1: 1. boron trifluoride etherate 2. m-chloroperoxybenzoic acid / 1. CH2Cl2, r.t., 20 h 2. CH2Cl2, 30 min 2: acetic acid, 15-crown-5 / CH2Cl2; H2O / 10 h / Ambient temperature 3: HOAc, H2SO4, H2O / 10 h / 100 °C 4: 1. SOCl2 / 1. reflux, 30 min 2. toluene, r.t., 30 min 5: potassium tert-butoxide / tetrahydrofuran / 0.5 h / 25 °C View Scheme

1: 1. boron trifluoride etherate 2. m-chloroperoxybenzoic acid / 1. CH2Cl2, r.t., 20 h 2. CH2Cl2, 30 min 2: acetic acid, 15-crown-5 / CH2Cl2; H2O / 10 h / Ambient temperature 3: 80 percent / H2SO4 / 12 h / 80 °C 4: 68 percent / MeONa / tetrahydrofuran / 0.5 h / 15 °C View Scheme