The Baeyer–Drewson indigo synthesis (1882) is an organic reaction in which indigo is prepared from 2-nitrobenzaldehyde and acetone The reaction was developed by von Baeyer in 1880 to produce the first synthetic indigo at laboratory scale. This procedure is not used at industrial scale. The reaction is classified as an aldol condensation. As a practical route to indigo, this method was displaced by routes from aniline. Mechanism Note In the English literature this reaction is usually called Baeyer–Drewson reaction, although the author of the original paper was called Drewsen. References External links Lab Manual Lab-synthesis of indigo Nitrogen heterocycle forming reactions Organic reactions Name reactions