“…PTSA (380 mg, 2 mmol) was added to the solution of crude 3c in MeOH (25 mL) and the mixture was heated under reflux for 15 h with stirring. The crude product 1c was purified by TLC (Merck precoated plates, R f 0.65 hexane/ethyl acetate, 10:1, twice) to afford the title compound (80 mg, 38%) as a C 5 ), 53.9 (s, C(CH 3 ) 2 ), 50.5 (s, CH 2 ), 27.5 (s, CH 3 ); 19 The reaction of 2d (273 mg, 1 mmol) and 2-methylbut-3-yn-2-ol (126 mg, 1.5 mmol) gave the crude compound 3d (the 1 H and 19 F NMR spectra agreed with the data reported [12] The reaction of 2e (291 mg, 1 mmol) and 2-methylbut-3-yn-2-ol (126 mg, 1.5 mmol) gave the crude compound 3e [12]. Then PTSA (190 mg, 1 mmol) was added to the solution of crude 3e in MeOH (25 mL) and the mixture was heated under reflux for 40 h with stirring.…”