Gas chromatographic study of acetyl derivates of chlorinated guaiacols

Summary The gas chromatography of acetyl derivatives of guaiacol and all chlorinated guaiacols has been studied on SE-30, OV-351 and Carbowax 20M capillary columns. The retention order and relative retention times under isotermal and temperature-programmed conditions are discussed. Different retention times for all mono- and dichloro compounds have been observed on the SE-30 column. However, all trichloroguaiacol isomers were separated only on polar columns. The best overall temperature-programmed separations have been achieved on an SE-30 capillary column.     

A study of the physico-chemical properties of 1,3,5-trihydroxy-1,3,5-triazin-2,4,6[1H,3H,5H]-trione

Acetyl (Ia) and pivaloyl (Ib) triesters of the 1N,3N,5N-trihydroxy-1,3,5-triazin-2,4,6[1H,3H,5H]-trione (I) were synthesised. The spectrophotometric and potentiometric investigation of I revealed a weak acidic properties of triprotonic acid (pK_a1=5.23, pK_a2=6.32, and pK_a3=7.93). The MS and TGA analyses of I indicated on hydroxyisocyanate as possible degradation product. The chelating ability of I with Fe(III)-ion was preliminary explored. IR measurements of aqueous solutions of I in the presence of Fe(III) ion showed the possible chelating ability of all hydroxamic moieties. The chemical structures and properties of investigated compounds were derived from the results of IR, ¹H and ¹³C NMR, UV and MS spectrometric data, as well as thermogravimetric and potentiometric analysis.     

Platina-β-diketones as catalysts for hydrosilylation and their reactivity towards hydrosilanes

The platina-β-diketones [Pt₂{(COMe)₂H}₂(μ-Cl)₂] (1), [PPh₄][Pt{(COMe)₂H}Cl₂] (2) and [Pt{(COMe)₂H}-(acac)] (3) were found to catalyze the hydrosilylation of alkynes (hex-1-yne, hex-2-yne, hex-3-yne) and alkenes (hex-1-ene, styrene, trimethylvinylsilane) with methyldiphenylsilane (n_silane:n_substrate:n_Pt = 3000:3000:1, T = 27 °C, in C₆D₆). The comparison with the well-established catalysts from Speier (4) and Karstedt (5) exhibited up to twice as high activities for catalyst 1 and comparable regioselectivities. To get insight into the mechanism of the hydrosilylation, Si-H oxidative addition reactions towards the dinuclear platina-β-diketone 1 have been explored. Reactions of 1 with 2-picolyl substituted hydrosilanes of the type NSiMe₂H and NSiMeHN resulted in decomposition with the formation of platinum black, only. On the other hand, the analogous reaction with the 8-quinolyl substituted silane of the type NSiMeHN was found to proceed under loss of H₂ with the formation of a diacetyl(silyl)platinum(IV) complex [Pt(COMe)₂Cl(NSiMeN-κ²N,N′,κSi)] (23). DFT calculations gave insight into the reason for this different reactivity and into the course of reaction. For comparison, the reaction of 1 with bis(2-picolyl)amine was performed resulting under proton shift in the sense of an oxidative addition reaction in the formation of the diacetyl(hydrido)platinum(IV) complex [Pt(COMe)₂Cl(NNHN-κ³N,N′,N′′)] (25). The complexes 23 and 25 were fully characterized spectroscopically (¹H, ¹³C, ¹⁹⁵Pt, ²⁹Si NMR, IR) and by single-crystal X-ray structure determinations.     

狗枣猕猴桃叶化学成分研究(Ⅱ)

从狗枣猕猴桃叶中分离出4个新的黄酮类化合物, 经1D NMR, 2D NMR及ESI-MS等波谱分析鉴定了其结构, 分别是4'-甲氧基-槲皮素-7-O-(4"-O-乙酰基-鼠李糖基)-3-O-β-D-吡喃葡萄糖苷(1), 山柰甲黄素-7-O-(3"-O-乙酰基-鼠李糖基)-3-O-芸香糖苷(2), 山柰酚-7-O-(4"-O-乙酰基-鼠李糖基)-3-O-芸香糖苷(3)和4'-甲氧基-槲皮素-7-O-(4"-O-乙酰基-鼠李糖基)-3-O-芸香糖苷(4).     

Fabrication of Nanocomposite Containing Naphthoquinone and Nanogold Supported on Poly(2,6‐pyridinedicarboxylic acid) Film for Voltammetric Determination of N‐Acetyl‐L‐Cysteine

A modified electrode was fabricated by grafting of poly (2,6‐pyridinedicarboxylic acid) film (PDC) by electropolymerization of 2,6‐pyridinedicarboxylic acid on the glassy carbon electrode (GCE). Then, gold nanoparticles (NG) and 1,2‐naphthoquinone‐4‐sulfonic acid sodium (Nq) were immobilized on the PDC/GCE to prepare Nq/NG/PDC/GCE by immersing electrode into NG and Nq solution, respectively. The Nq species on NG/PDC/GCE could catalyze electrooxidation of N‐acetyl‐L ‐cysteine (NAC) with lowering the over potential by about 600 mV. This method used for detection of NAC in dynamic range from 4.0×10^?6 M to 1.30×10^?4 M with a detection of limit (2σ) 8.0×10^?7 M.     

