An unexpected regioselectivity reversal was observed in the synthesis of vinylgold(I) complexes from propargyl carboxamides. The use of [Au(IPr)(OH)] affords preferentially vinylgold(I) complexes resulting from a 5-exo-dig cyclization, whereas the use [Au(IPr)]+ species, generated in situ starting from [Au(IPr)(Cl)] and AgOTf, leads to vinylgold(I) complexes which form via a 6-endo-dig cyclization, This unexpected "selectivity switch" for this cyclization led us to propose two different reaction pathways enabling the formation of the two different products. One mechanism involves the [Au(IPr)]+ species with "classical" I activation of the alkyne framework of the carboxamides, and the second represents an "unusual" use of the basic Brønsted character of [Au(IPr)(OH)]. Mechanistic and DFT studies support the mechanistic hypotheses. © 2011 American Chemical Society.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The ERC (FUNCAT to SPN) and the EPSRC are gratefully acknowledged for support of this work. A.P. thanks the Spanish MICINN for a Ramon y Cajal contract (RYC-2009-04170). Umicore AG and Chemetall AG are thanked for their generous gifts of materials. S.P.N. is a Royal Society Wolfson Research Merit Award holder. We thank Dr. Pierrick Nun for valuable discussions.
ASJC Scopus subject areas
- Organic Chemistry
- Physical and Theoretical Chemistry
- Inorganic Chemistry