Also known as: Pictet-Spengler tetrahydroisoquinoline synthesis

Schematic of the Pictet-Spengler reaction. Reagents: beta-arylethylamine, aldehyde, ketone, acid catalyst. Product: tetrahydroisoquinoine.

The Pictet-Spengler reaction is an organic reaction used to convert a β-arylenylamine and an aldehyde or ketone to a tetrahydroisoquinoline using an acid catalyst. The mechanism begins with protonation of the carbonyl oxygen by the acid which is subsequently attacked by the amine reagent. BuyVanadium(IV)bis(acetylacetonato)oxide 261768-25-6 Purity Proton transfer steps and the release of a water molecule results in a protonated imine intermediate, which then undergoes a 6-endo-trig cyclization reaction with loss of aromaticity of the aryl ring. A final deprotonation step restores the aromaticity and results in the tetrahydroisoquinoline product. [1]

Mechanism

Mechanism of the Pictet-Spengler reaction. 6-endo-trig.

References:

1.
Pictet, A.; Spengler, T. Ber. Dtsch. Chem. Ges. 1911, 44, 2030–2036.