Asymmetric Dearomative Cyclization of Tryptamines with Allenamides

Abstract

Allenamides represent a versatile building block but has not been widely explored in asymmetric organocatalysis compared to the more traditional carbonyl and imine functionalities. An efficient enantio-discrimination of the chiral ion-pair between the protonated allenamide moiety and the chiral anion is crucial for the high enantiomeric excess. We envisioned this mode of catalysis may be applied to the dearomatizing tryptamine cyclization. Testing an array of chiral acid catalysts led us up to 96 %ee in the formation of hydropyrrolo[2,3,-b]indoles.Maste