13C NMR study of 3-(X-benzal)phthalides and 2-(X-benzal)-1,3-indanediones

Abstract

13C NMR spectra of 14 derivatives of 3-(X-benzal)phthalides (I) and 10 derivatives of 2-(X-benzal)-1,3-indanediones (II) were investigated. The correlation of 13C chemical shifts of carbon atoms of the phthalide ring with σ-constants showed that the electronic effect of substituents was transmitted from the benzylidene group of 3-(X-benzal)phthalides on the chemical shift of the carbonyl group not only through oxygen, but also through the aromatic ring of the phthalide moiety. The transmission of substituent effects in 2-(X-benzal)-1,3-indanediones on the chemical shift of the carbonyl groups was more pronounced on the carbonyl, which is in the trans-arrangement with respect to the aryl group. This phenomenon was also observed at carbon atoms of the benzene ring of the indanedione moiety closer to the trans-CO group.