Novel synthesis of 3-alkyl-2,5-diaryl-1,4-oxathiepin-7-ones

N-Acetyl-N-methyl-3-aryl-3-[1-(aroyl)ethylthio]-2-propaneamides, prepared from thioaroylketene S,N-acetals, Hg(OAc)2 and silyl enol ethers of aryl-1-propanones in CH2Cl2 at rt, reacted with NaH in THF to give the title compounds in excellent yields.