Formation of C-Amido-calix[3]indoles from 2′- and 7′-Indolylglyoxylamides

A range of 2′- and 7′-indolylglyoxylic amides 1 and 2, derived from 3-(4′-chlorophenyl)-4,6-dimethoxyindole, have been reduced to the corresponding alcohols 3 and 4 respectively. On treatment with acid, these alcohols underwent trimerisation to give the calix[3]indoles 8. The major conformer was generally the flattened partial cone, but in certain cases the cone conformers could be detected and even isolated. The related 2′-indolylglyoxylic amides 13, derived from 4,6-dimethoxy-3-methylindole, were also converted into calix[3]indoles 15.