Synthesis of Tryptamines from Radical Cyclization of 2‑Iodoaryl Allenyl Amines and Coupling with 2‑Azallyls

An efficient synthesis of tryptamines
is developed. Indole structures
were constructed using 2-iodoaryl allenyl amines as electron acceptors
and radical cyclization precursors. Radical–radical coupling
of indolyl methyl radicals and azaallyl radicals led to the tryptamine
derivatives. The utility and versatility of this method are showcased
by the synthesis of 22 examples of tryptamines in ≤88% yield.
In each case, indole formation is accompanied by in situ removal of
the Boc protecting group.