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We describe the synthesis of a mesoion-derived nitroso compound, 5-nitroso-1,3-diphenyltetrazolium tetrafluoroborate ( 1 ), and its application in the oxidation of alcohols. The structure of 1 was fully characterized by X-ray analysis, showing that it exists as a monomer in the solid state. In the cyclic voltammetric analysis of 1 , a reversible redox peak was observed at 0.43 V (vs. Ag/Ag + in MeCN) under acidic conditions. It was subsequently shown that the nitrosotetrazolium salt 1 is capable of stoichiometrically oxidizing alcohols to the corresponding carbonyl compounds effectively. This nitroso heterocycle and its reduced form, i.e., the corresponding mesoionic hydroxyamide, participate in a redox cycle involving the catalytic oxidation of alcohols by the aid of HNO 3 under mild conditions. [ABSTRACT FROM AUTHOR]

A novel C–N cleavage strategy for the regioselective synthesis of 2-nitroso heterocyclic ketene aminals (HKAs) has been established. In this procedure, the C–N bond of nitrobenzenyl nitroethene is cleaved by the oxidation reaction and selective nitroso reaction of the α-carbon in HKAs. The presented synthetic route features excellent selectivity, straightforward purification and simple starting materials. [ABSTRACT FROM AUTHOR]

Abstract: Eight simple amides have been subjected to UV irradiation in the presence of either MNP or NO. In all cases radical species were generated: these were detected by means of EPR spectroscopy in the form of different nitroxides resulting from the trapping of the primary radicals. NO acted as a double spin trap, scavenging a radical to afford a diamagnetic nitroso derivative that in turn acted as trap towards another radical unit. As amido-groups are present in components of skin tissue and may be present in many therapeutic or cosmetic products used as skin sunscreen, and NO is a ubiquitous endogenous reactive species, the nitroxides detected in the present studies might participate in radical processes triggered by sun exposure and resulting in damages, even severe, of biological tissues. [Copyright &y& Elsevier]

Abstract: Although aminoxyl radicals are well-known as organic stable free radicals, the isomeric radicals, N-alkoxyaminyl radicals , are scarcely studied in the area of theoretical study. We carried out the theoretical calculation of the isotropic 14N hyperfine coupling constants (a N), g-factors, electronic absorbances, and generation mechanisms of N-alkoxyaminyl radicals. For thirty one N-alkoxyaminyl radicals, the PCM-DFT calculation at B3LYP/6-31+G(d,p) could well reproduce the experimental data of a N and g-factors, where R 2 were 0.9796 and 0.9439, respectively. The UV–vis spectra were moderately reproduced by PCM-TD-DFT (PBE0/6-31+G(d,p)), where R 2 was 0.9205. Additionally, the use of a linear scaling procedure precisely reproduced the UV–vis spectrum. The activation Gibbs free energies for the generation of N-alkoxyaminyl radicals and aminoxyl radicals in the competing reactions of nitroso compounds with alkyl radicals were estimated by DFT and coupled cluster calculations. The activation free energies for the generation of N-alkoxyaminyl radicals were estimated to be 9–18 kcal/mol at B3LYP/6-31+G(d,p). The reported product ratios in the competing reactions could be reasonably explained by the differences in the activation free energies. [Copyright &y& Elsevier]

Abstract: This article reports a simple and efficient synthesis of C-nitroso compounds (azodioxy esters or ketones and oximes) through a double oxidation of cyclic imines (4,5-dihydrooxazoles and 3,4-dihydro-2H-pyrroles) with m-CPBA. C-Nitroso derivatives seem to be potential donors of nitric oxide, one of the most powerful biological messenger. [Copyright &y& Elsevier]

