多羰基甾酮的选择性还原反应研究

在不同金属离子存在下,多羰基甾酮的甾核及支链上都发生了羰基与硼氢化钠的还原反应,得到具有不同的区域选择性和立体选择性的还原产物.     

Asymmetric reduction of acetophenone and propiophenone by NaAl(IPTOLate)H2 combined with enantiomeric enrichment of the reaction product as an inclusion complex with IPTOL

An improved procedure was developed for asymmetric reduction of acetophenone and propiophenone by the chiral reagent NaAl(IPTOLate)H₂. This procedure is based on isolation of the chiral alcohol that formed as a crystalline host—guest complex with the IPTOL ligand. The enantiomeric enrichment of the product was as high as 97% ee. The ability of IPTOL and its analogs to form host—guest complexes with a number of ether-type solvents, 1-phenylethanol, and 1-phenylpropan-1-ol as well as thermal stabilities of IPTOL-containing complexes with these alcohols were studied.     

Effect of 4f-shell excitation of Eu(fod)3 on its complex formation with alicyclic ketones

The complex formation of alicyclic ketones, viz., camphor, cyclohexanone, menthone, and cytisine, with the Eu(fod)₃ chelate (fod is 7,7-dimethyl-1,1,1,2,2,3,3-heptafluorooctane-4,5-dione) in the ground and excited states was studied by chemiluminescence and kinetic luminescence spectroscopy, respectively. The stability constants and thermodynamic parameters of complex formation were determined. An increase in the stability of the electron-excited complexes [Eu(fod)₃*·Ketone] is explained by the enhancement of the acceptor ability of the Eu³⁺ chelate due to an increase in the fraction of the covalent component caused by the involvement of 4f-orbitals. The results obtained give direct evidence for the effect of the 4f-shell excitation of Eu(fod)₃ on complex formation due to the involvement of f-electrons in the chemical bonds.     

KF/clinoptilolite nanoparticles as a novel catalyst for the green synthesis of chromens using three component reactions of 4‐hydroxycoumarins: Study of antioxidant activity

In this research, the green synthesis of chromen derivatives in good yields is described via three‐component reactions of 4‐hydroxycumarine, aldehydes or ketones, and methyl ketones in the presence of KF/clinoptilolite nanoparticles (KF/CP‐NPs) under solvent‐free conditions at 50°C in low time. The present methodology suggests some advantages such as low reaction time, easy and simple procedure, green method, inexpensive catalyst, high yield of product, and existence of different substrates for performing these reactions. In addition, it should be mentioned that antioxidant activity was studied for some prepared compounds, such as 4a–4d, by DPPH radical trapping and reducing potential tests of ferric ion and then comparing results with TBHQ and BHT as synthetic antioxidants. In this study, compounds 4c was shown to have moderate DPPH radical trapping, and compounds 4b and 4d displayed good reducing power of ferric ion.     

Kinetic study of nucleophilic reactivity of heterocyclic amines with 4,6-dinitrobenzofuroxan in acetonitrile

The reaction kinetics of 4,6-dinitrobenzofuroxan with five heterocyclic amines was investigated spectrophotometrically (UV–Vis) in acetonitrile at 20 °C. It was observed that the rate constants of these reactions increased as follows: 2-aminopyrimidine > 2-aminothiazole > 2-aminobenzothiazole > 5-amino-3,4-dimethylisoxazole > 2-amino-5-trifluoromethyl-1,3,4-thiadiazole. Further, second-order rate constants (k₁) pertaining to the C–N and C–C bond forming step of these complexation processes fit to the three parameter equation log k (20 °C) = s_N (N + E), allowing the determination of the nucleophilicity parameters (N) of the five heterocyclic amines. The heterocyclic amines were subsequently ranked on the comprehensive nucleophilicity scale defined by Mayr et al. (2003), providing a direct comparison of n-, π-, and σ-nucleophiles.     

Studies on 3,5-diaminopyrazole derivatives

The behaviour of 3,5-diamino-4-phenylazopyrazole toward a variety of reagents is reported. Several new 3,5-diaminopyrazole derivatives as well as amino derivatives of fused pyrazoles have been prepared.

---

Untersuchungen an 3,5-Diaminopyrazol-Derivaten

Zusammenfassung Es wird über das Verhalten von 3,5-Diamino-4-phenylazopyrazol gegenüber verschiedenen Agentien berichtet. Es wurden sowohl einige neue 3,5-Diaminooyrazol-Derivate als auch einige Aminoderivate von kondensierten Pyrazolen dargestellt.

     

On the mechanism for the photooxidation of aromatic azides containing a secondary N–H bond: A sequence of intramolecular transformations with the formation of heterocyclic oximes

During the photooxidation of aromatic azides containing a secondary N–H bond at the para-position, a sequence of intramolecular transformations of nitroso oxides led to the formation of heterocyclic oximes along with the corresponding nitroso and nitro compounds.     

Synthesis of alkyl (α-phenylthioalkenyl) ketones containing a (Z)-trisubstituted olefinic fragment

Warren"s method, which has been proposed for the synthesis of -phenylthiodialkyl ketones, appeared to be inefficient for the preparation of their alkenyl alkyl analogs. The latter were prepared in good yields by alkenylation of alkyl phenylthiomethyl ketones with alkenyl bromides.     

Enzymatic synthesis of optically active α-chloro-δ-hydroxy-β-ketoalkanephosphonates and reactions thereof

A novel and enzymatic approach to α-chloro-δ-hydroxy-β-ketoalkanephosphonates was developed via enantioselective CALB-catalyzed acetylation and CRL-catalyzed hydrolysis. The resultant optically active compounds provide, via Horner-Wadsworth-Emmons (HWE) reaction, chiral α,β-unsaturated ketones that are building block with potential application in organic synthesis.