13C NMR Studies on 3-Aryl-4-Cyanosydnones (II). NMR Spectroscopy and the Chain-Conjugated Structure of Sydnones |
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Authors: | S P Wang C N Kuo S Ma M-Y Yeh |
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Institution: | Department of Chemistry , National Cheng Kung University Tainan , Taiwan, 70101, R.O.C. |
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Abstract: | Carbon-13 NMR spectra of 3-aryl-4-cyanosydnones have been analyzed to serve as an electronic structure probe of sydnones. 2-Dimensional INADEQUATE experiments and spin-lattice relaxation time measurements were employed to ascertain exact assignments. Deshielding of the phenyl carbon para to the sydnone ring manifests that N(3) bears positive charge. The electronic-rich property of C(4) is confirmed by shift data of cyano carbons, which have been found by far the most shielded cyano carbons in nitrile-containing compounds yet reported. Shift variations of C(5) resulting from the substitution at C(4) and supplementary oxygen-17 chemical shift data provide evidence in favor of the chain-conjugated structure. |
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Keywords: | 3-Aryl-4-cyanosydnones 13C NMR Chemical Shift Anisotropy Relaxation |
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