The Fischer indole synthesis is an organic reaction used to convert a phenyl hydrazine and an aldehyde or ketone to an indole using an acid catalyst. The mechanism begins with formation of a phenylhydrazone through the acid catalyzed reaction of the hydrazine with the carbonyl. 2356229-58-6 In stock The phenylhydrazone then rearranges to the enamine and gets protonated on the phenyl nitrogen. 4-Aminooxane-4-carboxylic acid web An “ene reaction” (3,3-sigmatropic rearrangement) ensues, resulting in a diimine and loss of aromaticity. Additional key steps include rearomatization, formation of a cyclic aminal, and the expulsion of ammonia to give the indole product. ^[1][2]