Collect. Czech. Chem. Commun. 1999, 64, 1709-1726

Multivariate Regression with Substituent Shift Increments. IV. 2-(4-X-Phenyl)-1,3-dihydro-2H-isoindole-1,3-diones and 3-(4-X-Phenyl)-3,4-dihydro-2H-1,3-benzoxazine-2,4-diones

Miroslav Holíka,*, Zdeněk Friedlb, Karel Waisserc and Jiří Gregorc

a Department of Theoretical and Physical Chemistry, Faculty of Science, Masaryk University, CZ-611 37 Brno, Czech Republic
b Faculty of Chemistry, Technical University Brno, CZ-612 00 Brno, Czech Republic
c Department of Inorganic and Organic Chemistry, Pharmaceutical Faculty, Charles University, CZ-501 65 Hradec Králové, Czech Republic


Two series of para disubstituted benzenes were studied: 2-(4-X-phenyl)-1,3-dihydro- 2H-isoindole-1,3-diones (1) and 3-(4-X-phenyl)-3,4-dihydro-2H-1,3-benzoxazine-2,4-diones (2). Their 1H and 13C chemical shifts were correlated with substituent shift increments (SSI) aj and zj, respectively. For 13C chemical shifts, all four zj values, zi, zo, zm, and zp, were used to check the assignment and to find out possible variables for improvement of regression equations. Significant deviations from plain additivity were observed in the case of δH3 and δC3 chemical shifts. This can be explained by changes in diamagnetic anisotropy contribution induced by different twist of 4-substituent from the benzene plane caused by variable substituent in position 1.

Keywords: Substituent shift increments; NMR spectroscopy, 1H and 13C; Substituent effects; Linear regression; Proportionality relationship; Phthalimides; Benzoxazines.