Pictet-Spengler
Potentially produces regioisomers because of symmetric substructure definition.
SMARTS: [cH1:1]1:[c:2](-[CH2:7]-[CH2:8]-[NH2:9]):[c:3]:[c:4]:[c:5]:[c:6]:1.[#6:11]-[CH1;R0:10]=[OD1]>>[c:1]12:[c:2](-[CH2:7]-[CH2:8]-[NH1:9]-[C:10]-2(-[#6:11])):[c:3]:[c:4]:[c:5]:[c:6]:1
Conditions
Reactant 1: β-arylenylamine.
Reactant 2: aldehyde or ketone.
R1: H, alkyl. R2: alkyl.
References
Pictet, A.; Spengler, T. Ber. Dtsch. Chem. Ges. 1911, 44, 2030–2036
Other sources
Organic chemistry
Wikipedia