The Baeyer-Drewson indigo synthesis (1882) is an organic reaction in which indigo is prepared from o-nitrobenzaldehyde and acetone
The reaction is classified as a Aldol condensation. As a practical route to indigo, this method was displaced by routes from aniline.
In the English literature this reaction is usually called Baeyer-Drewson reaction, although the author of the original paper was called Drewsen.
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