Ag(I)-Promoted, Diastereoselective Cyclo-isomerization of N‑Alkynyl-7-azaindole-2-carbinols. Selective Synthesis of syn-1,2-Diarylpyrrolo[1,2‑a]indol-3-ones and (Z)‑8-Benzylideneoxazolo[3′,4′’:1,5]pyrrolo[2,3‑b]pyridines

The design and development of an Ag­(I)-promoted, highly diastereoselective cycloisomerization strategy for the synthesis of syn-1,2-diarylpyrrolo­[1,2-a]­indol-3-ones from N-alkynyl-indole-2-carbinols is reported. The H2 18O control experiment and identification of 18O-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.