α-Acetylenic ethyleneimides and their reactions with amines

The reaction of aziridines with phenyl and p-chlorophenylpropiolyl chlorides at —30 to 60°C leads only to 1,2-addition products, viz., -acetylenic ethyleneimides, or their isoraerization products, viz., 2-ethynyl-substituted 2-oxazolines. Reactions with amines showed that the p-chlorophenylpropiolic acid ethyleneimides obtained are mild N-acylating agents.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1064–1067, August, 1980.     

Corrosion-protective properties of 1-phenacylmethyl-2-arylcarbamido(arylthiocarbamido)pyridinium bromides

Inhibiting effect of 1-phenacylmethylpyridinium bromides containing urea or thiourea substituents in the pyridinium ring on steel and zinc corrosion in sulfuric acid solutions was studied.     

2-Ethynylaziridines

Methods for the synthesis of 2-ethynylaziridines by the cycloaddition of carbene to an -ethynyl imine, cyclization of acetylenic -amino alcohols in the presence of triphenylphosphine, and by means of the Gabriel reaction were developed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 184–187, February, 1984.     

Hydrogen bonding and proton transfer involving the trihydride complexes Cp*M(dppe)H3 (M = Mo,W) and fluorinated alcohols: the competitive role of the hydride ligands and metal

The protonation of complexes Cp*M(dppe)H₃ (dppe is ethylenebis(diphenylphosphine), M = Mo (1), W (2)) by a variety of fluorinated alcohols of different acid strength (FCH₂CH₂OH, CF₃CH₂OH, (CF₃)₂CHOH, and (CF₃)₃COH) was investigated experimentally by the variable temperature spectroscopic methods (IR, NMR) and stopped-flow technique (UV-Vis). The structures of the hydrogen-bonded and proton transfer products were studied by DFT calculations. In agreement with the calculation results, the IR data suggest that the initial hydrogen bond is established with a hydride site for complex 1 and with the metal site for complex 2. However, no intermediate dihydrogen complex found theoretically was detected experimentally on the way to the final classical tetrahydride product.     

Steroid compounds of marine sponges

A new sulfated steroid triol — 26-norsokotrasterol sulfate — has been identified in extracts of the sponge(Trachyopsis halichondroides). Its structure has been shown as 24,25,26-trimethyl-5-cholest-23-ene-2, 3, 6-triol trisulfate. No steroid substances with side chains having the structure of that in 26-norsokotrasterol sulfate have previously been found.Pacific Ocean Institute of Bioorganic Chemistry. Far Eastern Branch, USSR Academy of Sciences, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii. No. 3. pp. 371–375, May–June, 1988.     

Experimental and computational studies of hydrogen bonding and proton transfer to [Cp*Fe(dppe)H

The present contribution reports experimental and computational investigations of the interaction between [Cp*Fe(dppe)H] and different proton donors (HA). The focus is on the structure of the proton transfer intermediates and on the potential energy surface of the proton transfer leading to the dihydrogen complex [Cp*Fe(dppe)(H2)]+. With p-nitrophenol (PNP) a UV/Visible study provides evidence of the formation of the ion-pair stabilized by a hydrogen bond between the nonclassical cation [Cp*Fe(dppe)(H2)]+ and the homoconjugated anion ([AHA]-). With trifluoroacetic acid (TFA), the hydrogen-bonded ion pair containing the simple conjugate base (A-) in equilibrium with the free ions is observed by IR spectroscopy when using a deficit of the proton donor. An excess leads to the formation of the homoconjugated anion. The interaction with hexafluoroisopropanol (HFIP) was investigated quantitatively by IR spectroscopy and by 1H and 31P NMR spectroscopy at low temperatures (200-260 K) and by stopped-flow kinetics at about room temperature (288-308 K). The hydrogen bond formation to give [Cp*Fe(dppe)H]HA is characterized by DeltaH degrees =-6.5+/-0.4 kcal mol(-1) and DeltaS degrees = -18.6+/-1.7 cal mol(-1) K(-1). The activation barrier for the proton transfer step, which occurs only upon intervention of a second HFIP molecule, is DeltaH(not equal) = 2.6+/-0.3 kcal mol(-1) and DeltaS(not equal) = -44.5+/-1.1 cal mol(-1) K(-1). The computational investigation (at the DFT/B3 LYP level with inclusion of solvent effects by the polarizable continuum model) reproduces all the qualitative findings, provided the correct number of proton donor molecules are used in the model. The proton transfer process is, however, computed to be less exothermic than observed in the experiment.     

