V. A. Tartakovsky

Ionic Liquids as Unique Solvents in One‐Pot Synthesis of 4‐(N,2,2,2‐Tetranitroethylamino)‐3‐R‐Furazans

An efficient two-step one-pot protocol for the synthesis of N-nitrated trinitroethylamino furazans in an ionic liquid has been developed involving the condensation of aminofurazans with trinitroethanol and the N-nitration of an intermediate Mannich base. Trinitroethylnitramino derivatives have been synthesized and characterized by multinuclear NMR spectroscopy and X-ray crystallography. A role of the N,2,2,2-tetranitroethylamino group for stabilization of the high-density crystal-packing motif is described. The performance calculations gave detonation pressures and velocities for the furazan derivatives in a range of about 31-36 GPa and 8330-8745 ms(-1), respectively, which makes them competitive energetic materials. Furthermore, due to the positive oxygen balance, the compounds could be potential oxidizers for energetic formulations.

Synthesis of Tetrazino‐tetrazine 1,3,6,8‐Tetraoxide (TTTO)

This study presents the first synthesis and characterization of a new high energy compound [1,2,3,4]tetrazino[5,6-e][1,2,3,4]tetrazine 1,3,6,8-tetraoxide (TTTO). It was synthesized in ten steps from 2,2-bis(tert-butyl-NNO-azoxy)acetonitrile. The synthetic strategy was based on the sequential closure of two 1,2,3,4-tetrazine 1,3-dioxide rings by the generation of oxodiazonium ions and their intramolecular coupling with tert-butyl-NNO-azoxy groups. The TTTO structure was confirmed by single-crystal X-ray.

Benzo-1,2,3,4-tetrazine 1,3-Dioxides: Synthesis and NMR Study

Benzo-1,2,3,4-tetrazine 1,3-dioxides (BTDOs) represent fairly stable high-nitrogen systems, incorporating two head-to-tail linked azoxy groups. The synthetic pathway to these heterocycles suggested the use of the tert-butyl-NNO-azoxy group as a building block, allowing the first azoxy group to be incorporated into the ring. The second azoxy group was added with the help of the oxodiazonium ion (−N=N=O+) or its synthetic equivalent. This could be generated by two new methods. The first of these involved treatment of N-nitroamines with nitrating agents, and the second treatment of diazonium salts with peracids in the presence of a base. The proposed key stage in the tetrazine 1,3-bis(N-oxide) ring formation is the reaction between the oxodiazonium ion and the distal nitrogen atom of the tert-butyl-NNO-azoxy group, followed by elimination of the tert-butyl cation. The syntheses of bromo-BTDOs 3b−f and nitro-BTDOs 4a−c are described. The BTDOs were characterized by NMR, including 14N and 15N experiments. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Trifluoromethylation of N-Benzoylhydrazones

A method for the nucleophilic trifluoromethylation of N-benzoylhydrazones using Me3SiCF3/AcONa has been described. The CN bond of the hydrazones is activated by difluoroboron group, which is introduced by means of boron trifluoride and allylsilane.

On the structure and spectra of dinitramide salts

Abstract The preparation for the isotopically substituted dinitramide salts has been proposed. The 14 N and 15 N NMR spectra of the 15 N-enriched dinitramide anion in solution are measured and interpreted for the first time. New experimental IR and Raman spectra are obtained for the NH 4 + and K + salts of dinitramide in the solid state and in solution. The assignments are made with the help of quantum-mechanical force field calculations and normal-coordinate analysis. The harmonic vibrational spectrum of the dinitramide anion calculated at the B3LYP/6-31+G(d) level in the presence of solvent correlates best with the experimental data. The structure and spectra of the M + CH(NO 2 ) 2 − and M + N(NO 2 ) 2 − (M denotes a counterion) are compared and discussed. Topology of the electron charge density in the dinitramide anion is analyzed within the framework of Baders theory of atoms in molecules.

Fluorocyanation of enamines.

A method for the fluorocyanation of enamines has been described. The reaction involves fluorination of the electron rich double bond with N-F reagent (Selectfluor or NFSI) accompanied by trapping of beta-fluoroiminium cationic intermediate with cyanide nucleophile.

Chemistry of N,N-Bis(silyloxy)enamines, Part 5†

Aliphatic nitro compounds can be considered as good precursors of a wide variety of α-azolyl-substituted oximes. The double silylation of convenient aliphatic nitro compounds and the subsequent N,C-coupling of the resulting N,N-bis(silyloxy)enamines 3 with N-silylated azoles 4 lead to the formation of the silylated α-azolyl-substituted oximes 6, which can be smoothly desilylated to give the target α-azolyl-substituted oximes 5. The mechanism of the key step of this process – N,C-coupling – includes the generation of corresponding conjugated nitrosoalkenes 7 (Schemes 4 and 5). The contribution of the chain mechanism in the overall process is considered as well. The studies of the scope and limitations of this reaction, as well as the optimization of its conditions were accomplished. The configuration of the CN bond in oximes was established by NMR.

Synthesis of PDE IVb Inhibitors. 3. Synthesis of (+)-, (−)-, and (±)-7-[3-(Cyclopentyloxy)-4-methoxyphenyl]hexahydro-3H-pyrrolizin-3-one via Reductive Domino Transformations of 3-β-Carbomethoxyethyl-Substituted Six-Membered Cyclic Nitronates

Simple three-step asymmetric and racemic syntheses of GlaxoSmithKlines highly potent PDE IVb inhibitor 1 were developed. The suggested approach is based on reductive domino transformations of 3-β-carbomethoxyethyl-substituted six-membered cyclic nitronates, which are easily accessed by a stereoselective [4 + 2] cycloaddition of an appropriate nitroalkene to vinyl ethers. In vitro studies of PDE IVb inhibition by enantiomeric pyrrolizidinones (+)-1 and (-)-1 were performed.

Synthesis of PDE IVb Inhibitors. 1. Asymmetric Synthesis and Stereochemical Assignment of (+)- and (−)-7-[3-(Cyclopentyloxy)-4-methoxyphenyl]hexahydro-3H-pyrrolizin-3-one

Asymmetric synthesis of GlaxoSmithKlines highly potent phosphodiesterase inhibitor 1 has been accomplished in nine steps and 16% overall yield. The original strategy suggested involves as a key step the silylation of enantiopure six-membered cyclic nitronates 4 obtained by a highly stereoselective [4 + 2]-cycloaddition of an appropriate nitroalkene 5 to trans-1-phenyl-2-(vinyloxy)cyclohexane. Functionalization of the resulting 5,6-dihydro-4H-1,2-oxazine and subsequent stereoselective reduction of 1,2-oxazine ring in intermediate 2 furnished the pyrrolizidinone framework with the recovery of chiral auxiliary alcohol.

Synthesis of 1-alkyl-1,2,4-triazolium 4-nitroimides by alkylation of 4-nitramino-1,2,4-triazole salts

A method for the synthesis of 1-alkyl-1,2,4-triazolium 4-nitroimides was developed based on alkylation of 4-nitramino-1,2,4-triazole Na and Ag salts with halo- and dihaloalkanes.