Copper (I)-mediated tandem A3 coupling/[3Â +Â 2] cycloaddition chemoselective synthesis of 4H-[1,2,3]triazolo[1,5-a]indoles

The copper (I) mediated tandem reaction of A3 coupling followed by a [3 + 2] cycloaddition methodology is developed for the first synthesis of structurally interesting 3-aryl/alkyl/silyl-4-amino-4H-[1,2,3]triazolo[1,5-a]indoles from various 2-azidobenzaldehydes, secondary amines, and terminal alkynes. The optimal reaction conditions of this one-pot tandem reaction are simple, performed at room temperature, and produce the corresponding products with high yields (up to 84%). The intermolecular [3 + 2] cycloaddition of 2-azidobenzaldehydes and terminal alkynes is found to be the competitive reaction for the presently developed tandem reaction with 2-triazole benzaldehydes as the minor products. The latter were also isolated and characterized.