Pictet–Spengler reaction is a chemical reaction in which a β-arylethylamine undergoes condensation with an aldehyde or ketone followed by ring closure. This kind of reaction is a century old technique for the construction of aza-cycles. The Pictet-Spengler reaction is a straightforward approach toward the construction of nitrogen containing heterocycles through C-C bond formation. This Mannich-type cyclization involves an intramolecular aromatic electrophilic substitution mechanism of electron-rich aromatic or heteroaromatic rings to an imine or iminium ion. In order to obtain chiral aza-cycles Cinchona alkaloid catalysts can be used.