One-Pot Aminoethylation of Indoles/Pyrroles with Alkynes and Sulfonyl Azides

A general and efficient one-pot aminoethylation of substituted indoles/pyrroles was accomplished for the synthesis of various tryptamine derivatives employing a combination of alkynes and sulfonyl azides as readily accessible aminoethylating agents. The reaction features a successful integration of copper-catalyzed alkyne and azide cycloaddition to N-sulfonyl-1,2,3-triazole, rhodium-catalyzed selective insertion of α-iminocarbenes onto the C3-H bond of indoles, and reduction of the resultant enamides to tryptamine derivatives employing either NaCNBH3 or palladium catalyst, in one-pot. The reaction also showed excellent functional-group tolerance and allowed the synthesis of various substituted tryptamines in good to excellent yield. This transformation constitutes a one-pot formal regioselective functionalization of terminal alkynes. Utility of the synthesized tryptamine was further demonstrated in the synthesis of dihydro-β-carboline and tryptoline.