/methyl‐1H‐pyrazol‐1‐yl)‐(5‐arylamino‐2H‐1,2,3‐triazol‐4‐yl)methanones were synthesized and characterized by ¹HNMR, ¹³C NMR, MS, IR spectra data and elemental analyses or high resolution mass spectra (HRMS). During the procedure, Dimroth rearrangement was used in this synthesis.     

Novel Nucleophilic Substitution Reactions of 5‐Halo‐4‐Sulfur‐Substituted 5,6‐Dihydro‐2‐Pyridones

The title compounds ( 3 , 8 , 9 and 10 ) were efficiently synthesized, and their substitution reactions with various nucleophiles were carried out. The effects of leaving group, sulfur‐substituent, solvent, reaction temperature, and the nature of the nucleophiles on the reactivity and S_N2/S_N2′ regioselectivity were studied and rationalized with semi‐empirical calculations.     

1H and 13C NMR analysis of 2‐acetamido‐3‐mercapto‐3‐methyl‐N‐aryl‐butanamides and 2‐acetamido‐3‐methyl‐3‐nitrososulfanyl‐N‐aryl‐butanamide derivatives

The complete assignment of the ¹H and ¹³C NMR spectra of various 2‐acetamido‐3‐mercapto‐3‐methyl‐N‐aryl‐butanamides and 2‐acetamide‐3‐methyl‐3‐nitrososulfanyl‐N‐aryl‐butanamides with p‐methoxy, o‐chloro and m‐chloro substituents is reported. Copyright © 2013 John Wiley & Sons, Ltd.     

Experimental and theoretical investigation of the molecular and electronic structure of N′‐benzylidene‐N‐[4‐(3‐methyl‐3‐phenyl‐cyclobutyl)‐thiazol‐2‐yl]‐chloro‐acetic acid hydrazide

The title compound, N′‐benzylidene‐N‐[4‐(3‐methyl‐3‐phenyl‐cyclobutyl)‐thiazol‐2‐yl]‐chloro‐acetic acid hydrazide, has been synthesized and characterized by elemental analysis, IR, ¹H and ¹³C NMR, and X‐ray single crystal diffraction. The compound crystallizes in the orthorhombic space group P 21 21 21 with a = 5.8671 (3) Å, b = 17.7182 (9) Å, and c = 20.6373 (8) Å. Moreover, the molecular geometry from X‐ray experiment, the molecular geometry, vibrational frequencies, and gauge‐including atomic orbital ¹H and ¹³C chemical shift values of the title compound in the ground state have been calculated by using the Hartree–Fock and density functional methods (B3LYP) with 6‐31G(d) and 6‐31G(d,p) basis sets. The results of the optimized molecular structure are exhibited and compared with the experimental X‐ray diffraction. Besides, molecular electrostatic potential, Frontier molecular orbitals, and thermodynamic properties of the title compound were determined at B3LYP/6‐31G(d) levels of theory. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

The Structure of 2‐[(1S)‐(+)‐10‐camphorsulfonamino]‐6‐aminopyridine in the Solid State and in Solution; Unprecedented Cocrystallization of Four Stereoisomers

The solid and solution structures of a new optically active aminopyridine compound, 2‐[(1S)‐(+)‐10‐camphorsulfonamino]‐6‐aminopyridine [(S)‐csaap], 1 , are reported. Crystal data: space group P2₁, a = 8.9729 (5), b = 10.9447 (6), c = 36.693 (2) Å, β = 96.435 (1)°, V = 3580.8 (3) ų, Z = 8, R₁ = 0.0673 and wR₂ = 0.1600 with I > 2σ(I). This chiral compound shows an unprecedented cocrystallization of four stereoisomers, which are characterized by X‐ray crystallography and NMR spectroscopy.     

The Chemistry of 5‐(Tetrazol‐1‐yl)‐2H‐tetrazole: An Extensive Study of Structural and Energetic Properties

