CH/π Interaction on the Structure of N-Substituted-4-phenyltetrahydroisoquinoline Derivatives

Rotational barriers about the C-N bonds and differences of ground state energies of tert-butyl 4-phenyltetrahydroisoquinoline-2-carboxylate derivatives were determined by NMR spectroscopy. The results are discussed assuming characteristic intramolecular CH/pi interactions accompanied by results of X-ray structure analysis, ab initio MO, and DFT calculations. The calculated values with MP2/6-31G(d,p) level are in good agreement with the experimental results of X-ray structure analysis and NMR measurements.