Synthesis of polysubstituted pyridines under combined microwave and ultrasound irradiation: K2CO3-promoted tandem addition/cyclization/hydrogen shift process
作者:Huangdi Feng、Yuan Li、Erik V. Van der Eycken、Yanqing Peng、Gonghua Song
DOI:10.1016/j.tetlet.2011.12.103
日期:2012.2
A convenient and efficient K2CO3-promoted tandem reaction of chalcone, malononitrile, and methanol for the synthesis of highly functionalized pyridines has been developed. This multi-component reaction employing the weak nucleophilic agent methanol proceeded smoothly under combined microwave and ultrasound irradiation (CMUI). The reaction mechanism was proposed to consist of a Michael addition. a methoxylation of C N bond, a cyclization to a 1,4-dihydropyridine and an intermolecular hydrogen shift between 1,4-dihydropyridine and initial chalcone. (C) 2011 Elsevier Ltd. All rights reserved.
New diphenylamine-based donor–acceptor-type conjugated polymers as potential photonic materials
A new series of donor-acceptor-type conjugated polymers (P1 and P2) carrying a diphenyl amine moiety were synthesized via Wittig condensation technique. The polymers structures were well established by FT-IR, H-1 NMR, elemental analysis and gel permeation chromatographic techniques. They exhibited good thermal stability with an onset decomposition temperature of approximately 325 degrees C under nitrogen atmosphere. The optical and electrochemical properties of the polymers were studied by UV-vis, fluorescence emission spectroscopy and cyclic voltammetry. They exhibited good fluorescence in dilute solutions and showed solvatochromic behavior in various polar solvents. The electrochemical studies revealed that the polymers possess low-lying LUMO energy levels that ranging from -3.47 to -3.73 eV and high-lying HOMO energy levels that ranging from -5.57 to -5.81 eV. The thirdorder nonlinear optical properties of the polymers were investigated using the Z-scan technique. The effective two-photon absorption (TPA) coefficients (beta) of the polymers were found to be 0.645 x 10(-10) and 0.212 x 10(-10) m/W. (C) 2011 Elsevier Ltd. All rights reserved.