Synthesis of Substituted Furans via Silica-Supported Silver Catalysis
S. J. Hayes, M. D. Menzies, M. O’Halloran, W. Tan, D. W. Knight*
Cardiff University and GlaxoSmithKline, Irvine, UK
22. November 2007 (online)
A synthesis of substituted furans from 3-alkyne-1,2-diols using silver nitrate supported on silica gel under mild conditions is reported. The reaction has been explored for several substitution patterns (2,5; 2,4; 2,4,5) with a modest range of functional group variation. Limitations are outlined: R3 ∂ H, thiofuran (and, by inference, divalent sulfur) functionalities are not tolerated, and possible 5-exo-dig processes can compete with the desired 5-endo-dig transformation. An application to the synthesis of a sesquirosefuran isomer from a citronellol-derived diol in 97% overall yield is reported as a utilization of the method. Experimental detail on the formation of the diol was not given.