Fischer indole
Potentially produces regioisomers because of symmetric substructure definition.
SMARTS: [NH1;$(N-c1ccccc1):1](-[NH2])-[c:5]:[cH1:4].[C;$(C([#6])[#6]):2](=[OD1])-[CH2;$(C([#6])[#6]);!$(C(C=O)C=O):3]>>[C:5]1-[N:1]-[C:2]=[C:3]-[C:4]:1
Conditions
Reactant 1: phenylhydrazine.
Reactant 2: aldehyde or ketone.
References
Fischer, E.; Jourdan, F. Ber. Dtsch. Chem. Ges. 1883, 16, 2241–2245.
I.-K. Park, S.-E. Suh, B.-Y. Lim, C.-G. Cho, Org. Lett., 2009, 11, 5454-5456.
Other sources
Organic chemistry
Wikipedia