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

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posted on 2012-05-04, 00:00 authored by Nicolas Kern, Aurélien Blanc, Solène Miaskiewicz, Michelle Robinette, Jean-Marc Weibel, Patrick Pale
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.

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