Scaled quantum chemical studies of the structural and vibrational spectra of acetyl coumarin

The solid phase FT-IR and FR-Raman spectra of acetyl coumarin have been recorded in the regions 4000–50 cm⁻¹. The spectra were interpreted with the aid of normal coordinate analysis following full structure optimization and force field calculations based on density functional theory (DFT) and Hartree-Fock (HF) at 6–31G* and 6–311++G** basis sets. The resulting force fields were transformed to internal coordinates, the calculated vibrational frequencies and normal modes were utilized in the assignment of the observed vibrational fundamentals. The measured spectral data were used to refine the vibrational force constants by means of a small number of scaling factors.     

Untersuchungen über Chinone, 9. Mitt. Über Acetylderivate vonp-Indazolchinonen

Summary Acetylation of the indazolquinones1a (6-anilino-),b (6-p-toluidino-),c (6-N-methylanilino-),g (6- or 5-methylthio-), andk (benz[f]-) by heating with acetic anhydride yields the 2-acetylindazolquinones4a, b, c, g, andk. Reductive acetylation of the quinones1c, g, h/h ₁(6/5-methyl),k and — for structure elucidation — their 1-N- (2c) and 2-N- (3c, 3e)-methyl derivatives with acetic anhydride, zink powder, and sodium acetate gives the 1-acetyl-(7c, g, h/h ₁,k), resp. 1-methyl- (8c), and 2-methyl- (9c, e) diacetoxyindazoles. In case of1k, two diacetyl derivatives were isolated in addition to the already known triacetyl derivative7k, regardless of the conditions chosen. Acetylation of the intermediate product of the reaction from phenylthio-benzoquinone with diazomethane also yields a triacetyl-hydroquinone (7f). UV/Vis, IR, and¹H NMR spectroscopy were used for structure determination. Comparison of the UV/Vis spectra of the acetyl derivatives4 with those of1, 2, 3, and of compounds7 with those of analog substituted indazols shows that the acetyl group is located in position 2 with compounds4 and in position 1 with compounds7. By means of¹H NMR spectra the position of the acetyl group can be determined by the effect of the carbonyl group on the proton in position3.

     

Experimental and theoretical FMO interaction studies of the Diels-Alder reaction of 5-acetyl-3-methythio-1,2,4-triazine with cyclic enamines

Diels-Alder reaction of 5-acetyl-3-methylthio-1,2,4-triazine with five cyclic enamines has been reinvestigated in its preparative and theoretical aspects. Its regioselectivity has been developed practically, which is in agreement with theoretical consideration of the FMO interactions, including secondary orbital interactions in the transition state. Since the energetic demands are similar for all five pairs, it has been indicated that their reactivity differences can be explained by an influence of steric hindrance in the considered transition state. In result, the synthesis of the 3-acetyl-1-methylthiocycloalka[c]pyridines, as synthons for preparation of sempervirine and its analogues has been optimized. The subsequent side reaction has been detected as a serious problem, especially in the case of the six-membered enamine, which reacts with the acetyl group of the final product formed in the reaction mixture.     

Reactivity of cationic methyl rhodium(III) complexes cis-[Rh(β-diket)(PPh3)2(CH3)(CH3CN)][BPh4] toward ligands of different character: pyridine, carbon monoxide, and triphenylphosphine

Cationic methyl complex of rhodium(III), cis-[Rh(Acac)(PPh₃)₂(CH₃)(Py)][BPh₄] (1) as a single isomer with Py in the trans to PPh₃ position, is formed upon the reaction of cis-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] with pyridine in methylene chloride solution.Complex 1 was characterized by elemental analysis and by ³¹P{¹H} and ¹H NMR spectra.Cationic pentacoordinate acetyl complexes, trans-[Rh(Acac)(PPh₃)₂(COCH₃)][BPh₄] (2) and trans-[Rh(BA)(PPh₃)₂(COCH₃)][BPh₄] (3), are prepared by action of carbon monoxide on cis-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] and cis-[Rh(BA)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄], respectively, in methylene chloride solutions.Complexes 2 and 3 were characterized by elemental analysis and by IR, ³¹P{¹H}, ¹³C{¹H} and ¹H NMR. According to NMR data, 2 and 3 in solution are non-fluxional trigonal bipyramids with β-diketonate and acetyl ligands in the equatorial plane and axial phosphines.In solutions, 2 and 3 gradually isomerize into octahedral methyl carbonyl complexes trans-[Rh(Acac)(PPh₃)₂(CO)(CH₃)][BPh₄] (4) and trans-[Rh(BA)(PPh₃)₂(CO)(CH₃)][BPh₄] (5), respectively.Complexes 4 and 5 were characterized by IR, ³¹P{¹H}, ¹³C{¹H} and ¹H NMR, without isolation.Upon the action of PPh₃ on cis-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] and cis-[Rh(BA)(PPh₃)₂(CH₃)(CH₃CN)] [BPh₄], reductive elimination of the methyl ligand as a phosphonium salt, [CH₃PPh₃][BPh₄], occurs to give square planar rhodium(I) complexes [Rh(Acac)(PPh₃)₂] and[Rh(BA)(PPh₃)₂], respectively. The reaction products were identified in the reaction mixtures by ³¹P{¹H} and ¹H NMR.