Substituent effects in various alkyl derivatives of 9aH-quinolizine-1,2,3,4-tetra-carboxylate studied by<sup>13</sup>C NMR spectroscopy and X-ray analysis
作者:Krystyna Kamieńska-Trela、Lidia Kania、Zpfia Lipkowska、Elżbieta Bednarek、William T. Raynes
DOI:10.1039/p29900000625
日期:——
The 13C NMR spectra of 22 alkyl-substituted 9aH-quinolizine-1,2,3,4-tetracarboxylates have been obtained and X-ray analyses have been performed for three of them. The chemical shift differences between the parent 9aH-quinolizine and the methyl-substituted compounds can only be interpreted in terms of the usual α and β effects for 8-methyl-9aH-quinolizine. 6-, 7-, 9-, and 9a-methyl substituents cause
已获得22个烷基取代的9a H-喹啉-1,2,3,4-四羧酸酯的13 C NMR光谱,并对其中的三个进行了X射线分析。母体9a H-喹啉嗪与甲基取代的化合物之间的化学位移差异只能根据8-甲基-9a H-喹啉嗪的通常α和β效应来解释。6-,7-,9-和9a-甲基取代基不仅会导致取代位置的碳非常大的去屏蔽以及相邻原子处的屏蔽变化,而且还会影响两个碳原子上的其他碳的屏蔽正在研究的化合物。观察到的变化用环的甲基之间的位阻解释B和环A的酯基,以及由甲基引入的超共轭作用。