5‐(Tetrazol‐1‐yl)‐2H‐tetrazole ( 1 ), or 1,5′‐bistetrazole, was synthesized by the cyclization of 5‐amino‐1H‐tetrazole, sodium azide and triethyl orthoformate in glacial acetic acid. A derivative of 1 , 2‐methyl‐5‐(tetrazol‐1‐yl)tetrazole ( 2 ) can be obtained by this method starting from 5‐amino‐2‐methyl‐tetrazole. Furthermore, selected salts of 1 with nitrogen‐rich and metal (alkali and transition metal) cations, including hydroxylammonium ( 4 ), triaminoguanidinium ( 5 ), copper(I) ( 8 ) and silver ( 9 ), as well as copper(II) complexes of both 1 and 2 were prepared. An intensive characterization of the compounds is given, including vibrational (IR, Raman) and multinuclear NMR spectroscopy, mass spectrometry, DSC and single‐crystal X‐ray diffraction. Their sensitivities towards physical stimuli (impact, friction, electrostatic) were determined according to Bundesamt für Materialforschung (BAM) standard methods. Energetic performance (detonation velocity, pressure, etc.) parameters were calculated with the EXPLO5 program, based on predicted heats of formation derived from enthalpies computed at the CBS‐4M level of theory and utilizing the atomization energy method. From the analytical and calculated data, their potential as energetic materials in different applications was evaluated and discussed.     

Synthesis and molecular structures of 1‐boracyclopent‐2‐enes

The reaction of 1‐silyl‐1‐borylalkenes with alkyn‐1‐yltin compounds affords borol‐2‐enes, organometallic‐substituted allenes, mixtures thereof or even more complex mixtures with buta‐1,3‐dienes, depending on the third substituent at the C?C bond (Bu or Ph), on the number of Si? Cl functions (two or three) and the nature of the alkyn‐1‐yltin compound. Six new borol‐2‐enes were isolated in pure state, and two of them were characterized by X‐ray structural analysis. The solution‐state structures of all major products were clearly established by multinuclear magnetic resonance methods (¹H, ¹¹B, ¹³C, ²⁹Si, ¹¹⁹Sn NMR). Copyright © 2009 John Wiley & Sons, Ltd.     

Crystallographic report: Crystal structure of tetra(4‐methyl‐5‐imidazole‐carboxyaldehyde)zinc(II) diperchlorate

The central zinc(II) atom in the title complex is tetrahedrally coordinated by four nitrogen atoms derived from 4‐methyl‐5‐imidazolecarboxyaldehyde ligands with Zn? N in the range 2.007(3) to 2.026(4) Å. Copyright © 2003 John Wiley & Sons, Ltd.     

Synthesis and molecular structures of 1‐chloro‐1‐silacyclopent‐2‐enes. Combination of 1,2‐hydroboration, 1,1‐organoboration and protodeborylation

The reaction of alkyn‐1‐yl(chloro)(methyl)vinyl‐ and alkyn‐1‐yl(chloro)(phenyl)‐vinylsilane with 9‐borabicyclo[3.3.1]nonane (9‐BBN) afforded selectively 1‐silacyclopent‐2‐ene derivatives containing a Si? Cl function, as a result of consecutive 1,2‐hydroboration and 1,1‐organoboration. Protodeborylation with acetic acid left the Si? Cl functions in various 1‐silacyclopent‐2‐enes untouched, whereas acetic acid in the presence of dipropylamine led to conversion of the Si? Cl into the Si? OAc function. New starting materials and all products were characterized in solution by multinuclear NMR spectroscopy (¹H, ¹¹B, ¹³C and ²⁹Si NMR), and the molecular structures of two 1‐silacyclopent‐2‐ene derivatives were determined by X‐ray analysis. The gas phase geometries of 1‐silacyclopent‐2‐enes were optimized by DFT calculations [B3LYP/6‐311 + G(d,p) level of theory], found to be in reasonable agreement with the results of the crystal structure determination, and NMR parameters were calculated at the same level of theory. Copyright © 2009 John Wiley & Sons, Ltd.     

Energetic Materials Based on the 5‐Azido‐3‐nitro‐1, 2,4‐tri­azolate Anion

This study presents the preparation of 5‐azido‐3‐nitro‐1H‐1, 2,4‐triazole ( 1 ) in both good yield and high purity, starting from commercially available chemicals in a three step synthesis. Furthermore, several metal and nitrogen‐rich salts with sodium ( 3 ), potassium ( 4 ), cesium ( 5 ), silver ( 6 ), lead ( 7 ), ammonium ( 8 ), guanidinium ( 9 ), and aminoguanidinium ( 10 ) were prepared by simple acid‐base reactions. All compounds were well characterized by various means, including vibrational (IR, Raman) and multinuclear (¹H, ¹³C, ¹⁴N, ¹⁵N) NMR spectroscopy, mass spectrometry, and DSC. Additionally the structure of 7 was determined by single‐crystal X‐ray diffraction. The sensitivities towards various outer stimuli (impact, friction, electrostatic discharge) were determined according to BAM standards. The metal salts were tested as potential primary explosives utilizing various preliminary tests.