Nitrogen-rich Heterocycles Research Articles

Group 4 complexes supported by nitrogen-rich heterocycles bearing chalcogen donor atoms

Equimolar and excess ratio reactions of ligands [H{4,5-(P(E)Ph2)2tz}] [tz=1,2,3-triazole; E=S (1), Se (2)] with Ti(NR2)4 (R=Me, Et) yielded the disubstituted complexes [Ti(NR2)2{κ2-N,E-(4,5-(P(E)Ph2)2tz}2] [E=S, R=Me (3), Et (4); E=Se, R=Me (5), Et (6)], while the reactions of 1 and 2 with Ti(NEt2)2Cl2 gave the monosubstituted complexes [Ti(NEt2)Cl2{κ2-N,E-(4,5-(P(E)Ph2)2tz}] [E=S (7), Se (8)]. The reaction of M(NR2)4 (M=Zr, Hf, R=Me, Et) with 1 and 2 failed. However, the zirconium and hafnium disubstituted complexes, [M(NR2)2{κ2-N,E-(4,5-(P(E)Ph2)2tz}2] [M=Zr, E=S, R=Me (11), Et (12); M=Hf, E=S, R=Me (13), Et (14); M=Zr, E=Se, R=Et (15); M=Hf, E=Se, R=Et (16)] were obtained from the silylated derivatives [SiMe3{κ1-N-(4,5-(P(E)Ph2)2tz}] [E=S(9), Se(10)] and the corresponding metal amides M(NR2)4. In addition, the facile hydrolysis of 5, 7 and 8 with trace amounts of water led to the isolation of compounds 17–19, which contain Ti–O–Ti frameworks.

Ni-Catalyzed C–H Functionalization in the Formation of a Complex Heterocycle: Synthesis of the Potent JAK2 Inhibitor BMS-911543

BMS-911543 is a complex pyrrolopyridine investigated as a potential treatment for myeloproliferative disorders. The development of a short and efficient synthesis of this molecule is described. During the course of our studies, a Ni-mediated C-N bond formation was invented, which enabled the rapid construction of the highly substituted 2-aminopyridine core. The synthesis of this complex, nitrogen-rich heterocycle was accomplished in only eight steps starting from readily available materials.

Silver(i)-based energetic coordination polymers: synthesis, structure and energy performance

Two energetic compounds were reported to illustrate the substituent effect of nitrogen-rich heterocycles on the energy performance of energetic materials.

Synthesis of highly functionalized polycyclic quinoxaline derivatives using visible-light photoredox catalysis.

A mild and facile method for preparing highly functionalized pyrrolo[1,2-a]quinoxalines and other nitrogen-rich heterocycles, each containing a quinoxaline core or an analogue thereof, has been developed. The novel method features a visible-light-induced decarboxylative radical coupling of ortho-substituted arylisocyanides and radicals generated from phenyliodine(III) dicarboxylate reagents and exhibits excellent functional group compatibility. A wide range of quinoxaline heterocycles have been prepared. Finally, a telescoped preparation of these polycyclic compounds by integration of the in-line isocyanide formation and photochemical cyclization has been established in a three-step continuous-flow system.

Suzuki-Miyaura Cross-Coupling of Unprotected, Nitrogen-Rich Heterocycles: Substrate Scope and Mechanistic Investigation

The Suzuki-Miyaura cross-coupling of unprotected, nitrogen-rich heterocycles using precatalysts P1 or P2 is reported. The procedure allows for the reaction of variously substituted indazole, benzimidazole, pyrazole, indole, oxindole, and azaindole halides under mild conditions in good to excellent yields. Additionally, the mechanism behind the inhibitory effect of unprotected azoles on Pd-catalyzed cross-coupling reactions is described based on evidence gained through experimental, crystallographic, and theoretical investigations.

Molecular design of trinitromethyl-substituted nitrogen-rich heterocycle derivatives with good oxygen balance as high-energy density compounds

Density functional theory method was used to study the heats of formation (HOFs), electronic structure, energetic properties, and pyrolysis mechanism of a series of trinitromethyl-substituted heterocycle (including triazole, tetrazole, furazan, tetrazine, and fused heterocycles) derivatives. It is found that the fused ring, tetrazine, and tetrazole are effective structural units for increasing the HOFs of the derivatives. The substitution of the combination of nitro and trinitromethyl is very useful for improving their HOFs. The calculated energetic properties indicate that the combination of the nitro and trinitromethyl is very helpful for improving their detonation properties and oxygen balances (OB). Most of the title compounds have a good OB over zero. The OB of six compounds are very high and over 22. An analysis of the bond dissociation energies for several relatively weak bonds suggests that the N–O bond in the ring is a trigger bond for BIII-1, CI-3, and CI-4, and the ring–NO2 and (NO2)2C–NO2 bond cleavage is likely to happen in thermal decomposition for the remaining compounds. Considering the detonation performance and thermal stability, seven compounds could be regarded as potential candidates for high-energy compounds. Four compounds may be used as the novel high-energy oxidizers.

