Coinage Metals-Catalyzed Cascade Reactions of Aryl Alkynylaziridines: Silver(I)-Single vs Gold(I)-Double Cyclizations

Alkynylaziridines carrying an aryl group could be efficiently converted into aminoallenylidene isochromans, isoquinolines, or tetrahydronaphtalenes with silver­(I) salts and into 1-azaspiro[4.5]­decane derivatives with gold­(I) complexes. Mechanistic investigations revealed that both Ag- and Au-catalyzed reactions involved a Friedel–Crafts type intramolecular reaction leading to an allene and that Au also rapidly promoted a second intramolecular cyclization of the aminoallene intermediate to the corresponding spiro derivative. Stereochemical investigations suggested an anti-SN2′-type pathway for the first cyclization leading to a stereodefined allene, which could then be cyclized to the corresponding stereodefined spiro product. These results highlight the duality between oxo- or azaphilicity and alkynophilicity of Ag and Au as well as their complementarity in terms of reactivity.