The Friedländer synthesis prepares quinolines from an ortho-acetylated nitrobenzene and a ketone. The synthesis begins with an aldol condensation in a basic medium. Reduction of the nitro group to amino allows cyclization by imine formation.

friedlander synthesis 01


friedlander synthesis 02

This synthesis can also be carried out by direct reaction of o-aminoacetophenone and an enolizable carbonyl in a basic medium.

friedlander synthesis 03

The mechanism can occur in two ways:

1. Formation of the imine, tautomerism to enamine and attack on the carbonyl
2. Aldol condensation and subsequent formation of the imine.