Synthesis of 5-Amino-3(2)-furanones via -Methylation/Intramolecular Cyclization of γ-Sulfanylamides.

The -methylation/intramolecular cyclization of γ-sulfanylamide is depicted. Different methylating reagents were successfully employed for -methylation, depending on the substituent pattern of the amide in the starting γ-sulfanylamides; trimethyloxonium tetrafluoroborate was used for -aryl substituted γ-sulfanylamides, and the combination of methyl iodide and silver(I) tetrafluoroborate was used for -alkyl substituted γ-sulfanylamides. When the resulting sulfonium salt was treated with DBU, it smoothly underwent intramolecular cyclization to produce a series of -aryl, -alkyl, -dialkyl or -alkyl--aryl substituted 5-amino-3(2)-furanones in 55%-quantitative yields.