Conformational analysis of 5-bromo-5-nitro-1,3-dioxane

Conformational analysis of 5-bromo-5-nitro-1,3-dioxane has been performed by computer simulation in terms of HF/pVDZ, hybrid DFT PBE/3ξ, and RI-MP2/λ2 quantum chemical methods. The global minimum on the potential energy surface corresponds to the chair conformer with axial nitro group, and the other two minima have been identified as chair conformer with equatorial nitro group and 2,5-twist. All transition states on the route of conformational transformations of the title molecule have been revealed.     

Synthesis of 6-halo-5-nitroquinoxalines

The 5-nitro derivatives of 6-haloquinoxalines have been efficiently synthesized by condensation of α-dicarbonyls with 4-bromo- or 4-chloro-3-nitro-1,2-benzenediamines. The novel diamines were readily obtained by reductive cleavage of 5-bromo- and 5-chloro-4-nitro-2,1,3-benzoselenadiazoles. As demonstrated by the synthesis of an imidazo-, a selenadiazolo- and a pyrazinoquinoxaline, the reactive halogen atom ortho to the nitro substituent renders the novel quinoxalines versatile intermediates to further heterocycles.     

二维配位聚合物[K2(5-nbdc)2Cd(Ⅱ)·imH·H2O]∞的合成和晶体结构(英)

The crystal structure of the title complex, [K₂(5-nbdc)₂Cd(Ⅱ)·imH·H₂O]_∞ (5-nbdc=5-nitro-1,3-benzenedicarbonate, imH=imidazole) has been determined by X-ray diffraction analysis. The crystal data are: tetragonal, space group P4₁, M_r=694.93 for CdC₁₉H₁₂N₄O₁₃K₂, a=1.018 6(10) nm, b=1.018 6(10) nm, c=2.436 7(5) nm; Z=4, V=2.528 2(6) nm³, F(000)=1 376, D_c=1.826 Mg·m^-3, μ=1.267 mm^-1. The title polymeric complex exhibits a two-dimensional framework, in which adjacent Cd(Ⅱ) ions are bridged by μ-O₄-5-nitro-1,3-benzenedicarbonate groups forming one-dimensional chains that are further linked by μ-O₃-5-nitro-1,3-benzenedicarbonate groups into two-dimensional anion rectangle sheets with large 32-membered rings. The strong π-π stacks of the benzene rings link these adjacent sheets into a three-dimensional van der Waals network. CCDC: 245527.     

Synthesis of 5-amino-6-nitro-1,2,3,4-tetrazine 1,3-dioxide

5-Amino-(tert-butyl-NNO-azoxy)-1,2,3,4-tetrazine 1,3-dioxide reacts with nitronium tetra-fluoroborate to give 5-amino-6-nitro-1,2,3,4-tetrazine 1,3-dioxide. This compound is of interest as a new energetic material. A plausible reaction mechanism involves electrophilic substitution of the tert-butyl-NNO-azoxy group by the nitro group.

     

Multistep nucleophilic substitution of the halogen atom in 2-halo-2-alkenals

pso-Substitution of the halogen atom in 2-halo-2-alkenals under the action of secondary amines proceedsvia three consecutive steps: addition, nucleophilic substitution, and -elimination (the Ad_N-S_N-E mechanism). The main intermediates arising in the reactions of 2-chloropropenal and 2-chloro-2-butenal with piperidine were detected by NMR spectroscopy. A general scheme of the reaction is proposed.Translated fromIzvestiya Akademii. Seriya Khimiicheskaya, No 1.pp. 139–142.January, 1996.     

Syntheses in the field of 5-nitro-2-furylpolyalkenals and 5-nitro-2-furylpolyalkenones

A series of, -bis(5-nitro-2-furyl)poryalkenones has been synthesized by the condensation of 5-nitro-2-furylalkenones with 5-nitrofuran aldehydes in acetic acid (concentrated sulfuric acid catalyst). In the , -bis(5-nitro-2-furyl)polyalkenone series, the keto group acts as a partial insulator of conjugation, which is shown most clearly in the case of 1,3-bis(5-nitro-2-furyl)prop-2-en-1-one and 1,5-bis(5-nitro-2-furyl)-penta-2,4-dien-1-one, i.e. compounds having the keto group directly linked to a 5-nitrofuran ring. The electronic spectra of the semicarbazones of the, -bis(5-nitro-2-furyl)polyalkenones exhibit a stronger disturbing effect of the conjugation in the molecule than in the case of the ketones, which may be connected with a disturbance of coplanarity. In a number of cases, the infrared spectra of the, -bis(5-nitro-2-furyl)polyalkenones exhibit splitting of the symmetrical and antisymmetrical vibrations of the nitro group.For part VII, see [1].Preliminary results of the present investigation were given for the first time at the 2-nd All-union Scientific Conference on the Chemistry of Furan Compounds, Saratov, 23–26 January, 1962, see [2].     

