The Wolff–Kishner reduction is a reaction used in organic chemistry to convert carbonyl functionalities into methylene groups. In the context of complex molecule synthesis, it is most frequently employed to remove a carbonyl group after it has served its synthetic purpose of activating an intermediate in a preceding step. As such, there is no obvious retron for this reaction. Originally reported by Nikolai Kischner in 1911 and Ludwig Wolff in 1912, it has been applied to the total synthesis of scopadulcic acid B, aspidospermidine and dysidiolide.