Abstract: Magtrieve™ (CrO2) and MnO2 mediated oxidation of aldoximes to nitrile oxides were studied in details. In presence of external radical source, TEMPO, these reagents did not furnish nitrile oxides, instead favoured deoximation to aldehydes. A common trend of deoximation was established from electronically tuned aldoximes, which is: aliphatic>aromatic>aldoximes with strong electron-withdrawing group, though the extent of deoximation was less in case of CrO2. Above effects were not observed with chloramine-T and diacetoxyiodobenzene, reagents known to produce nitrile oxides via hydroximoyl halide or equivalent ionic intermediates. A putative reaction mechanism is proposed for MO2 (M=Cr, Mn) mediated oxidation of aldoximes through formation of a nitroso-oxime tautomeric pair. Formation of nitrile oxide is possibly occurred from the oxime tautomer via a σ-type iminoxy radical intermediate. The deoximation process, dominating in presence of external radical environment, is explained following decomposition of the nitroso tautomer. [ABSTRACT FROM AUTHOR]

Abstract: Tertiary aliphatic β- and γ-nitro nitriles and ketones deuterated in (several) selected positions had been synthesized. The deuterated nitro compounds served as a starting material for the corresponding deuterium labeled nitrones or hydroxylamines (reducing with aluminum amalgam). Further oxidation of the last two groups of compounds with sodium periodate or m-CPBA afforded the relevant deuterated tertiary C-nitroso compounds. [Copyright &y& Elsevier]

Abstract: α-Acyloxynitroso derivatives are a class of heterodienophiles leading to valuable 3,6-dihydro-1,2-oxazines or the corresponding aminoalcohols in good yields. The discovery that a β-oxygenated moiety led to a domino [4+2] cycloaddition/σN–O bond cleavage in the presence of a catalytic amount of Lewis acid was investigated in detail, through kinetic profiling of the reaction both in the absence and presence of a promoter. These studies showed that the role of the Lewis acid was to accelerate the σN–O bond cleavage thereby promoting a highly reproducible sequence. In addition, our preliminary results on an asymmetric version of this domino sequence are reported. [Copyright &y& Elsevier]

Abstract: 3-Arylindoles are produced in moderate to excellent yields from the reaction between aryl hydroxylamines and alkynes catalyzed by 10mol% iron(II) phthalocyanine [Fe(Pc)]. Terminal and internal alkynes afford 3-aryl substituted indoles exclusively. Electron-donating and -withdrawing groups are tolerated on the aryl hydroxylamine. A few bioactive indoles are synthesized as well as several new indoles using this one-step intermolecular annulation procedure. [Copyright &y& Elsevier]

Abstract: 2,4,6-Trinitrotoluene readily reacts with 1-nitroso-2-naphthol to afford 9,11-dinitrobenzo[f]naphtho[2,1-b][1,4]oxazepine. The nitro groups of the latter undergo displacement by O- and S-nucleophiles with preferential substitution of the 11-NO2 (peri-nitro group). The structures of the substitution products are confirmed by X-ray diffraction and 1H NMR NOE experiments. [Copyright &y& Elsevier]

Abstract: A novel SiO2–NHC–Cu(I) 3b was developed and used as a highly efficient catalyst for [3+2] cycloaddition of organic azides and terminal alkynes. In the presence of SiO2–NHC–Cu(I) 3b (1mol %), the reactions of terminal alkynes with organic azides underwent smoothly to generate the corresponding regiospecific 1,4-disubstituted 1,2,3-triazoles in excellent yields under solvent-free reaction conditions at room temperature. Furthermore, catalyst 3b was quantitatively recovered from the reaction mixture by a simple filtration and reused for 10 cycles without loss of its activity. [Copyright &y& Elsevier]

Abstract: The reactions of [60] fullerene with excess fluoroalkanesulfonyl azides RfSO2N3 in o-dichlorobenzene under thermal or microwave irradiation condition afforded monoadduct opened [5,6]-bridged azafulleroids. While, similarly treatment of 2,2,2-trifluoroethyl azides CF3CH2N3 with C60 gave two monoadducts, i.e., opened [5,6]-bridged azafulleroids, closed [6,6]-bridged Aziridino-fullerene, and some multi-addition product. A general mechanism for these addition reactions was proposed. [Copyright &y& Elsevier]

