Recyclable gold(i)-catalyzed heterocyclization of ynamides with benzyl or indolyl azides towards 2-aminoindoles or 3-amino-β-carbolines

Abstract

A highly efficient heterogeneous gold(I)-catalyzed heterocyclization of ynamides with benzyl or indolyl azides has been achieved in 1,2-dichloroethane under mild conditions via a heterogenized α-imino gold carbene intermediate using 5 mol% of SBA-15-anchored strongly hindered NHC–gold(I) complex [IPr-SBA-15-AuNTf₂] as the catalyst, delivering a wide range of valuable 2-aminoindoles or 3-amino-β-carbolines in mostly good to excellent yields with high regioselectivity. Furthermore, the new heterogenized NHC–gold(I) complex displays the same catalytic activity as IPrAuNTf₂ and is facile to recover by centrifugation of the reaction mixture and can be reused at least seven times without any appreciable drop in its catalytic activity.