Abstract The reactions between aryl (trifluoromethyl)-substituted alkynes and arenes in triflic and fluorosulfonic acids were investigated. These reactions proceeded 100% regioselectively to give 1, 1-diaryl-2-trifluoromethylethenes in high yields. Depending on the workup conditions, 3, 3, 3-trifluoro-1, 1-diarylpropan-1-ol was also detected in the product mixture. The reaction mechanism was studied by both spectroscopic and theoretical ...