Carbon-13 chemical shifts of alkene carbons in 2-acylidene-3,5-diaryl-2,3-dihydro-1,3,4-thiadazoles and related benzothiazoles and -selenazoles, and their relationship to other push-pull alkenes

被引:20
作者
Mueller, JL [1 ]
Gibson, MS [1 ]
Hartman, JS [1 ]
机构
[1] BROCK UNIV,DEPT CHEM,ST CATHARINES,ON L2S 3A1,CANADA
来源
CANADIAN JOURNAL OF CHEMISTRY-REVUE CANADIENNE DE CHIMIE | 1996年 / 74卷 / 07期
关键词
carbon-13; NMR; chemical shifts; push-pull olefins; 1,3,4-thiadiazoles; benzothiazoles; benzoselenazoles;
D O I
10.1139/v96-148
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Carbon-13 chemical shifts of alkene carbons are observed in the ranges 78-109 ppm (C alpha) and 154-164 ppm (C beta) for a series of 11 2-acylidene-3,5-diaryl-2,3-dihydro-1,3,4-thiadiazoles, 3 2-acylidene-3-alkyl-2,3-dihydrobenzothiazoles, and 2 2-acylidene-3-alkyl-2,3-dihydrobenzoselenazoles of known geometry, indicating appreciable charge polarization in these compounds as in other push-pull olefins. Substitution that promotes more extensive charge delocalization results in the C alpha signal shifting to the higher-frequency end of the chemical shift range. The observed shifts are compared with those calculated according to the Pretsch scheme.
引用
收藏
页码:1329 / 1334
页数:6
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