Two Energetic Framework Materials Based on DNM-TNBI as Host Molecule: Effectively Coordinated by Different Cations.

With the demand of develop outstanding-performance energetic materials, 1-(dinitromethyl)-4,4',5,5'-tetranitro-1H,1'H-2,2'-biimidazole (DNM-TNBI) emerged as a great contender (D: 9102 m ⋅ s-1; P: 37.6 GPa). However, the relatively poor thermal stability (Td: 142 °C) limits its practical application. In this study, DNM-TNBI as a host molecule to synthesize two new energetic open-framework materials by effectively coordinated with different cations. Their supramolecular structures were investigated and indicated that [DNM-TNBI2 -][2NH4 +] and [DNM-TNBI2 -][2K+] can be classified as a new energetic hydrogen-bonded ammonium framework (EHAF) and an energetic metal organic framework (EMOF). Meanwhile, their thermal stabilities are higher than that of DNM-TNBI and have satisfactory detonation performance ([DNM-TNBI2 -][2NH4 +], D: 8050 m ⋅ s-1, P: 26.4 GPa; [DNM-TNBI2 -][2K+], D: 8301 m ⋅ s-1, P: 30.8 GPa).

Challenging the Limitations of Tetranitro Biimidazole through Introducing a gem-Dinitromethyl Scaffold.

A gem-dinitromethyl group was successfully introduced into the TNBI·2H2O structure (TNBI: 4,4',5,5'-tetranitro-2,2'-bi-1H-imidazole) to obtain 1-(dinitromethyl)-4,4',5,5'-tetranitro-1H,1'H-2,2'-biimidazole (DNM-TNBI). Benefiting from the transformation of an N-H proton into a gem-dinitromethyl group, the current limitations of TNBI were well solved. More importantly, DNM-TNBI has high density (1.92 g·cm-3, 298 K), good oxygen balance (15.3%), and excellent detonation properties (Dv = 9102 m·s-1, P = 37.6 GPa), suggesting that it has great potential as an oxidizer or a high-performance energetic material.

TDDFT calculations of the PETN's ultraviolet absorption spectrum under the electric field loading.

CONTEXT: The UV(ultraviolet) absorption spectrum of PETN under different electric field loading directions(X, Y, and Z) with the value of strength range from 0.001 a.u. to 0.006 a.u. was calculated with the TDDFT(Time-dependent density functional) in this work. With the increase of electric field strength, the absorbance of PETN in the ultraviolet band decreases. To explain the action mechanism of the electric field on PETN UV(ultraviolet) absorption spectrum, we analyzed and counted the contribution rate, oscillator strength, and vertical excitation energy of the main excitation process whose contribution rate to the UV absorption spectrum is greater than 10%. The contribution of PETN to the UV spectrum in all directions without an electric field was also listed to investigate the anisotropy of PETN in the excitation process under an electric field. The hole-electron analysis showed that the electric field will enhance the charge transfer characteristics in the excitation process of PETN. To investigate the anisotropy of the response under different electric field application directions, the contribution of the UV absorption spectrum in different directions was studied. METHODS: Optimization and TDDFT calculation were performed at the level of M06-2X/def2-TZVP and PBE0/def2-TZVP respectively, with Gaussian09 program. The hole-electron analysis and UV absorption spectrum plotting were performed with Multiwfn3.8.

Collective Total Syntheses of Five Lycopodium Alkaloids.

It is reported herein that by exploiting the commonly shared bicyclic decahydroquinoline motif, a gold-catalyzed enamide-alkyne cycloisomerization reaction is developed to access tricyclic cores in a simple way. These tricyclic cores further serve as an advanced platform for the divergent enantioselective collective total syntheses of five Lycopodium alkaloids, belonging to three different structural types, in a concise and protecting-group-free fashion. The key transformations in the second phase include: 1) a transannular reductive Heck cyclization for installation of the azepane ring in fawcettidine, fawcettimine, and lycoposerramine Q; 2) a domino Mukaiyama hydration/Grob fragmentation process for construction of the ten-membered lactam system in phlegmariurine B; 3) a Fukuyama one-pot protocol for the construction of the 2-pyridone motif in lycoposerramine R. The newly developed strategy is expected to pave the way for the synthesis of other structurally related Lycopodium alkaloids.

Total Synthesis of Aspidofractinine Alkaloid Paucidirinine.

The first total synthesis of paucidirinine (1d), a highly congested aspidofractinine alkaloid containing a special contracted five-membered lactam ring, was achieved in 10 steps with 8% overall yield from commercially available materials. Several key maneuvers, including tandem enamination/[4 + 2] cycloaddition reaction and SmI2-promoted radical cyclization, were featured in this potentially scalable strategy.

A rapid construction of the ABC tricyclic skeleton of malabanone A.

The construction of the ABC tricyclic skeleton of malabanone A with the required 4 stereocenters was accomplished in a concise route starting from R-carvone. The synthesis featured an intramolecular [3 + 2] cycloaddition reaction to assemble its A ring and an intramolecular Diels-Alder reaction to construct its C ring.

Visible-light-mediated radical cascade reaction: synthesis of 3-bromocoumarins from alkynoates.

A visible-light-mediated radical addition of alkynoates to generate 3-bromocoumarins by using N-bromosuccinimide as the bromo source has been accomplished. This procedure provides a bromo radical addition/spirocyclization/ester migration cascade reaction under very mild reaction conditions without using any catalyst or strong oxidant and does not need high reaction temperature. Furthermore, the reaction can also be enlarged to the gram scale, and the product 3-bromocoumarins can be further applied in the synthesis of complex compounds.

(3 + 2)-Annulation of p-Quinamine and Aryne: A Strategy To Construct the Multisubstituted Hydrocarbazoles.

A strategy for the synthesis of multisubstituted hydrocarbazoles has been developed through (3 + 2)-annulation of p-quinamines and arynes. In this way, new analogs of hydrocarbazoles with quaternary carbon center can be synthesized in satisfactory yield under mild conditions. Furthermore, this (3 + 2)-annulation can be easily scaled-up, and the products can be modified through simple transformation.

Visible-light-mediated radical insertion/cyclization cascade reaction: synthesis of phenanthridines and isoquinolines from isocyanides.

A visible-light promoted single electron oxidation of ether enabled by photoredox catalysis has been accomplished. This procedure initiates a novel radical insertion/cyclization cascade reaction to generate phenanthridines and isoquinolines from easily available isocyanides under mild reaction conditions.

Visible-Light-Promoted Dual C-C Bond Formations of Alkynoates via a Domino Radical Addition/Cyclization Reaction: A Synthesis of Coumarins.

A visible-light-promoted, mild, and direct difunctionalization of alkynoates has been accomplished. This procedure provides a new strategy toward synthesis of the coumarin core structure by photoredox-mediated oxidation to generate the α-oxo radical, which supervenes a domino radical addition/cyclization reaction in moderate to good yields with high regioselectivity at ambient temperature.

An Efficient Synthesis of Benzazocines by Gold(I)-Catalyzed Tandem 1,2-Acyloxy Shift/[3+2] Cycloaddition of Terminal 1,9-Enynyl Esters.

An effective synthesis of structurally diverse benzazocines was accomplished in good to excellent chemical yields (55-82 %) through a gold(I)-catalyzed cascade reaction involving tandem 1,2-acyloxy shift/[3+2] cycloaddition of terminal 1,9-enynyl esters. The reaction proceeds under extremely mild conditions and represents one of the relatively few transition-metal-catalyzed intramolecular cycloaddition reactions for the synthesis of benzazocines.