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81.
Badorrey R Cativiela C Díaz-de-Villegas MD Díez R Galbiati F Gálvez JA 《The Journal of organic chemistry》2005,70(24):10102-10105
[reaction: see text] Addition of trimethylsilyl cyanide to ketimines derived from (R)-2,2-dimethyl-1,3-dioxolan-4-yl methyl ketone to generate a quaternary stereocenter has been achieved with high yields and excellent diastereoselectivity. The stereoselectivity was found to be temperature and solvent dependent. The beta-hydroxy-alpha-amino nitrile of syn configuration was the major compound in kinetically controlled reactions, whereas the anti stereoisomer was obtained in excess in thermodynamically controlled reactions. Double stereodifferentiation under kinetic control conditions was successful, and the cyanation reaction occurred with complete syn diastereoselectivity using the matched pair. The versatility of the resulting amino nitrile as a synthetic intermediate was tested by performing the synthesis of orthogonally protected (R)-(2-aminomethyl)alanine. 相似文献
82.
Gupta Madan Mohan Srivastava Alpana Tripathi Arvind Kumar Misra Himanshu Verma Ram Kishore 《平面色谱法杂志一现代薄层色谱法》2006,19(4):282-287
JPC – Journal of Planar Chromatography – Modern TLC - High-performance thin-layer chromatography (HPTLC) has been used for normal-phase separation of the components of hexane,... 相似文献
83.
[reaction: see text] Optically pure allylic amines have been synthesized from alpha,beta-unsaturated aldehydes via allylboration with (-)-B-allyldiisopinocampheylborane, followed by Overman rearrangement. By incorporating crotyl and alkoxyallylboration, functionalization at delta-position was readily accomplished. By applying this methodology, the synthesis of several chiral alpha-amino acids has been achieved. 相似文献
84.
Surface tensions (sigma) for [1,3-dioxolane+methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and 1-pentanol] and excess molar volumes (v(E)) for [1,3-dioxolane+methanol, ethanol, 1-propanol, 2-propanol, and 2-butanol] at the temperature 298.15 K and normal atmospheric pressure have been determined as a function of mole fractions. The magnitude of these experimental quantities is discussed in terms of the nature and type of intermolecular interactions in binary mixtures. In order to analyze the surface tension behavior, the extended Langmuir (EL) model was used and the results obtained for the systems containing 1,3-dioxolane were compared with those of other formerly published series: [1,4-dioxane+alkanes] and [1,4-dioxane+alcohols]. 相似文献
85.
Rajendra Singh?Ghadwal Ram?C.?Mehrotra Anirudh?SinghEmail author 《Transition Metal Chemistry》2005,30(7):836-844
An entirely new class of heterobimetallic homoleptic glycolate complexes of the type Nb(OGO)3{Ta(OGO)2} [where G=CMe2CH2CH2CMe2 (G1) (3); CMe2CH2 CHMe(G2) (4); CHMeCHMe (G3) (5); CH2CMe2CH2 (G4) (6); CMe2CMe2(G5) (7); CH2CHMeCH2 (G6) (8); CH2CEt2CH2 (G7) (9); CH2CMe(Prn)CH2 (G8) (10)] have been prepared by the reactions of Nb(OGO)2(OGOH) [G=G1 (1a); G2 (1b); G3 (1c); G4 (1d); G5 (1e); G6 (1f); G7 (1g); G8 (1h)] with Ta(OGO)2 (OPri) (G=G1 (2a); G2 (2b); G3 (2c); G4 (2d); G5 (2e) G6 (2f); G7 (2g); G8 (2h). In addition to the novel derivatives (2)–(10), our earlier investigations on heterobimetallic glycolate-alkoxide derivatives have been extended to derivatives of the type
Nb(OGO)
[where M=A1 n=3, G=G3 (11);G4 (12); G6 (13) G7 (14); Gs (15); G9=CH2CH2CH2 (16) and M=Ti (n=4, G=G4) (17), Zr(n=4,G=G4) (18)], which are conveniently prepared by the reactions of metalloligands Nb(OGO)2(OGOH) [G=G3 (1c); G4 (1d); G6 (1f); G7 (1g); G8 (1h); G9 (1i)] with different metal alkoxides. All of these new complexes have been characterized by elemental analyses, molecular weight
determinations, and spectroscopic (I.r. and 1H, 27Al-n.m.r.) studies. Structural features of the new derivatives have been elucidated on the basis of molecular weight and spectroscopic
data. 相似文献
86.
11 and 12 molar reactions of dioxouranium(VI) acetate dihydrate with the monobasic bidentateSchiff bases,o-HOC6H4CH=NR oro-HOC10H6CH=NR (R=C2H5,n-C3H7,n-C4H9 or C6H5) and bibasic tridentateSchiff bases,o-HOC6H4CH=NR(OH) oro-HOC10H6CH=NR(OH) (R=–CH2CH(CH3)- or —CH2CH2CH2–) have been studied and derivates of the type UO2(OAc)2(SBH), UO2(OAc)2(SBH)2, UO2(OAc)2(SBH
2) and UO2(OAc)2(SBH
2)2 (whereSBH andSBH
2 represent monobasic bidentate and bibasic tridentateSchiff base molecules respectively) have been isolated. These have been characterized by elemental analysis, conductance measurements and IR spectral studies.
