Gold Catalysis:Mild Conditions for the Synthesis of Oxazoles from N-Propargylcarboxamides and Mechanistic Aspects

摘要

2,5-Disubstituted oxazoles are synthesized from the corresponding propargylcarboxamides under mild reaction conditions via homogeneous catalysis by AuCI_3.While monitoring the conversion via 1H NMR spectroscopy,an intermediate 5-methylene-4,5-dihydrooxazole can be observed and accumulated up to 95%,being the first direct and catalytic preparative access to such alkylidene oxazolines.The intermediate was fully characterized and can be trapped at -25 C for several weeks.Deuteration experiments show a stereospecific mode of the two first steps of the reaction.