Synthesis of Substituted Quinolines via a Heteroannulation Process

Significance

Reported is the synthesis of substituted quinolines by a two-step, one-pot method. This proceeds through conjugate addition of an aniline to a propynone to form enaminone A which, when subjected to basic conditions, undergoes cyclization to form the quinoline derivative. Initially, this reaction was performed in two discrete steps. However, a more convenient process was developed, whereby the volatile material is removed under reduced pressure between the steps with no purification of the enaminone. Unfortunately, a common solvent for both steps was not found. Metal catalysis (Cu, Pd, Au) was shown to lead to N-vinylic indoles, but this reaction was not elaborated upon.