tetrabutyl ammonium fluoride in tetrahydrofuran 0.25 h;

Multi-step reaction with 2 steps 1: 60 percent / CrO3, pyridine, Ac2O / CH2Cl2 2: 1) sodium 2-methyl-2-butoxide / 1) Et2O, benzene, 2h, 2a) -70 to -10 deg C, 1h, 2b) 4 deg C, 48h