Tertiary amine effect: synthesis of some novel spirosubstituted pyrido[2,3-d]pyrimidines

5-Formyl-6-tertiaryamino uracils 3 prepared from 6-chloro-5-formyl uracil derivative 1 react with barbituric acids 4 in the presence of base catalyst to afford a novel class of spirosubstituted pyrido[2,3-d]pyrimidines 5 via 1,6-electro-cyclisation in excellent yields.     

A Versatile Methodology for the Synthesis of α,β‐Unsaturated 3‐Iminophosphines

Phorteen phine phosphines : Fourteen new α,β‐unsaturated β‐chloroimines were synthesized from inexpensive ketones by using the Vilsmeier–Haack reagent followed by Schiff‐base condensation. Each imine was subsequently converted to an α,β‐unsaturated 3‐iminophosphine through either late‐metal‐catalyzed phosphorus–carbon cross‐coupling or through an addition–elimination sequence (see scheme). This high‐yield protocol serves as a general means to produce α,β‐unsaturated 3‐iminophosphines.

     

Modeling long-term creep rupture by debonding in unidirectional fibre-reinforced composites

Delayed fracture due to debonding can be observed in many unidirectional fibre-reinforced composites when the fibre/matrix interface experiences creep. The aim of this work is to describe such a phenomenon within the recently proposed modeling framework of transverse isotropy that allows for a neat decomposition of the mechanical behavior into fibre-directional, transverse, and pure shear parts. Specifically, debonding is here chosen to be governed by the tension transverse to the fibres. One can then speak of a mode-I debonding if use is made of the terminology adopted in fracture mechanics. On another hand, the time-dependent response is attributed to the matrix constituent. As the role of this latter is to deform and support stresses primarily in shear, a viscoelastic behavior is introduced that affects solely the pure shear part of the behavior. We show that both characteristics can be easily embedded into the aforementioned formulation. Among others, the occurrence of tertiary creep is made possible to predict. It is otherwise found that the predicted debonding path always propagates along the direction of the fibres in agreement with many experimental observations found in the literature. On the numerical side, the algorithmic treatment of debonding is independent of the one for viscoelasticity. This renders the implementation within the context of the finite element method very easy.     

Ru(II) COMPLEXES CONTAINING CHELATING PHOSPHINE LIGANDS. SYNTHESIS,CHARACTERIZATION, AND X-RAY CRYSTAL STRUCTURES OF DICHLOROBIS(1,2-BIS(DIPHENYLPHOSPHINO)ETHANE)Ru(II) AND THE COORDINATIVELY UNSATURATED TRIGONAL-BIPYRAMIDAL CATION,CHLOROBIS-(1,2-BIS(DIPHENYLPHOSPHINO)ETHANE)Ru(II)

Abstract

The reaction of trans-RuCl₂(dppe)₂ (1), with AgBF₄ in tetrahydrofuran leads to abstraction of one of the halide ligands to produce the trigonal-bipyrimidal complex, [RuCl(dppe)₂]BF₄ (2). Both products are characterized by ³¹P NMR spectroscopy and their crystal structures determined. For the coordinatively unsaturated trigonal-bipyramidal complex (2), we found no evidence for the presence of more than one species or fluxional behaviour at room temperature in the ³¹P NMR spectrum. This complex was found to possess a trigonal-bipyramidal geometry in the solid state. Crystals of 1 are monoclinic, space group P2₁/c with a = 23.713(4)Å, b=11.156(1)Å, c = 17.595(2)Å, β=103.23(1) and v=4531(1)ų. Convergence to conventional R values of R=0.043 and R_w = 0.042 was obtained for 416 variable parameters and 2746 reflections with I>3σ(I). Compound 2 in triclinic, P1, a=12.482(3)Å, b=12.543(3)Å, c=17.582(3)Å, α = 87.52(2)°, β= 72.70(2)° γ = 74.35(2)° and V= 2529(1)ų. Values of R = 0.072 and R_w = 0.097 were obtained for 487 variable parameters and 3242 reflections with I>3σ(I)     

叔胺弱碱树脂的强度研究

研究了影响苯乙烯系叔胺弱碱性阴离子交换树脂性能的诸因素．提出了经二甲胺胺化 后所形成的胺基桥是影响树脂强度的主要原因的观点．用磷酸一渗磨圆球率方法对树脂进行强 度检验,使强度数据更为可靠．     

Mechanistic Study of the Role of Primary Amines in Precursor Conversions to Semiconductor Nanocrystals at Low Temperature

Primary alkyl amines (RNH₂) have been empirically used to engineer various colloidal semiconductor nanocrystals (NCs). Here, we present a general mechanism in which the amine acts as a hydrogen/proton donor in the precursor conversion to nanocrystals at low temperature, which was assisted by the presence of a secondary phosphine. Our findings introduce the strategy of using a secondary phosphine together with a primary amine as new routes to prepare high‐quality NCs at low reaction temperatures but with high particle yields and reproducibility and thus, potentially, low production costs.     

Catalyst-free alkanoylation of aromatic rings via arylstannanes. Scope and limitations

The reaction of alkanoyl chlorides with arylstannanes in 1,2-dichlorobenzene (180 °C) is a simple and direct route for the catalyst-free and regioselective synthesis of tertiary alkyl aryl ketones in good to excellent isolated yields (55-77%). Nevertheless, under similar conditions, reactions carried out with alkanoyl chlorides bearing α-hydrogens render only the product of protodestannylation.     

Upconversion in Er3+-doped Bi2O3-Li2O-BaO-PbO tertiary glass

Radiative properties of Er3+-doped tertiary bismuth glass has been analyzed by the Judd-Ofelt theory. NIR to visible upconversion in the Er3+-doped glass has been reported. The mechanism for the upconversion is explained on the basis of quadratic dependence on excitation power and on the energy-matching scheme. Energy transfer is noted as the dominant process including the long-lived 4I11/2 level as the intermediate state for the green and red upconversion emissions. The effect of temperature on the fluorescence intensity of the two bands due to 2H11/2-->4I15/2 and 4S3/2-->4I15/2 transitions as well as on the transitions due to Stark components of the 4S3/2 level have been monitored and it is concluded that their intensity ratio may serve as better temperature sensing device.