Esters of trifluoromethane sulfonic acid have been synthesized by reaction of different alcohols with triflic anhydride and used in situ as initiators for the polymerization of tetrahydrofuran. Kinetic studies of the polymerization showed that allyl triflate has the highest reactivity and that an increase of the alkyl chain length of the initiator leads to a significant decrease of the initiation rate. "Non-linear" triflate ester such as isobutyl triflate leads to incomplete initiation. It was impossible to synthesize quantitatively the triflate from tert-butyl alcohol due to spontaneous elimination leading to isobutylene.