Conformation of the methyl group and tetrahydropyridine ring in N-acyltetrahydroquinaldine derivatives

NMR spectra of N-acyletrahydro quinaldines 12–19 and of pyridodibenzoxazepines 21–24 show the Me group to be axially oriented with the tetrahydropyridine ring in a half-boat conformation. The aroyl phenyl in both is twisted out of the CO plane. While the Me group again occupies the axial position in pyridophenanthridones 5 and 7 and pyridooxazinones 8 and 9, the tetrahydropyridine ring exists as a half-chair.