The Doebner-Miller synthesis of quinolines under modified
biphasic conditions was investigated. Crotonaldehyde, reacted readily
with aniline to produce 2-methylquinoline. However, cinnamaldehyde
and other γ-substituted α,β-unsaturated
aldehydes yielded complex mixtures with substituted anilines to
provide only trace quantities of quinolines. The Doebner-Miller
reaction under these conditions is only suitable for sterically
accessible α,β-unsaturated aldehydes.
α,β-unsaturated aldehyde - aniline - quinoline - Doebner-Miller reaction - heterocycle