Cleavage of 2-(1,2,3,4-tetrahydroisoquinolin-1-yl)-2-phenyl-1,3-dithianes with HgO/BF3

Summary The title compounds (5) were prepared by addition of 2-phenyl-1,3-dithiane anion (2-lithiated10) to adequately substituted N-alkyl-3,4-dihydroisoquinolinium salts (7a–7g). Cleavage of compounds5 with HgO/BF₃ affords S-benzoyl-1,3-propanedithiol (4a) and the corresponding disulfide4c, benzaldehyde, and Hg(I) ions. In contrast to the title compounds, 2-(-dialkylaminobenzyl)-2-phenyl-1,3-dithianes (6) yield benzil under these conditions.In commemoration of the late Prof. Dr. Dr. h.c. mult.Horst Böhme, Marburg/Germany, an outstanding representative of Pharmaceutical Chemistry     

Alkenyl derivatives of 5-nitro-2-pyridone: Synthesis and halocyclization

Alkylation of 5-nitro-2-pyridone by alkenyl halides in acetone in the presence of K₂СО₃ proceeds with generation of a mixture of N- and О-derivatives with N-isomer prevailing. 1-Allyl- and 1-methylallyl-5-nitro-2-pyridone react with halogens with the formation of 2-halomethyl-6-nitro-2,3-dihydrooxazolo[3,2-a]-pyridinium halides. 1-Prenyl-5-nitro-2-pyridone reacts with bromine with the formation of 3-bromine-2,2-dimethyl-7-nitro-3,4-dihydro-2Н-pyrido[2,1-b][1,3]oxazinium bromide, and with iodine giving 2,2-dimethyl-7-nitro-3,4-dihydro-2Н-pyrido[2,1-b][1,3]oxazinium triiodide.     

Conformational transformations and autooxidation of 5-bromo-2-(2-methylpropyl)-5-nitro-1,3,2-dioxaborinane

Conformational study of 5-bromo-2-(2-methylpropyl)-5-nitro-1,3,2-dioxaborinane at the DFT PBE/3ξ level of theory revealed the only sofa–sofa interconversion pathway through a transition state corresponding to 2,5-twist conformer. The barrier to internal rotation of the axial nitro group is several times higher than that for the equatorial nitro group. According to the ¹H, ¹³C, and ¹¹B NMR, IR, and X-ray diffraction data, the main autooxidation products of 5-bromo-2-(2-methylpropyl)-5-nitro-1,3,2-dioxaborinane are 2-bromo-2-nitropropane-1,3-diol and boric acid.     

Optisch aktives 1,3-Diferrocenyl-1,3-diphenyl-allen

The title compound 2 was prepared by thermal dehydration of 1,3-diferrocenyl-1,3-diphenyl-propenol (24) with 70% yield.24 was accessible from 1,3-diferrocenyl-propanedione-1,3 (25) in two steps with 10% overall yield: Treatment of25 with phenyllithium gave 1,3-diferrocenyl-3-phenyl-propenone (8) which after repeated reaction with phenyllithium afforded24.Partial optical resolution of2 was achieved by chromatography on triacetyl cellulose in ethanol, whereby both (+)- and (–)-2 were obtained with different enantiomeric purities as could be deduced from the CD-spectra with -values of +0.18 and –1.64, resp., at 480 nm.Attempts to prepare 1,3-diferrocenyl-allene and 1,3-diferrocenyl-1-phenyl-allene failed. In this context several 1,3-diferrocenyl-propenols,-propenones,-propenes,-propanones,-propanes and-butadienes were obtained.

62. Mitt.:M. Benedikt undK. Schlögl, Mh. Chem.109, 805 (1978).     

Regio- and stereoselective 1,3-dipolar cycloaddition of arylnitrile oxides to 5-acetoxy-2(5H)-furanone

Summary Arylnitrile oxides undergo regio- and stereo-specific 1,3-dipolar cycloaddition reactions with 5-acetoxy-2(5H)-furanone. In each case a single product3a–3g results from ananti approach to the 5-acetoxy substituent, the oxygen of the 1,3-dipole being attached to C-4 of furan. Under similar conditions 5-benzoyloxy-2(5H)-furanone yields3h–3i. The structures of the adducts were determined by¹H- and¹³C-NMR spectroscopy.

