Stereoselective preparation of trifluoromethyl containing 1,4-oxathiolane derivatives through ring expansion reaction of 1,3-oxathiolanes

Trifluoromethyl containing 1,4-oxathiolanes are synthesized in excellent yields and high stereoselectivities from the expansion reactions of sulfur ylide intermediates, which were prepared from the reaction of 2-diazo-3,3,3-trifluoro-propionic acid methyl ester and 1,3-oxathiolanes in the presence of Rh2(OAc)4.