Control of the rotational barrier and spatial disposition of the N-(2′-methylphenyl) group in succinimides by substituent and solvent effects

Both the rotational barrier for the N-(2′-methylphenyl) group in benzylamino-N-(2′-methylphenyl)succinimides 1a–h (X = NEt2, OMe, Me, H, F, Cl, CO2Me and NO2) and the spatial disposition of the N-(2′-methylphenyl) group in N-(4′-substituted 2′ -methylphenyl)-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboximides 2a–h (X = NEt2, OMe, Me, H, F, Cl, CO2Me and NO2) are controlled by the substituents present and the solvents used. The rotational barrier of 1 decreases with an increase in σp (Hammett’s para substituent constant of X) and increases in proportion to an increase of the solvent parameter [ET(30)]. Clear correlation was observed in the plots of the syn/anti ratio of 2 against σm (Hammett’s meta-substituent constant of X) and the ratios are also controllable by the solvent polarity (µ).