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Regio- und stereoselektive 1,3-dipolare Cycloaddition von Arylnitriloxiden mit 5-Acetoxy-2(5H)-furanon

Zusammenfassung Arylnitriloxide reagieren mit 5-Acetoxy-2(5H)-furanon in einer regio- und stereoselektiven 1,3-dipolaren Cycloaddition. In jedem der untersuchten Fälle ergaben sich die einheitlichen Produkte3a–3g als Folge eineranti-Annäherung an den 5-Acetoxysubstituenten, wobei der Sauerstoff des 1,3-Dipols an das C-4 des Furans addiert. Unter ähnlichen Bedingungen ergab 5-Benzoyloxy-2(5H)-furanon die Produkte3h–3i. Die Strukturen der Addukte wurden mittels¹H-und¹³C-NMR bestimmt.

     

Mechanism of the electrochemical reduction of 2-halo-5-nitrothiophenes in dimethylformamide

The reduction of 2-bromo-5-nitrothiophene and 2-iodo-5-nitrothiophene in dimethylformamide (DMF) was studied by means of classical and commutated polarography, EPR spectroscopy, a rotating platinum disk electrode with a ring, and preparative electrolysis. It was established that, depending on the nature of the halogen, their anion radicals may undergo further reduction to 2-nitrothiophene anion radicals or decomposition with splitting out of a halide anion and conversion to nitrothienyl radicals, which were identified on the ring electrode. The latter are capable of undergoing dimerization to 2,2-dinitro-5,5-dithienyl. The spectra of the anion radicals of 2-nitrothiophene and 2,2-dinitro-5,5-dithienyl were recorded by means of EPR. A mechanism for the reduction of halonitrothiophenes is proposed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 195–198, February, 1981.     

A novel synthesis of spiro[(2,2-dimethyl-[1,3]-dioxane)-5,2′-(2′,3′-dihydroindole)] using SRN1 reaction conditions

A concise synthesis of the spiro[(2,2-dimethyl-[1,3]-dioxane)-5,2′-(2′,3′-dihydroindole)] nucleus from substituted benzyl chlorides and 5-(hydroxymethyl)-2,2-dimethyl-5-nitro-1,3-dioxane 5 as starting materials is reported. The nitro intermediates 6 and 7 were prepared under S_RN1 reaction conditions.     

1,3-Dipolar cycloaddition of phthalazinium ylides to 5-arylidene-2-spirocyclohexane-1,3-dioxane-4,6-diones

Tetrahydrospiropyrrolo[2,1-a]phthalazines were synthesized by the reaction of 5-arylidene-2-spirocyclohexane-1,3-dioxane-4,6-diones with phthalazinium ylides. One of the reaction products, viz., 3-ethoxycarbonyl-2-(4-methoxyphenyl)-2′,2′-pentamethylene-1,2,3,10b-tetrahydrospiro[pyrrolo[2,1-a]phthalazine-1,5′-[1,3]dioxane]-4′,6′-dione, was studied by X-ray diffraction. The spectroscopic characteristics of the reaction products are discussed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2362–2365, October, 2005.     

Oxidative cyclisation of chalcones with thallium(III)nitrate: Synthesis of (Z)-2-phenylmethylene-7-nitro-3(2H)-benzofuranones

Oxidation of 2-hydroxy-3-nitrochalcones with thallium(III) nitrate gives (Z)-2-phenylmethylene-7-nitrobenzofuran-3(2H)-one derivatives, rather than the more usual 1,2-diaryl-3,3-dimethoxypropan-1-ones or the corresponding isoflavones.

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Oxydative Cyclisierung von Chalconen mit Thallium(III)nitrat: Synthese von (Z)-2-Phenylmethylen-7-nitro-3(2H)-benzofuranonen (Kurze Mitteilung)

Zusammenfassung Die Oxidation von 2-Hydroxy-3-nitrochalconen mit Thallium(III)nitrat ergab (Z)-2-Phenylmethylen-7-nitro-3(2H)-benzofuranon-Derivate und nicht die üblichen 1,2-Diaryl-3,3-dimethoxypropan-1-one bzw. die entsprechenden Isoflavone.

