Synthesis and Molecular and Crystalline Structure of Polyfluoro-1,3-Diazafluorenes

Reactions of 2-amino-3-(1-imino-2,2,2-trifluoroethyl)hexafluoro-1H-indene with carboxylic acid anhydrides and chlorides afforded 2-alkyl(aryl)-4-trifluoromethyl-5,6,7,8,9,9-hexafluoro-1,3-diazafluorenes. The molecular and crystalline structure of the products was studied by NMR spectroscopy and X-ray diffraction. 5,6,7,8,9,9-Hexafluoro-2-phenyl-4-trifluoromethyl-1,3-diazafluorene in crystal gives rise to infinite ladder chains via -stacking interaction between the benzene ring of one molecule and tetrafluorobenzene fragment of the other.     

Crystal structure of 2-nitropyridine

The crystal structure of 2-nitropyridine has been determined by x-ray diffraction analysis. The influence of the nitro group on the geometric parameters of the molecule was evaluated, as well as its influence on the molecular parameters of other nitropyridines, depending on the position of this group in the pyridine ring. Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090. E-mail: gatilov@nioch.nsc.ru. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1367–1371, October, 1998.     

Investigation of conjugated dinitrones — derivatives of pyrroline oxide

The molecular structure of three derivatives ofbis(2- R- 5,5- dimethyl- 3- oxo- 1- oxide pyrrolin- 1- ylidene- 3),where R =CH ₃ (@#@5a @#@), C ₆H₅ (@#@5b @#@), C(CH ₃)₃ (@#@5c @#@), and of the complex of 5b with copper(II)hexafluoroacetylacetonate [Cu(hfac) ₂ (@#@5b @#@)] was investigated by X- ray diffraction analysis in the framework of our studies of the possible tautomeric equilibrium conjugated dinitrone ? nitroxide biradical. The pyrroline rings of the molecules under analysis are planar (rms deviations of atoms are no more than 0.041 å), and the interplanar angles are 32.01(5), 42.84(9), and 51.45(7)? for 5a,5b,and 5c,respectively. It is established that the bond lengths of the C(2)- C(3) =C(3a)- C(2a) fragment are equalized to C(2)- C(3) 1.42 and C(3)- C(3a) 1.40 å. The N→O bond lengths of the nitrone group are within 1.250(4)- 1.282(4) å) [in Cu(hfac)₂ (5b)]. The geometrical data obtained do not permit us to make an unambiguous choice between the tautomeric structures. The magnetic susceptibility measurements of the Cu(hfac)₂ solid complex (5b) and the absence of paramagnetism in solid compounds 5 indicate that they are diamagnetic.     

Transformations of conjugated enamines of the imidazolidine 1-oxide series in the Vilsmeier-Haack reaction

In some cases, the reactions of enaminones of the imidazolidine 1-oxide series with the Vilsmeier reagent afford electrophilic substitution products containing the dimethyl-aminomethylene group. In an acidic medium, these products undergo either hydrolytic elimination of the dimethylaminomethylene moiety or hydrolysis of the latter to form the aldehyde group. The reaction of nitroenamine, which is a derivative of imidazolidine 1-oxide, with the Vilsmeier reagent produces furoxane, viz., the nitroxyl biradical. Reduction of the latter affords the dioxime biradical. Dedicated to the memory of Academician N. N. Vorozhtsov on the 100th anniversary of his birth. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1165–1170, June, 2007.     

Photochemical synthesis of 1,2,3,4,5,6,8,9-octamethyl-C2V-bishomocubane

1,2,3,4,5,6,8,9-Octamethyl-C_2V-bishomocubane was prepared by the photochemical cyclization of 1R,3S,4,5,6R,8S,9,10-octamethyltricyclo[6.2.0.0^3,6]deca-4,9-di-ene in benzene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1440–1442, June, 1991.The authors express their gratitude to V. I. Eroshkin for a number of valuable suggestions for carrying out the photochemical experiments.     

