Aziridine Ring Opening as Regio- and Stereoselective Access to C-Glycosyl-Aminoethyl Sulfide Derivatives

A short synthetic route to stereoselective access to C-glycosyl-aminoethyl sulfide derivatives has been developed through the reaction of tributhyltin derivatives of glycals with aziridinecarboaldehyde and the regioselective ring opening of a chiral aziridine with thiophenol. The absolute configurations of the resulting diastereoisomers were determined by 1H NMR spectroscopy.     

一种新型吡啶鎓盐的合成、结构及光学性质

通过吡啶盐与3，4-二甲氧基苯甲醛在甲醇中反应，得到了一种新型的化合物，即4-[（3"，4"-二甲氧基)苯乙烯基]-N-甲基吡啶高氯酸盐，分子式为C16H18ClNO6。化合物的结构通过红外、元素分析、氢谱、电喷雾质谱和X-单晶衍射仪进行分析与表征。结果表明：该化合物属正交晶系，空间群Pbca，晶胞参数a = 13.5897(11) nm, b = 13.9126(11) nm, c = 17.3485(14) nm, α = 90 °, β = 90 °, γ = 90 °, Mr = 355.76, V = 3280.0(5) nm3, Z = 8, F(000) = 1488, Dc = 1.181 g/cm3, μ = 0.265 mm?1。而且还研究了该化合物的光学性质。     

一种具有双光子活性的新型吡啶盐的合成、表征及性质

一种具有双光子活性的新型吡啶盐的合成、表征及性质;D-π-A吡啶盐; 三阶非线性光学特性; 单晶X射线衍射; Z扫描     

Synthesis, Characterization and Two-Photon Absorption Properties of a Novel Pyridinium Salt

A novel pyridinium salt, 2,4-bis[p-(N,N-dimethylamino)styryll-N-metlayl pyridinium iodide (BMSPI) was synthesized and characterized by TG, ^1H NMR spectroscopy and elemental analysis, and the reaction process was studied by using ES-MS. When BMSPI was pumped by a pulsed 1064 nm, 50 ps laser beam, it manifests highly efficient TPA (Two-Photon Absorption) and up-conversion superradiance. The up-conversion efficiency was 6.0% at the pump energy of 4-6 mJ and the lifetime of two-photon fluorescence was measured as 59 ps.     

Catalytic,Enantioselective Ring Opening of Aziridines

Cooperative metal centers in a bimetallic catalyst facilitate the highly enantioselective ring opening of meso aziridines 1 with silyl nucleophiles (see scheme; TMS=trimethylsilyl). The 1,2‐azidoamides 2 and 1,2‐amidonitriles 3 obtained in this way in high yields and with up to 99 % ee are valuable precursors to enantiomerically pure 1,2‐diamines and β‐amino acids.

     

Nucleophilic Opening of the Oxirane Ring with Tetraalkylammonium Salt Anions in the Presence of Proton Donors

Russian Journal of Organic Chemistry - The behavior of tetraethylammonium salts in nucleophilic opening of the oxirane ring of epichlorohydrin (ECH) in the system ECH–proton donor–Et4N+...     

Electrochemical Characteristics of a Novel Pyridinium Salt as a Candidate Drug Molecule and Its Interaction with DNA

In this article, for the first time, the electrochemical properties of a novel pyridine derivative, 4‐(2‐(2‐hydroxybenzylidene) hydrazinyl)‐1‐(3‐phenylpropyl) pyridinium bromide (abbreviated as 4‐Pyri), and its interaction with double stranded DNA (dsDNA) was investigated. The interaction between candidate drug molecule (4‐Pyri) and dsDNA was analyzed by examining 4‐Pyri (+0.6 V and +0.8 V) and guanine (+1.0 V) oxidation signal changes with Differential Pulse Voltammetry (DPV) and Cyclic Voltammetry (CV). Electrochemical Impedance Spectroscopy (EIS) was used to show the resistance changes before and after the interaction between 4‐Pyri and dsDNA. We showed that after the interaction with 4‐Pyri, the oxidation currents of guanine decreased dramatically, whereas the intrinsic oxidation currents of 4‐Pyri dramatically increased. 4‐Pyri oxidation current differences before and after the interaction with dsDNA enabled us to determine such interaction separately from guanine oxidation signals. In addition, resistance differences were observed at before and after the interaction with each other that confirmed the possible interaction. In addition, toxicity effect (S%) value, which is an important parameter for electrochemical studies indicated 4‐Pyri's toxicity to dsDNA. Our results demonstrated that 4‐Pyri interacts with dsDNA, and could be used as a potential candidate drug molecule due to its remarkable impact on dsDNA.     

Asymmetric Ring Opening in a Tetrazine-Based Ligand Affords a Tetranuclear Opto-Magnetic Ytterbium Complex

We report the formation of a tetranuclear lanthanide cluster, [Yb₄(bpzch)₂(fod)₁₀] ( 1 ), which occurs from a serendipitous ring opening of the functionalised tetrazine bridging ligand, bpztz (3,6-dipyrazin-2-yl-1,2,4,5-tetrazine) upon reacting with Yb(fod)₃ (fod⁻=6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octandionate). Compound 1 was structurally elucidated via single-crystal X-ray crystallography and subsequently magnetically and spectroscopically characterised to analyse its magnetisation dynamics and its luminescence behaviour. Computational studies validate the observed M_J energy levels attained by spectroscopy and provides a clearer picture of the slow relaxation of the magnetisation dynamics and relaxation pathways. These studies demonstrate that 1 acts as a single-molecule magnet (SMM) under an applied magnetic field in which the relaxation occurs via a combination of Raman, direct, and quantum tunnelling processes, a behaviour further rationalised analysing the luminescent properties. This marks the first lanthanide-containing molecule that forms by means of an asymmetric tetrazine decomposition.     

