期刊
TETRAHEDRON
卷 61, 期 36, 页码 8616-8624出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.tet.2005.07.001
关键词
7,7-bis(heteroazulen-3-yl)-8,8-dicyano-1,4-quinodimethanes; heteroazulene; redox potential; conformational change
The synthesis and properties of a novel type of 5-[bis(1-heteroazulen-3-yl)methylidene]pyrimidine-2,4,6(1,3,5 H)-triones(13a-c) and (14a-c) are studied. The synthetic procedure is based on addition of bis(1-heteroazulen-3-yl)methyl cations with barbituric acid and subsequent oxidation by o-chloranil. Structural characteristics of 13a-c and 14a-c were clarified on inspection of the C-13 NMR spectral data and X-ray crystal analysis. Based on the investigation of the UV-vis spectra of 13a-c and 14a-c and their protonated cations, conformational change of the heteroazulene-moiety and the barbituric acid-moiety is suggested. In the CV measurements of 13a-c and 14a-c, two reversible reduction waves are observed, indicating the stabilizing ability of heteroazulenes toward the corresponding radical and anion species. Furthermore, 13a-c and 14a-c exhibit one irreversible oxidation wave and the corresponding reduction wave appearing in a far negative region, which suggested a conformational change in the radical cation during the redox process. The conformational change is rationalized on the basis of the MO calculations. (c) 2005 Elsevier Ltd. All rights reserved.
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