An unusually water-poor 5,5′-azobistetrazolate of dysprosium: stabilization of a nitrogen-rich heterocycle by a minimum of hydrogen bonds

In inorganic 5,5′-azobistetrazolate (C2N102−; ZT) compounds, the energetic ZT moiety is usually stabilized by H-bonds to lattice H2O and/or coordination of an N-atom of the tetrazole ring to the metal ion. Here we present the synthesis and characterization of a novel, salt-like compound, [Dy(H2O)8]2ZT3, which constitutes a unique exception to the above rule. We used supercritical CO2 as an unconventional desiccant in a straightforward metathesis reaction without abstaining from the benefits aqueous chemistry offers. It caused the crystallization of the title compound with a complex system of H-bonds between [Dy(H2O)8]3+ and ZT2− that involves almost every N-atom of the ZT2− anions as H-bond acceptors, which sufficiently stabilizes the energetic ZT despite the lack of lattice H2O or a coordinative bond to the metal ion.

Ultrafast Shock Compression and Shock-Induced Decomposition of 1,3,5-Triamino-2,4,6-trinitrobenzene Subjected to a Subnanosecond-Duration Shock: An Analysis of Decomposition Products

Shock compression studies of pressed and confined ultrafine 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) powder were conducted using ultrashort ~300 ps, ~50 GPa shock waves. The recovered decomposition products were characterized using X-ray photoelectron spectroscopy, infrared spectroscopy, and Raman spectroscopy. A substantial amount of shock-related chemistry was observed. Approximately 75% of the nitrogen atoms were liberated as gas-phase species, along with ~33% of the oxygen atoms, as a result of the applied shock. Furthermore, we observe C 1s binding energies suggesting the formation of sp(3) hybridized amorphous carbon. For comparison, a carbon nitride material was also prepared and characterized by thermally pyrolizing TATB. The shock-compressed TATB and the thermally pyrolized TATB are qualitatively different, suggesting that, carbon nitrides, a possible indicator of nitrogen-rich heterocycles precursors, are not a major product class for strongly overdriven shock conditions. These experimental conditions were, however, not detonation conditions, and the possible formation of nitrogen-rich heterocycles in actual detonations still exists.

Synthesis and properties of bis(pyrazino[2′,3′:4,5]imidazole)-fused 1,2,5,6-tetrahydro-1,4,5,8,9,10-hexaazaanthracenes: a new fluorescent nitrogen-rich heterocycle

Nitrogen-rich heterocycles, bis(pyrazino[2′,3′:4,5]imidazole)-fused 1,2,5,6-tetrahydro-1,4,5,8,9,10-hexaazaanthracenes (BPI-HAAs) were prepared by conventional Pd(OAc)2/BINAP-catalyzed C–N coupling reactions of 5-aryl-3-bromoaminopyrazines. The BPI-HAA core is a planar structure with aromaticity, and this heterocycle exhibits red fluorescence and moderate electron-accepting characteristics.

Nitrogen-Rich Heterocycles as Reactivity Retardants in Shocked Insensitive Explosives

We report the first quantum-based multiscale simulations to study the reactivity of shocked perfect crystals of the insensitive energetic material triaminotrinitrobenzene (TATB). Tracking chemical transformations of TATB experiencing overdriven shock speeds of 9 km/s for up to 0.43 ns and 10 km/s for up to 0.2 ns reveal high concentrations of nitrogen-rich heterocyclic clusters. Further reactivity of TATB toward the final decomposition products of fluid N(2) and solid carbon is inhibited due to the formation of these heterocycles. Our results thus suggest a new mechanism for carbon-rich explosive materials that precedes the slow diffusion-limited process of forming the bulk solid from carbon clusters and provide fundamental insight at the atomistic level into the long reaction zone of shocked TATB.

Structural Variety of Alkali Metal Compounds Containing P−E−M (E = S, Se; M = Li, Na, K) Units Derived from Nitrogen Rich Heterocycles

The preparation of novel alkali metal chalcogenides supported by multidentate nitrogen rich ligands is reported. Treatment of the ligand precursors [H{(4,5-(P(E)Ph(2))(2)tz}] (E = S (1a), Se (1b)) with organolithium reagents or elemental sodium and potassium in tetrahydrofuran (THF) leads to the isolation of 2-7 in high yields. These compounds were characterized by elemental analysis, IR spectroscopy, mass spectrometry, solution and solid-state multinuclear NMR spectroscopy, and single crystal X-ray diffraction analysis. In the solid state, 2, 4, and 5 are dimers that contain bimetallic six-membered (M(2)N(4)) rings (M = Li, Na). In 3, the discrete monomer [Li{4,5-(P(Se)Ph(2))(2)tz}(thf)(2)] (tz = 1,2,3-triazole) contains a five-membered CPSeLiN ring which adopts an envelope conformation. The polymeric arrangement [K{4,5-(P(S)Ph(2))(2)}tz](infinity) in 6 displays different bonding modes based on the hapticity of the ligand upon binding to the potassium atom. In compounds 2-6, the presence of secondary bonding features the alkali metal chalcogen bonds.

Strategies for Total and Diversity‐Oriented Synthesis of Natural Product(‐like) Macrocycles

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