From Propargylic Amides to Functionalized Oxazoles: Domino Gold Catalysis/Oxidation by Dioxygen

A new, highly efficient, and atom-economic access to
a series of functionalized 2,5-disubstituted oxazoles from propargylic
amides is reported. A series of propargylic amides were transformed
to the corresponding alkylideneoxazolines by a gold­(I) catalyst. The
next step was an autoxidation to hydroperoxides bearing the heteroaromatic
oxazoles. Experiments addressing the reaction mechanism reveal a radical
pathway for this autoxidation process. The hydroperoxides could conveniently
be converted to the corresponding alcohols by reduction with sodium
borohydride.