Synthesis of trifluormethyl substituted oxetenes by the reaction of acetylenedicarboxylate with trifluoromethyl ketone in the presence of triphenylphosphine

In the presence of triphenylphosphine, dialkyl acetylenedicarboxylate 2 reacted smoothly with trifluoromethyl ketone 1 in toluene at room temperature affording the 2-trifluormethyl oxetenes 3 in good yields. These products are stable on heating or in the presence of some Lewis acids, such as ZnBr2, InCl3, and Cu(OTf)2.