Gold(I)-NHC-catalysed synthesis of benzofurans via migratory cyclization of 2-alkynylaryl ethers
Quang Le1, Christopher C Dillon1, Dana A Lichtenstein1
1California State University Fresno, 2555 E San Ramon Ave M/S SB70, Fresno, CA 93740, USA. hmuchalski@csufresno.edu.
Abstract:
Homogeneous cationic gold(i) catalysis emerged as a preferred avenue for the activation of alkenes and alkynes towards reactions with weak nucleophiles, especially in cyclization reactions. Here we report an intramolecular carboalkoxylation reaction of electron-rich benzyl ethers of 2-ethynylaryl phenols catalysed by a digold(i)-NHC complex. The reaction proceeds efficiently with low catalyst loading and the resulting 2,3-disubstituted benzofurans form in moderate to good yields. Based on the results of a cross-over experiment, spectroscopic data, and DFT calculations, we propose a mechanism that accounts for the observed chemo- and regioselectivity.
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