Selectivity switch in the synthesis of vinylgold(I) intermediates
AuthorsHashmi, A. Stephen K
Schuster, Andreas M.
Nolan, Steven P.
KAUST DepartmentBiological and Environmental Sciences and Engineering (BESE) Division
KAUST Catalysis Center (KCC)
Physical Sciences and Engineering (PSE) Division
Chemical Science Program
Permanent link to this recordhttp://hdl.handle.net/10754/561930
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AbstractAn 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.
SponsorsThe 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.
PublisherAmerican Chemical Society (ACS)