Preparation of cyclopropanone 2,2,2-trifluoroethoxy hemiacetals via oxyallyl cation

Abstract

Hemiacetals of cyclopropanone can be isolated and stocked, contrary to their highly reactive parent ketone. However, they are not readily converted to cyclopropanone, which limits their use as its synthetic equivalents. 2,2,2-trifluoroethoxy hemiacetals are expected to be better cyclopropanone surrogates, however, they have never been prepared, so far. We show that oxyallyl cations with a heteroatom in the -position can be intercepted with 2,2,2-trifluoroethanol, with formation of cyclopropanone trifluoroethoxy hemiacetals stable enough to be isolated, purified and characterized. These species can serve as synthetic equivalents of cyclopropanone under mild conditions.