A versatile palladium catalyst system for Suzuki-Miyaura coupling of alkenyl tosylates and mesylates

A general and effective palladium system for Suzuki-Miyaura coupling of alkenyl electrophiles under mild reaction conditions is reported. With the Pd(OAc)(2)/CM-phos system, a variety of alkenyl tosylates are coupled well with ArB(OH)(2). Moreover, the first successful examples of using alkenyl mesylates in alkenylation are also described.     

Gold(I)‐Catalyzed Enantioselective Intermolecular Hydroarylation of Allenes with Indoles and Reaction Mechanism by Density Functional Theory Calculations

Chiral binuclear gold(I) phosphine complexes catalyze enantioselective intermolecular hydroarylation of allenes with indoles in high product yields (up to 90 %) and with moderate enantioselectivities (up to 63 % ee). Among the gold(I) complexes examined, better ee values were obtained with binuclear gold(I) complexes, which displayed intramolecular Au^I Au^I interactions. The binuclear gold(I) complex 4c [(AuCl)₂( L3 )] with chiral biaryl phosphine ligand (S)‐(−)‐MeO‐biphep ( L3 ) is the most efficient catalyst and gives the best ee value of up to 63 %. Substituents on the allene reactants have a slight effect on the enantioselectivity of the reaction. Electron‐withdrawing groups on the indole substrates decrease the enantioselectivity of the reaction. The relative reaction rates of the hydroarylation of 4‐X‐substituted 1,3‐diarylallenes with N‐methylindole in the presence of catalyst 4c [(AuCl)₂( L3 )] / AgOTf [ L3 =(S)‐(−)‐MeO‐biphep], determined through competition experiments, correlate (r²=0.996) with the substituent constants σ. The slope value is −2.30, revealing both the build‐up of positive charge at the allene and electrophilic nature of the reactive Au^I species. Two plausible reaction pathways were investigated by density functional theory calculations, one pathway involving intermolecular nucleophilic addition of free indole to aurated allene intermediate and another pathway involving intramolecular nucleophilic addition of aurated indole to allene via diaurated intermediate E2 . Calculated results revealed that the reaction likely proceeds via the first pathway with a lower activation energy. The role of Au^I Au^I interactions in affecting the enantioselectivity is discussed.     

Long-Period Gratings in Planar Optical Waveguides

Our progress in the study of long-period gratings (LPGs) in planar optical waveguides is reviewed. In particular,experimental LPGs in glass and polymer waveguides are presented to demonstrate the potential of LPG-based waveguide devices.     

关于3连通图的容错直径和宽直径

容错直径和宽直径是度量网络可靠性和有效性的重要参数．对任意k连通图，它的容错直径Dk不超过宽直径dk,本证明：当D2=2时，d3≤max{D， l，2D3-2}；当D2≥3时，d3≤(D2-1)[2(D2-1)(D3-1)-D2-2] 1．     

Design and analysis of coplanar waveguide optical modulator using finite element method

An analysis is given on the finite element method (FEM) for calculating the various parameters of optical modulators and a computer program is written to solve the finite element equation. Based on this method, a Mach-Zehnder type electro-optic modulator with coplanar waveguide (CPW) electrode is designed and fabricated. When compared with the Fourier series method, small differences on the 3-dB bandwidth, characteristic impedance and half-wave voltage, etc. are obtained.     

Mg-Benzophenonketyl als Initiator für die anionische Polymerisation von Methylmethacrylat

Ohne Zusammenfassung     

New synthetic protocols for the preparation of unsymmetrical bisindoles

Novel unsymmetrical bisindoles were synthesized by a solvent-free C-C bond-formation reaction under mild conditions. Starting from aziridines or hydroxyl precursors, indoles have been used as C-nucleophiles to form new pharmacologically interesting bisindoles via an electrophilic aromatic substitution pathway in good to excellent yields. [reaction: see text]