1: 1) Et3N, n-Bu2BOTf 2) 30percent aq. H2O2 / 1) CH2Cl2, -78 deg C, 1 h, 0 deg C, 45 min; 2) MeOH, -78 deg C, 1 h, -78 - -45 deg C, 1 h 2: 89 percent / VO(acac)2, TBHP / CH2Cl2; benzene / 0 deg C, 3 h; RT, 1 h 3: 1) AlMe3 / 1) CH2Cl2, toluene, RT, 15 min; 2) CH2Cl2, -10 - 0 deg C, 1 h, 0 deg C, 2 h, RT, 0.5 h View Scheme

Multi-step reaction with 2 steps 1: 1) Et3N, n-Bu2BOTf 2) 30percent aq. H2O2 / 1) CH2Cl2, -78 deg C, 1 h, 0 deg C, 45 min; 2) MeOH, -78 deg C, 1 h, -78 - -45 deg C, 1 h2: 89 percent / VO(acac)2, TBHP / CH2Cl2; benzene / 0 deg C, 3 h; RT, 1 h