Abstract: Aromatic nitroso compounds in the presence of base and 2-(α-hydroxyalkyl)-3,4-dimethylthiazolium trifluoromethanesulfonate and related salts furnish in variable yields O- and N-acyl-aryl hydroxylamines and 3,4-dimethylthiazolium trifluoromethanesulfonate. A primary kinetic isotope effect of 4.9, obtained for the appropriate 2α-deuterated thiazolium salt, points to the C2α–H bond cleavage as the rate determining step. Radical species detected by ESR were unambiguously identified as phenylhydronitroxide, but attempted trapping of the corresponding C–heterocyclic radicals by TEMPO was not successful, and substrates incorporating a potential cyclopropyl radical clock gave products with the cyclopropyl ring intact. Theoretical calculations revealed a large activation energy for such reaction, which thus cannot per se exclude the intervention of such radical species. Evidence for the likely operation of two concurrent mechanisms, a radical and a preponderant ionic pathway, involving the conjugate base of the thiazolium salt, as the chemical model for ‘active thiamine’, and ArNO is presented for the formation of the products of the reaction. [Copyright &y& Elsevier]

Abstract: The nitroso group transfer from N-nitrososulfonamides to thiolate ions was studied. Based on the results, the reaction rate is strongly dependent on the nature of the leaving group , but virtually independent of the basicity of the thiol . This dependence is ascribed to the presence of a nucleophile desolvation equilibrium that is followed by the attack of the thiolate ion on the nitroso group via a concerted mechanism. The equilibrium constants for the loss of a nitroso group from a nitrosothiol and an N-nitrososulfonamide were used to obtain the equilibrium constants for the different reactions involved. By using rate–equilibrium correlations, the parameters , , and were obtained. [Copyright &y& Elsevier]

Abstract: 4-Hydroxy-l-proline, an amino acid, an important component of collagen, was transformed into its N-nitroso-derivative, (4R)-4-hydroxy-1-nitroso-l-proline, 1 by butylnitrite in the acidic medium. The structure is a cyclic hydroxy-N-nitrosoacid with the carboxyl and hydroxyl groups trans to each other. The carboxyl group is in the syn-conformation. In the structure, the neutral molecules are connected via classical intermolecular O–H⋯O hydrogen bonds involving the hydroxyl and carboxyl groups [O⋯O=2.6251(14)Å], and form chains along the a-axis direction. The chains are linked into sheets via O–H⋯O hydrogen bond, [O⋯O=2.6813(15)Å] with participation of oxygen atom of nitroso group. Ab initio calculations based on density functional theory at the B3LYP/6-311++G(d, p) level of theory were performed to analyze the influence of 4-hydroxy-l-proline (Hyp) nitrosation on the conformation of the synthesized N-nitroso-compound. The geometry optimization of 1 and initial 4-hydroxy-l-proline was carried out in the gas phase and in solution using the polarizable continuum model. The single-point calculation was performed for the crystal structure of 1. The most stable conformer of 1 is observed in an aqueous solution. In this state, the pyrrolidine ring adopts an envelope conformation, which is also maintained in the gas phase. The twisted conformation of the pyrrolidine ring is present in all states of Hyp and in the crystal structure of 1. In 1 the interchange of five-membered ring conformation in solution and in the gas phase in comparison with the crystal is accompanied by an increase of the dipole moment of the molecule, which is maximal in solution. [Copyright &y& Elsevier]

Abstract: The hydrochlorothiazide, 6-chloro-3,4-dihydro-2H-1,2,4-benzothiadiazine-7-sulfonamide-1,1-dioxide, ( HCTZ ), widely used as a diuretic and anti-hypertensive drug, was transformed into its N-nitroso-derivative, 6-chloro-4-nitroso-3,4-dihydro-2H-1,2,4-benzothiadiazine-7-sulfonamide-1,1-dioxide ( O N–HCTZ ) by sodium nitrite in an acidic medium. The crystalline complexes of O N–HCTZ with 18-crown-6 (18C6) and cis-anti-cis-dicyclohexyl-18C6 (DCH6B) demonstrated different H-bonding modes from those present in the co-crystals of HCTZ with the same crown ethers. The influence of the nitroso-group on the binding mode and crystal packing is discussed. [Copyright &y& Elsevier]