Chemistry of tropan-3-yl ethers. Part II. Configuration and conformation of phenyl tropan-3-yl ethers

Abstract

The configuration at C-3 of the epimeric phenyl tropan-3-yl ethers has been investigated by i.r. and n.m.r. spectroscopy. In the ether prepared from tropan-3α-yl methanesulphonate the C-3–O bond is in the β position, and in that obtained with 3α-chlorotropane it is in the α position. Dipole moment and Kerr constant data indicate that the piperidine ring of the tropane skeleton is in a chair conformation and show that the N-methyl group is equatorial. Comparison of the measured and calculated dipole moments of the epimeric p-chlorophenyl tropan-3-yl ethers shows that steric repulsion between the substituent in the 3α-position and the ethylene bridge distorts the tropane skeleton.