     

Synthesis, structure, and photoisomerization of derivatives of 2-(2-quinolyl)-1,3-tropolones prepared by the condensation of 2-methylquinolines with 3,4,5,6-tetrachloro-1,2-benzoquinone

A series of novel derivatives of the 1,3-tropolone (β-tropolone) system—2-(2-quinolyl)-5,6,7-trichloro-1,3-tropolones and 2-(2-quinolyl)-4,5,6,7-tetrachloro-1,3-tropolones have been prepared by the acid-catalyzed reaction of 2-methylquinolines with 3,4,5,6-tetrachloro-1,2-benzoquinone. The molecular structures of two compounds, 2-(4-chloro-6,8-dimethyl-5-nitro-2-quinolyl)-5,6,7-trichloro-1,3-tropolone 8 and 2-(4-chloro-7,8-dimethyl-5-nitro-2-quinolyl)-4,5,6,7-tetrachloro-1,3-tropolone 9, have been determined using X-ray crystallography. According to the performed DFT B3LYP/6-311++G^∗∗ calculations the tautomeric (OH) and (NH) forms of β-tropolones 8 and 9 are nearly energy equivalent, the latter being more stabilized in polar media. Photolysis of 2-(2-quinolyl)-1,3-tropolones in heptane solution leads to the disrotatory electrocyclic rearrangement resulting in the formation of a mixture of E- and Z-isomers of 3-[2(1H)-quinolinylyden]-bicyclo[3.2.0]hept-6-en-2,4-dione derivatives.     

Zur konformativen Anordnung dipolarer Substituenten in 5-Stellung von 1,3-Dioxanen

Summary The conformation of a series of 5-nitro-1,3-dioxanes, 1,3-dioxane-5-hydroxylamines and the corresponding nitrones, obtained from the latter, has been studied by NMR spectroscopy. In the case of the nitrones, a preferred conformation of the -N(O)CHR ³ substituent to the C⁵, N single bond was found, and it was concluded therefrom on the identical conformational behaviour of the nitro analogoues. A structurally similar spiro compound confirms the suggestions given. In the case of the spiro compound, the intramolecular N-inversion process could be studied by dynamic NMR spectroscopy; the free energy of activation is given.

     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS—VI. IDENTIFICATION OF THE FREE RADICALS GENERATED DURING THE PHOTOLYSIS OF MUSK AMBRETTE, MUSK XYLENE AND MUSK KETONE

Musk ambrette (4-tert-butyl-3-methoxy-2,5-dinitrotoluene), a common component of perfumes, soaps, and some food flavorings, can cause cutaneous photosensitization reactions including photoallergy. These may be mediated through free radicals formed during photolysis. When musk ambrette was photolyzed under nitrogen in basic methanol, two distinct nitro anion radicals were identified by electron spin resonance. One radical was centered on a nitro group in the plane of the aromatic ring, while the other was centered on a nitro group twisted out of the plane of the ring due to steric hindrance by bulky substituents on either side of the group: the two radicals appeared to interconvert and maintain an equilibrium concentration ratio. Two closely related compounds which are also used in perfumes, but have not been reported to cause photosensitizing reactions, also produced free radicals during photolysis. Musk xylene (2,4,6-trinitro-1,3-dimethyl-5-tert-butylbenzene) generated two nitro anion radicals, both of which were centered on twisted nitro groups, while musk ketone (3,5-dinitro-2,6-dimethyl-4-tert-butylacetophenone) produced only one nitro anion radical, which is also twisted. Athough these nitro anion radicals are probably the first step in the photolysis of these nitroarornatic molecules, it seems likely that in vivo they will undergo further reduction to produce more reactive species including the corresponding nitroso and hydroxylamine derivatives. In addition, autoxidation of the nitro anion radical intermediate forms superoxide.     

Ringschlußreaktionen von 2-Acyl-1-chlor-enaminen mit thioamidfunktionellen Verbindungen: Wahlweiser Zugang in die 1,3-Thiazin- und 1,3-Oxazin-Reihe

2-Acyl-1-chloro-enamines2 react with thioureas to 2,6-diamino-1,3-thiazinium salts3, following the usual transformation mode of 1-heterosubstituted acylvinylchloridesA. On the other hand the reaction of2 with thiobenzamide preferably leads to 4-amino-1,3-oxazinium salts7. The last course is discussed in terms of imidoyl-migration in the primary productE formingF, which finally undergoes ring condensation. This assumption corresponds in the best way with all experimental findings, moreover with special model reactions (e.g.2 13).

Herrn Prof. Dr.Klaus Hafner zum 60. Geburtstag gewidmet.     

Dynamic modulation of fluorine isotropic hyperfine interaction in the 2-nitro-1,4-bis(trifluoromethyl)benzene radical anion in acetonitrile

We have performed measurements and numerical reconstruction of the temperature dependence of the EPR spectrum of the 2-nitro-1,4-bis(trifluoromethyl)benzene radical anion in anhydrous acetonitrile, caused by dynamic modulation of the fluorine isotropic hyperfine interaction by hindered internal rotation of the CF₃ group ortho to the nitro group. The activation energy of rotation is 34.2±0.76 kJ·mol^?1.