Crystal and molecular structure of 6b,7,8,8a-tetramethyl-6b,8a-dihydrocyclobut[a]acenaphthylene and 1,2,2a,10b-tetramethyl-2a,10b-dihydrocyclobuta[l]phenanthrene

The crystal and molecular structure of 6b,7,8,8a-tetramethyl-6b,8a-dihydrocyclobut[a]acenaphthylene (I) and 1,2,2a,10b-tetramethyl-2a,10b-dihydrocyclobuta[l]phenanthrene (II) is established by XRD analysis. The C(6b)-C(8a) bond in I is lengthened to 1.603(3) ∢, and the C(2a)-C(10b) bond in II is prolonged to 1.589(6) ∢. The acenaphthene and dihydrophenanthrene frameworks are planar; the rms deviations of atoms from the plane are 0.011 and 0.032 ∢, respectively. Translated fromZhurnal Strukturnoi Khimii, Vol. 38, No. 6, pp. 1140–1145, November–December, 1997.     

Synthesis, structure, and X-band (9.5 GHz) EPR characterization of the new series of pH-sensitive spin probes: N,N-disubstituted 4-amino-2,2,5,5-tetramethyl-3-imidazoline 1-oxyls

[reaction: see text] An approach to the synthesis of new imidazoline nitroxides bearing an N',N'-disubstituted amidine group is reported. The approach is based on the alkylation of diamagnetic 4-R-amino-1,2,2,5,5-pentamethyl-3-imidazolines with bromoacetic acid ethyl ester; the products of alkylation are further oxidized to the corresponding nitroxides. The approach allows a variety of functional groups to be introduced into the nitroxide molecule structure. Alkylation with bromoacetic acid ethyl ester was found to proceed with high regioselectivity and afford the products of exo-alkylation. The regiochemical assignment is made on the basis of 13C NMR spectra and confirmed by X-ray diffraction study. All of the nitroxides synthesized here were shown to have pH-dependent EPR spectra with pKa ranging from 3.5 to 6.2. For nitroxides 13 bearing the carboxylic group remote to the nitroxide moiety, the changes in isotropic magnetic parameters of EPR spectra due to reversible deprotonation of the carboxylic group were found to be small. For these nitroxides, we demonstrate an alternative approach for pKa determination that is based on measuring the peak-to-peak line width of the EPR spectrum in the presence of the paramagnetic broadening agent potassium ferricyanide. The partition coefficients of nitroxides in octanol/H2O and octanol/phosphate buffer solution mixtures were measured to reveal a range of their lipophilicities.     

Synthesis of annelated derivatives of tetrafluoro-10<Emphasis Type="Italic">H</Emphasis>-imidazo[1,2-<Emphasis Type="Italic">b</Emphasis>][1,2]benzooxazin-10-one and 2-pentafluorophenylpyrazine 1,4-dioxide by condensation of alicyclic 2-hydroxyamino oximes with pentafluorophenylglyoxal

Reactions of alicyclic 2-hydroxyamino oximes with pentafluorophenylglyoxal afford mixtures of annelated derivatives of 2-pentafluorophenylpyrazine 1,4-dioxide and tetrafluoro- 10H-imidazo[1,2-b][1,2]benzooxazin-10-one. The structures of the latter were established by X-ray diffraction analysis.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1636–1639, August, 2004.     

Sesquiterpene Lactones from <Emphasis Type="Italic">Stizolophus balsamita</Emphasis> and Their Biological Activity

Four sesquiterpene lactones with the germacrane structure were isolated from the aerial part of Stizolophus balsamita. X-ray structure analyses showed that two of them were previously known balsamin derivatives. A third was a crystalline isomorphous mixture of the known lactone stizolin and 11,13-dihydrostizolin in a 53:47 ratio. The biological activities of the balsamin derivatives were investigated. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 454–457, September–October, 2005.     

Synthetic Transformations of Higher Terpenoids. 41. Synthesis and Anti-Inflammatory Activity of 4-(Carboxyalkyl)-18-nor-isopimara-7,15-Dienes

Chemistry of Natural Compounds - Synthetic methods were developed for isopimaric acid derivatives, the terminal carboxylic acid of which was separated by two or three methylenes from the tricyclic...