HFIP-mediated cascade aminomethylation and intramolecular cyclization of allenamides with ,-acetals to access tetrahydro-β-carboline derivatives.

The construction of complex molecules under metal-free conditions multiple bond-forming steps in a cascade manner is highly desirable. Herein, we have developed an HFIP-alone promoted aminomethylation and intramolecular cyclization of allenamides, providing biologically relevant tetrahydro-β-carboline derivatives embedded with an allylic amine functionality. The metal-free protocol provided the desired tetrahydro-β-carboline derivatives under mild conditions. The potential of the protocol is further highlighted by the gram-scale reaction and synthesizing derivatives of biologically important molecules.