UO2 2+-Komplexe von Schiff-Basen. VII. Uranylacetat-Komplexe mit monobasischen zweizähnigen und bibasischen dreizähnigen Schiff-Basen
Zusammenfassung Es wurden in 1:1- und 1:2-molaren Reaktionen von UO2(OAc)2·2H2O mitSchiff-Basen (L) Komplexe des Typs UO2(OAc)2 L bzw. UO2(OAc)2 L 2 isoliert. Die Komplexe wurden mittels Elementaranalyse, Leitfähigkeitsmessungen und IR-Spektren untersucht.相似文献
87.
α-(N-Carbamoyl)alkylcuprates [R2CuLi·LiX or RCuXLi (X=CN, Cl)] when prepared from THF soluble CuX·2LiCl (X=Cl, CN) undergo a reliable and generally high yield reaction with aroyl, alkanoyl, and alkenoyl chlorides to provide a rapid and efficient synthesis of α-carbamoyl ketones. Cuprates prepared from acyclic, cyclic, and a functionalized carbamate can be utilized. Although yields are a function of cuprate reagent and substrate structure, nearly quantitative yields can be obtained with reagents generated from 2RLi+CuCN·2LiCl. The use of reagents generated from CuCl·2LiCl are more efficient in the α-(N-carbamoyl)alkyl ligand, although yields are slightly lower. Acylation of alkyl(chloro)cuprates generated from one equivalent of CuCl·2LiCl and organolithium or Grignard reagents provides an efficient and high yield procedure for ketone synthesis. 相似文献
88.
V. Balek L. A. Pérez-Maqueda J. Poyato Z. Černý V. Ramírez-Valle I. M. Buntseva J. L. Pérez-Rodríguez 《Journal of Thermal Analysis and Calorimetry》2007,88(1):87-91
The effect of grinding
on thermal behavior of pyrophyllite and talc as commonly used ceramic clay
minerals was investigated by DTA, TG, emanation thermal analysis (ETA), B.E.T.
surface area (s.a.) measurements, X-ray diffraction (XRD) and scanning electron
microscopy (SEM).
A vibratory mill was used in this study, grinding
time was 5 min. It was found that the grinding caused an increase in surface
area and a grain size reduction of the samples. From TG and DTA results it
followed that grinding caused a decrease of the temperature at which the structure
bound OH groups released. The formation of high temperature phases was enhanced
with the ground samples. For the ground talc sample the crystallization of
non-crystalline phase into orthorhombic enstatite was observed in the range
of 800°C. For ground pyrophyllite a certain agglomeration of grains was
observed in the range above 950°C. Moreover, for both clays the ETA characterized
a closing up of subsurface irregularities caused by grinding as a decrease
of the emanation rate in the range 250–400°C. The comparison of
thermal analysis results with the results of other methods made it possible
to better understand the effect of grinding on the ceramic clays. 相似文献
89.
Ram C. Maurya Dinesh C. Gupta Rajesh Shukla Raj K. Shukla Nalmas Anandam Mannar R. Maurya 《Transition Metal Chemistry》1986,11(12):463-464
Summary A new series of cyano-substituted nitrosylchromium(I) complexes having octahedral stereochemistry around the metal ion, and of general formula, [CrNO(CN)2(L)2(H2O)] (L =o-,m- andp-phenetidines oro-,m-, andp-anisidines) have been isolated in the solid state by interaction of potassium pentacy-anonitrosylchromate(I) monohydrate with the appropriately substituted aniline. The complexes, which have been characterised by elemental analysis, conductance, molecular weight determination, magnetic measurements, e.s.r. and i.r. spectral studies, contain chromium(I) in a low-spin d5-configuration. 相似文献
90.
Balderas-Hernández P Rojas-Hernández A Galván M Ramírez-Silva MT 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(3):569-577
The detailed analysis of the experimental spectrophotometric data obtained from solutions containing the acid-base indicator thymol blue (TB) and mercury(II) (Hg(II)) coupled with data processing by means of the SQUAD program, a chemical model was determined that includes the formation of complexes indicator-metal ion (HgTB and HgOTB), dimer species (H3TB2 and H4TB2) and monomer species (HTB and TB). The values of the overall formation constants (log beta) were calculated for the chemical equilibria involved: TB+Hg<-->HgTB log beta=16.047 +/- 0.043, TB+Hg+H2O<-->HgOHTB+H log beta=7.659 +/- 0.049, 2TB+4H<-->H4TB2 log beta=31.398 +/- 0.083, 2TB+3H<-->H3TB2 log beta=29.953 +/- 0.084 and H+TB<-->HTB-log beta=8.900. To compliment the present research, the values of the absorptivity coefficients are included for all the species involved, within a wide range of wavelengths (250-700 nm). The latter were used subsequently to carry simulations of the absorption spectra at various pH values, thus corroborating that the chemical model proposed is fully capable to describe the experimental information. Voltammetric study performed evidenced the formation of a complex with a 1:1 stoichiometry Hg(II):TB. 相似文献