Catalytic Borylative Opening of Propargyl Cyclopropane,Epoxide, Aziridine,and Oxetane Substrates: Ligand Controlled Synthesis of Allenyl Boronates and Alkenyl Diboronates

A new copper‐catalyzed reaction for the stereo‐ and regioselective synthesis of alkenyl diboronates and allenyl boronates is presented. In this process propargyl derivatives of strained three/four‐membered rings were employed as substrates and B₂pin₂ was used as the boronate source. Selective formation of the alkenyl diboronate versus the allenyl boronate products was controlled by the choice of phosphine ligand.     

Fluorine as a Regiocontrol Element in the Ring Opening of Bicyclic Aziridiniums

The origin of the variation in the regioselectivity of the nucleophilic ring opening of a series of bicyclic aziridinium ions derived from N‐alkylprolinols was investigated by quantum‐chemical computations (M06‐2X/6‐31+G(d,p)‐SMD). These aziridiniums differ only in the degree and the configurations of F‐substitution at C(4). With the azide ion as nucleophile, the ratio of the piperidine to the pyrrolidine product was computed. An electrostatic gauche effect influences the conformation of the adjoining five‐membered ring in the fluorinated bicyclic aziridinium. This controls the regioselectivity of the aziridinium ring opening.     

Brook Rearrangement as a Trigger for the Ring Opening of Strained Carbocycles

The combined regio‐ and stereoselective carbometalation of cyclopropenyl amides, followed by the addition of an acyl silane, led to the formation of polysubstituted cyclopropyl derivatives as unique diastereoisomers. Upon warming of the reaction mixture to room temperature, a Brook rearrangement proceeded with inversion of configuration to provide ready access to δ‐ketoamides possessing a quaternary carbon center with high enantiomeric ratios through selective C? C bond cleavage of the ring.     

Formal Cycloadditions Driven by the Homolytic Opening of Strained,Saturated Ring Systems

The field of strain-driven, radical formal cycloadditions is experiencing a surge in activity motivated by a renaissance in free radical chemistry and growing demand for sp³-rich ring systems. The former has been driven in large part by the rise of photoredox catalysis, and the latter by adoption of the “Escape from Flatland” concept in medicinal chemistry. In the years since these broader trends emerged, dozens of formal cycloadditions, including catalytic, asymmetric variants, have been developed that operate via radical mechanisms. While cyclopropanes have been studied most extensively, a variety of strained ring systems are amenable to the design of analogous reactions. Many of these processes generate lucrative, functionally decorated sp³-rich ring systems that are difficult to access by other means. Herein, we summarize recent efforts in this area and analyze the state of the field.     

Experimental and Theoretical Investigations into the Paratropic Ring Current of a Porphyrin Sheet

Anomalous induced magnetic effects were observed in a directly fused square‐planar porphyrin sheet 1 , in that the protons above the center of the tetraporphyrin core were characteristically shifted downfield in the ¹H NMR spectrum. These observations suggest a rare paratropic ring‐current effect around the planar cyclooctatetraene (COT) core of 1 . To examine the spatial distribution of the induced magnetic effect, face‐to‐face dimeric complexes of porphyrin sheet 1 with bipyridyl‐type guest molecules ( G1 – G3 ) were prepared, which provided complexation‐induced shifts (CISs) of the guest molecules as a neat experimental guide to the distance dependence of the induced magnetic effects in 1 . Nucleus‐independent chemical shift (NICS) values of 1 were calculated by varying the distance of the probe from the plane of 1 . Whereas a simple bell‐type profile was estimated for the complex ( 1 )₂–( G1 )₄, the distance profiles of the CIS became increasingly flat for ( 1 )₂–( G2 )₄ and ( 1 )₂–( G3 )₄. Finally, we investigated the paratropic ring‐current effect just above the COT core of the complex 1 –( G4 )₂, which agrees well with the theoretically estimated distance‐dependent induced magnetic effect. Consequently, both experimental and theoretical studies on the complexes of porphyrin sheets with guest molecules revealed for the first time a unique distance dependence of the paratropic ring current.     

Ring Opening of Bicyclo[3.1.0]hexan‐2‐ones: A Versatile Synthetic Platform for the Construction of Substituted Benzoates

Described is the development of a highly efficient 2π disrotatory ring‐opening aromatization sequence using bicyclo[3.1.0]hexan‐2‐ones. This unprecedented transformation efficiently proceeds under thermal conditions and allows facile construction of uniquely substituted and polyfunctionalized benzoates. In the presence of either amines or alcohols formation of substituted anilines or ethers, respectively, is achieved. Additionally, the utility of this method was demonstrated in a short synthesis of sekikaic acid methyl ester.