锡促进的烯丙基硒醚和烯丙基硫醚的合成

在金属锡促进下，烯丙基溴与二硒醚或二硫醚反应，生成烯丙基硒醚或烯丙基硫醚 。     

Short-chain polyphosphates: Extraction effects on migration and size estimation of Saccharomyces cerevisiae extracts with polyacrylamide gel electrophoresis

Polyacrylamide gel electrophoresis is commonly used to characterize the chain length of polyphosphates (polyP), more generally called condensed phosphates. After separation, nonradioactive, optical polyP staining is limited to chain lengths greater than 15 ${\mathrm{PO}}_3^{-}$monomers with toluidine blue or 4′,6-diamidino-2-phenylindole. PolyP chain lengths longer than 62${\mathrm{PO}}_3^{-}$monomers were correlated to the shortest DNA ladders. In this study, synthetic linear polyPs (Sigma-Aldrich “Type 45”, estimated mean length of 45 ${\mathrm{PO}}_3^{-}$ monomers), trimetaphosphate (trimetaP: 3 ${\mathrm{PO}}_3^{-}$ ring), tripolyphosphate (tripolyP), pyrophosphate (PP_i), and inorganic orthophosphate (o-P_i) were visualized after separation by an in situ hydrolytic degradation process to o-P_i that was subsequently stained with methyl green. Statistically insignificant migration reduction of synthetic short-chain polyP after perchloric acid or phenol–chloroform extraction was confirmed with the Friedman test. ³¹P diffusion–ordered NMR spectroscopy confirmed that extraction also reduced PP_i diffusivity by <10%. Linear regression between the R_f peak migration value and the logarithm of synthetic polyP molecular weights enabled estimation of extracted polyP chain lengths from 2 to 45 ${\mathrm{PO}}_3^{-}$monomers. Linear polyP extracts from Saccharomyces cerevisiae grown in aerobic conditions were generally shorter than extracts cultured in anaerobic conditions. Extractions from both aerobic and anaerobic S. cerevisiae included tripolyP and o-P_i, but no PP_i.     

Fluoride Ion Receptors: A Comparison of a Polyammonium Monocycle Versus its Bicyclic Corollary

Abstract

Two polyammonium macrocyclic receptors, the monocyclic 3,6,9,17,20,23-hexaazatricyclo [23.3.1.1^11,15]triaconta-1(29), 11,13,15(30),25,27-hexaene (L¹) and its bicyclic analog 1,4,12,15,18,26,31,39-octaazapentacyclo[13.13.13.1^6,10. 1^20,24.1^33,37]-tetratetraconta-6,7,9,20(43),21,23,33(42),34,36-nonaene (L²), have been synthesized as their hexatosylate salts. The propensity for binding fluoride ion was examined using both NMR and potentiometric techniques. The fluoride salts of both receptors have been characterized by X-ray crystallographic methods. For the monocycle, the complex crystallized as the mixed fluoride-bifluoride salt, [H₆L¹]⁶⁺ ·4F^? ·2FHF^? ·4H₂O, and the bicycle crystallized as a complex salt, [H₆L²]⁶⁺ ·F^? ·2FHF^? ·1.5SiF₆ ^2? ·7H₂O.     

Reaction of Mercaptoacetate and Halides Containing Activated Methylenes with Thiocarbamoylimidates: A Novel Approach to the Synthesis of Aminothiazole Derivatives

The reaction of N-thiocarbamoylimidates 1 with methyl thioglycolate leads to the formation of 4-arylamino-5-methoxycarbonylthiazoles 2. The condensation of the same imidates 1 on ethyl bromoacetate, benzyl bromide and chloroacetonitrile provides the corresponding 2-arylaminothiazoles 4.      

三级烯酰胺的串联Heck反应——一种反式2,5-二芳基-3-吡咯啉化合物新颖的合成方法

3-吡咯啉化合物不仅是重要的有机合成中间体, 而且其骨架结构广泛存在于具有生物活性的化合物中. 利用五元环三级烯酰胺的串联Heck反应, 实现了反式2,5-双取代-3-吡咯啉化合物简便、快捷的合成. 该方法首次将环状烯酰胺的α-芳基化反应和双键异构化进行了有效的结合, 为2,5-双取代-3-吡咯啉化合物的合成提供了一种全新的合成方法. 得到的3-吡咯啉产物可分别经氧化反应和还原反应方便地转化成吡咯或吡咯烷化合物.     

