The design and development of an Ag(I)-promoted, highly diastereoselective cycloisomerization strategy for theO control experiment and identification of 18 O-labeled product suggested the involvement of an external water. The 7-azaindole substrates showned a distinct reactivity to give the (Z)-8-benzylideneoxazolo[3′,4′:1,5]pyrrolo [2,3-b]pyridines. Key features of this strategy are its 100% atom economy, access to important heterocycles, diverse substrate scope, yields up to 95%, operationally simple procedure, and distinct reactivity of indole vs 7-azaindoles.