APPLICATION OF C-13 NMR-SPECTROSCOPY TO CONFORMATIONAL-ANALYSIS ABOUT THE N-C(PHENYL) BOND

C-13 NMR spectra of some alpha, beta-(9,10-dihydroanthracene-9,10-diyl)-N-arylsuccinimides (1) have been reported. The 2'-substituted derivatives (1b, d, f) exhibit duplexicity in 1', 2', 6' and alpha, beta-carbon resonances and demonstrate the presence of two non-planar conformations about the N - C (phenyl) bond. Anisotropic interaction and the steric compression of the cage-benzo ring have been quite effective and diagnostic in conformational analysis about the N - C bond. In the case of 2'-methyl substituent, the energy barriers, DELTA-G not-equal for the two conformers have been evaluated to be 23.6 and 23.0 kcal/mole. Under conditions when 2'- and 6'-substituents do not contain protons, C-13 NMR may provide evidence for the non-planar conformations about the N - C (phenyl) bond by exhibiting different C-13 resonances for 2'- and 6'-carbons.