2D-QSAR Studies on Phenoxybenzoic Acid Derivatives: A Novel Class of 5a-Reductase Inhibitors

The quantitative structure-activity relationship （QSAR） of 14 phenoxybenzoic acid derivatives was studied by ab initio method at the HF/6-31G level using Guassian03 software. The optimized structures together with some characteristic and electric parameters of the title compounds were obtained; some stereo-parameters were calculated by HyperChem software. Stepwise multiple regression and principal component regression methods are adopted to establish multi-parametric models between biological activity and parameters. The results indicated that the lager Ehomo, M, V and LogP, the smaller Etumo and S, and the higher biological activity. A theoretical direction was provided to synthesize some compounds with high activity.     

Metal-Free Hydrosilylation of Ketenes with Silicon Electrophiles: Access to Fully Substituted Aldehyde-Derived Silyl Enol Ethers

Little-explored hydrosilylation of ketenes promoted by main-group catalysts is reported. The boron Lewis acid tris(pentafluorophenyl)borane accelerates the slow uncatalyzed reaction of ketenes and hydrosilanes, thereby providing a convenient access to the new class of β,β-di- and β-monoaryl-substituted aldehyde-derived silyl enol ethers. Yields are moderate to high, and Z configuration is preferred. The corresponding silyl bis-enol ethers are also available when using dihydrosilanes. The related trityl-cation-initiated hydrosilylation involving self-regeneration of silylium ions is far less effective.     

Electrochemistry: A Tool for Characterization of Hybrid Materials Obtained by Non-Hydrolytic Sol-Gel Route and Containing Ferrocene Derivatives

The 1,1-ferrocenediyldichlorosilane 1 was introduced into oxide matrices (SiO₂, TiO₂, Al₂O₃) by non-hydrolytic sol-gel route. In all cases some degradation of the ferrocenyl moiety occurred. The materials were immobilized onto an electrode surface as a composite film with PTFE and their cyclic voltammograms were studied. For each sample a reduction wave around –375 mV was evidenced which was attributed to the reduction of [Fe^III Cl _x ]^{3 – x} species arising from the decomposition of ferrocenyl species during the condensation process.     

Reactivity of Aquadiethylenetriamineplatinum(II) Ion with Disulfide Moiety Cystine: A Kinetic and Mechanistic Approach

Abstract

Substitution reactions of the complex [Pt(dien)H₂O]²⁺ (where dien = diethylentriamine or 1,5-diamino-3-azapentane) with sulfur-containing L-cystine have been studied in a 1.0 × 10^?1 mol dm^?3 aqueous perchlorate medium at various temperatures (298–323 K) and 4.45 ≤ pH ≤ 2.15 using UV-vis spectroscopy. The products obtained have been characterized by their infrared and ¹H NMR datasets at various pH levels and temperatures. From infrared and ¹H NMR data, products have indicated that [Pt(dien)H₂O]²⁺ reacted with L-cystine forming a Pt–S bond at low pH. At high pH, a product complex through the Pt–N bond has been formed. All rate constants have been evaluated from nonlinear double exponential plots. The activation parameters ΔH^# and ΔS^# have been determined using the Eyring equation. The products, S_Ni, and reversible rate constants have been evaluated.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

GRAPHICAL ABSTRACT      

Reactivity of Bridged Pentelidene Complexes with Isonitriles: A New Way to Pentel‐Containing Heterocycles

