Skraup Synthesis

the synthesis of quinoline and quinoline analogues and derivatives by the reaction of aniline (I) (or aniline’s corresponding analogues and derivatives) with glycerine in the presence of a dehydrating agent (usually sulfuric or phosphoric acid) and an oxidizing agent (usually nitrobenzene or a derivative of nitrobenzene corresponding to a particular aniline derivative). Under the action of the dehydrating agent, glycerine is converted to acrolein (II), which then participates in the main reaction:

where X designates an organic radical, a halogen, or a group such as—NO₂.

The reaction was discovered in 1880 by Z. H. Skraup. It is used in the laboratory and in industry for the synthesis of pharmaceutical preparations and photosensitizers.