Heterogeneous Catalysts in Pictet‐Spengler‐Type Reactions

Abstract

Several solid catalysts were evaluated as an alternative for 1,2,3,4-tetrahydroisoquinoline synthesis by means of the Pictet-Spengler reaction. The reaction catalysed by a mixed oxide (Mg and Al) led to the best yield and good regioselectivity; using an Al-pillared bentonite led to good yields and total regioselectivity. The results revealed no direct relationship between catalyst acidity and yield.

Porous Catalytic Systems in the Synthesis of Bioactive Heterocycles and Related Compounds

“…Recently, Quevedo et al evaluated different solids as catalysts-a natural bentonite from Colombia, homogenized calcium bentonite, Al-pillared bentonite, a mixed oxide (Al 2 O 3 -MgO, M 3+ /(M 2+ +M 3+ ) = 0.5), and an Al-Zr pillared vermiculite-in the Pictet-Spengler reaction between dopamine hydrobromide and aromatic aldehydes to synthetize the 1,2,3,4-tetrahydroisoquinoline [141]. The best yields, up to total conversion, were obtained when the mixed oxide was used as catalyst.…”

Role of hydroxyl groups on the aromatic ring in the reactivity and selectivity of the reaction of β-phenylethylamines with non-enolizable aldehydes

“…The Pictet-Spengler reaction involves the formation of an imine or iminium ion from an aldehyde and a b-arylethylamine followed by cyclization through an intramolecular aromatic electrophilic substitution in the presence of a catalyst [1][2][3]. Commonly, the amines used have benzene or indole rings as an aromatic nucleus, forming 1,2,3,4-tetrahydroisoquinolines (THIQ) and 1,2,3,4-tetrahydro-b-carbolines (THBC), respectively.…”