The reaction of [Cp*E{W(CO)₅}₂] (E=P ( 1 a ), As ( 1 b ); Cp*=1,2,3,4,5‐pentamethylcyclopentadienyl) with isonitriles RNC (R=tBu, cyclohexyl (Cy), nBu) depends on the steric demand of the substituent at the isonitrile as well as on the stoichiometry of the starting materials. With tBuNC only the Lewis acid/base adducts [Cp*E{W(CO)₅}₂(CNtBu)] (E=P ( 2 a ), As ( 2 b )) are formed. The use of Cy and n‐butylisonitrile leads first to the formation of the Lewis acid/base adduct, but only at low temperatures. At ambient temperatures, a rearrangement occurs and bicyclo[3.2.0]heptane derivatives of the type [{C(Me)C(CH₂)C(Me)C(Me)C(Me)}C(NR)‐ E{W(CO)₅}₂] (E=P, As; R=Cy, nBu) ( 3 a‐Cy , 3 b‐Cy , 3 a‐nBu and 3 b‐nBu ) are obtained. The use of a further equivalent of isonitrile results in products revealing two new structural motifs, the four‐membered ring derivatives [C(Cp*)N(R)C(NR)E{W(CO)₅}₂] ( 4 : E=P, As; R=Cy, nBu) and the bicyclic complexes [[{C(Me)C‐ (CH₂)C(Me)C(Me)C(Me)}C(NR)₂‐ E{W(CO)₅}₂] ( 5 : E=As; R=Cy). The reaction pathway depends on the substituent at the isonitrile. By treatment of 1 a with two equivalents of CyNC only a 2H‐1,3‐azaphosphet complex 4 a‐Cy (E=P; R=Cy) is formed. Treatment of 1 b with two equivalents of CyNC exclusively leads to the complex 5 b‐Cy (E=As; R=Cy). Treatment of 1 a with two equivalents of nBuNC results in a mixture of complexes, the 2H‐1,3‐azaphosphet 4 a‐nBu (E=P; R=nBu) and the bicyclic complex 5 a‐nBu (E=P; R=nBu). For the arsenidene complex 1 b a mixture of the 2H‐1,3‐azarsete complex 4 b‐nBu (E=As; R=nBu) and the bicyclic complex 5 b‐nBu (E=P, As; R=Cy, nBu) is obtained. Complex 4 b‐nBu is the first example of a 2H‐1,3‐azarsete complex. All products have been characterized by using mass spectrometry, NMR spectroscopy, and X‐ray diffraction analysis.     

The Phosphoenolpyruvate Phosphorylation: A Self-Organized Mechanism with Implications to Understand the RNA Transformations

In this article, we present a study about the non-enzymatic hydrolysis of phosphoenolpyruvate (PEP) by following the reaction course through ³¹P NMR spectroscopy. We have demonstrated that PEP in water exists mainly as a very stable cyclic pentacoordinate phosphorus compound in equilibrium with other cyclic forms. This explains the PEP stability in water. In contrast, after addition of an alcohol to a PEP aqueous solution, other very unstable cyclic pentacoordinated intermediates are formed, which immediately collapse, giving a feasible phosphorylation of the alcohol. It is known that cyclic pentacoordinated phosphorus intermediates are favored over the corresponding acyclic intermediates by a factor of 10⁶–10⁸, and this preference, found also in this study, might be the “driver mechanism” able to overcome the clutter of abiotic chemistry, thus permitting formation of pre-RNA molecules probably with a “self-organized process.”     

A Novel Domino Reaction: Cyclization of Alkynyl Sulfides by Reaction with IPy2BF4

Formation of polycyclic structures within a few minutes: The intramolecular cyclization of diynes, activated by a benzenesulfenyl substituent, upon reaction with IPy₂BF₄ proceeds as an efficient exo–endo coupling. A subsequent novel Friedel–Crafts-like ring closure provides the product [Eq. (1)]. Thus, intra- and intermolecular cyclizations can be carried out.     

Tin(IV) Tetrachloride Complexes with Bis-(Dialkylamino)phosphoryl Fluoride: A Multinuclear (119Sn, 31P, 19F,and 1H) NMR Characterization in Solution

The two octahedral complexes SnCl₄·2(O)PF(NR₂)₂ (R = Me or Et) were prepared from reaction of SnCl₄ with the ligand (R₂N)₂P(O)F in anhydrous CHCl₃. The new adducts have been characterized by elemental analysis, IR, and multinuclear (¹¹⁹Sn, ³¹P, ¹⁹F, and ¹H) NMR spectroscopy. The NMR data show that the adducts exist in solution as a mixture of cis and trans isomers with markedly different proportions. When compared with previously described hexamethylphosphoramide (HMPA) and trimethylphosphate (TMPA) analogues, our results indicate that the cis isomer is the predominant species in solution. Low temperature ³¹P and ¹¹⁹Sn NMR spectra show that the compounds partially dissociate in dichloromethane.