Chloride ion pairs as catalysts for the alkylation of aldehydes and ketones with C-H acidic compounds

Chloride anions associated with various soft cations (like tetraalkyl ammoniums, alkyl imidazoliums or pyridiniums) were shown to be able to promote the alkylation of carbonyl derivatives with acidic compounds, as exemplified on Knoevenagel and aldol condensations under relatively mild conditions. This activity was attributed to an enhanced nucleophilicity of the chlorine anion, originating from a softness/hardness mismatch between the anion and the cation.     

Electronic and Steric Ligand Effects in the Radical Polymerization of Vinyl Acetate Mediated by β‐Ketoiminate Complexes of Cobalt(II)

Complexes Co[OC(Ph)CHC(Me)NAr]₂ [Ar=Ph, 1 ; o,o′‐C₆H₃Me₂ (Xyl), 2 ; p‐C₆H₄CF₃, 3 ] are tested in the polymerization of vinyl acetate (VAc) initiated by V‐70 (0.8 equiv) at 30 °C. Polymerization occurs without any notable induction time yielding PVAc with relatively low polydispersity, but with higher than expected M_n values, which indicates inefficient trapping processes. The apparent polymerization rate constant varies in the order 2 > 1 > 3 . Controlled polymer growth is also observed when the polymerization is conducted in the presence of a much higher V‐70/ 1 ratio, demonstrating that this system can also function as a transfer agent in a degenerative transfer process. Competition between chain growth and catalyzed chain transfer (CCT) is also observed, the latter prevailing at higher temperatures. Comparison of these results with previous reports on bis(β‐diketonato) complexes allows a separate assessment of ligand electronic and steric effects in the ability to control polymerization.     

Bases of rearrangement invariant spaces

We prove that if E is a rearrangement-invariant space, then a boundedly complete basis exists in E, if and only if one of the following conditions holds: 1) E is maximal and E ≠ L ₁[0, 1]; 2) a certain (any) orthonormal system of functions from L _∞[0, 1], possessing the properties of the Schauder basis for the space of continuous on [0, 1] functions with the norm L _∞, represents a boundedly complete basis in E. As a corollary, we state the following assertion: Any (certain) orthonormal system of functions from L _∞[0, 1], possessing the properties of the Schauder basis for the space of continuous on [0, 1] functions with the norm L _∞, represents a spanning basis in a separable rearrangement-invariant space E, if and only if the adjoint space E* is separable. We prove that in any separable rearrangement-invariant space E the Haar system either forms an unconditional basis, or a strongly conditional one. The Haar system represents a strongly conditional basis in a separable rearrangement-invariant space, if and only if at least one of the Boyd indices of this space is trivial.     

Infrared Spectra and Transmission of Substituent Effects Through the Arylazomethine Group in Aromatic Schiff Bases

The IR frequencies and integrated intensities of the nitrile group of two series of aromatic Schiff bases have been measured. The data obtained are compared with the Hammett σ constants as well as with the calculated dipole moment derivatives of the nitrile group. An evaluation of the transmission coefficient Π of the arylazomethine group is reported.     

Oligo(borolyl)benzenes—Synthesis and Properties

Herein, we report the synthesis of boroles that are linked by a conjugated phenylene spacer. The characterization of these compounds was completed by NMR and UV/Vis spectroscopy, as well as X‐ray crystal diffraction. Furthermore, the coordination behavior of these oligoboroles towards five electronically and sterically disparate pyridine derivatives was studied and revealed fundamental differences in the properties of the resulting adducts. The experimental results were supported by density functional theory (DFT) calculations that showed a charge‐transfer effect upon formation of the pyridine‐4‐carbonitrile adduct. By chemical reduction of a tris(borolyl)‐substituted benzene derivative, a hexaanion was isolated as a result of a two‐electron reduction of each borolyl moiety. The interaction of the borolyl units through the aryl spacer, and the possible increase of the Lewis acidity due to the conjugation of the borolyl moieties, were investigated by base transfer reactions.     

一维和二维多势阱能谱的Bsplines计算

用Bsplines函数基计算了一维多势阱和二维Henon Heiles势的能谱,得到了精度较高的结果.将这一结果与采用高斯基函数计算的结果进行比较,结果表明:Bsplines函数基用于研究一维束缚态问题比高斯函数基方法更方便,具有灵活、可塑性强、效率高等优点,适用于不同形式势作用下的系统的变分求解.