Preparation and properties of stable protonation products of permethylmetallocenecarbaldehydes (M = Fe,Ru, Os)

The products ofO-protonation of metallocenecarbaldehydes C₅Me₅MC₅Me₄CHO (M = Fe, Ru, Os) with HBF₄ and CF₃COOH were obtained for the first time, the adducts [C₅Me₅MC₅Me₄CH(OH)]⁺BF^– being isolated in a pure state. The structures of the adducts depend on the nature of the metal and the anion and are governed by the correlation between their basicities. For example, the Fe-containing adducts have an open fulvenoid structure with an interionic hydrogen bond irrespective of the nature of the anion X (X = BF₄ ^–, CF₃COO^–). In the case of the Ru- and Os-containing adducts in which the metal atoms are more basic than iron, the competition between the metal atom and the anion for the formation of a hydrogen bond with the OH group is clearly manifested in the IR and¹H NMR spectra. In the presence of the weakly basic BF₄ ^– anion, a cyclic structure with an intramolecular M...HO hydrogen bond is formed, while in the presence of a more basic F^– or CF₃COO^– anion. it transforms to the open fulvenoid structure with an interionic hydrogen bond. The structures of the compounds obtained were determined by IR and¹H NMR spectra, and the structure of the (C₅Me₅RuC₅Me₄CHOH)⁺...F^– salt was proved by X-ray diffraction analysis.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No.12, pp. 2486–2493, December, 1995.The work was carried out with financial support of the International Science Foundation (Grant Nos. JFN-100 and NSAW 000), the Russian Foundation for Basic Research (Grant No. 93-03-4610), and the Ministry of Science and Technical Policy of RF, whom the authors wish to thank.     

Steroid compounds of marine sponges. III. 24-Ethyl-25-methylcholesta-5,22-dien-3β-OL — A new marine sterol from the spongeHalichondria sp.

A new sterol — 24 ethyl-25-methylcholesta-5,22-dien-3β-ol — has been isolated by column chromatography on silica gel from extracts of the spongeHalichondria sp. Its structure has been established on the basis of an analysis of GLC-MS results and of PMR and¹³C NMR spectroscopy and has been confirmed by ozonolysis.     

Adjustment of numerical models for gamma-ray spectra of samples when subtracting spectra of matrix elements in neutron activation analysis

Approaches to adjustment of numerical models for gamma-ray spectra of matrix elements are considered. These approaches are aimed at (1) the elimination of the substrate effect in the preparation of the initial spectra of individual elements, (2) the energy calibration of spectra, (3) the improvement of agreement between model and actually observed spectra using the comparison test for peak amplitudes of matrix elements, and (4) special processing of the spectra obtained after the subtraction of matrix elements in the test samples. The adjustment allows the contribution of matrix elements to be more precisely subtracted from the spectra of the samples under study. Thus, additional analytical lines are obtained for some elements, and detection limits are lowered for the majority of lines produced by the standard method of spectrum processing. This extends the potential of neutron activation analysis in solving scientific and practical problems.     

Influence of media and homoconjugate pairing on transition metal hydride protonation. An IR and DFT study on proton transfer to CpRuH(CO)(PCy3)

The interaction of the ruthenium hydride complex CpRuH(CO)(PCy(3)) (1) with proton donors HOR of different strength was studied in hexane and compared with data in dichloromethane. The formation of dihydrogen-bonded complexes (2) and ion pairs stabilized by hydrogen bonds between the dihydrogen ligand and the anion (3) was observed. Kinetics of the interconversion from 2 to 3 was followed at different (CF(3))(3)COH concentrations between 200 and 240 K. The activation enthalpy and entropy values for proton transfer from the dihydrogen-bonded complex 2 to the (eta(2)-H(2))-complex 3 (DeltaH() = 11.0 +/- 0.5 kcal/mol and DeltaS() = -19 +/- 3 eu) were obtained for the first time. The results of the DFT study of the proton transfer process, taking CF(3)COOH and (CF(3))(3)COH as a proton donors and introducing solvent effects in the calculation with the PCM method, are presented. The role of homoconjugate pairs [ROHOR](-) in the protonation is analyzed by means of the inclusion of an additional ROH molecule in the calculations. The formation of the free cationic complex [CpRu(CO)(PCy(3))(eta(2)-H(2))](+) is driven by the formation of the homoconjugated anionic complex [ROHOR](-). Solvent polarity plays a significant role stabilizing the charged species formed in the process. The theoretical study also accounts for the dihydrogen release and production of CpRu(OR)(CO)(PCy(3)), observed at temperatures above 250 K.