Carbon-13 magnetic resonance studies of cyclic compounds. Part I. Piperidines and decahydroquinolines

Abstract

Details are reported for proton decoupled 13C spectra of N-methyl- and C-methyl-piperidines, measured by the pulsed Fourier transform technique. The results yield chemical shift parameters, for ring carbons in six-membered rings, corresponding to the replacement of CH2 by NH, of CH2 by CHMe, and of NH by NMe. The predicted 13C shifts of trans-decahydroquinoline, and of both major and minor conformations of cis-decahydroquinoline, agreed well with the experimental data obtained at room temperature (trans) and at –74°(cis), where signals for both major (93·5%) and minor (6·5%) conformations of the cis-molecule were observed.