HUSY zeolite-promoted reactions of trifluoromethylated propargyl alcohols with arenes: synthesis of CF3-indenes and DFT study of intermediate carbocations.

The reaction of CF3-propargyl alcohols [ArC[triple bond, length as m-dash]CCH(OH)CF3] with arenes under the action of acidic HUSY zeolite CBV-720 was investigated. It was found that the reaction at 100 °C for 1 h gave rise to 3-aryl-1-CF3-indenes in up to 83% yield. Electronic characteristics of the reaction key intermediates, mesomeric CF3-propargyl-allenyl cations [ArC[triple bond, length as m-dash]C-HC+(CF3) ↔ ArC+[double bond, length as m-dash]C[double bond, length as m-dash]CH(CF3)], were studied by DFT calculations. A plausible cationic reaction mechanism is discussed.