1.1: TMSOTf; collidine / CH2Cl2 / 1 h / 0 °C 1.2: 85 percent / nBu4NF / tetrahydrofuran 2.1: 2,4,6-trichlorobenzoyl chloride; Et3N / tetrahydrofuran / 1 h / 20 °C 2.2: 60 percent / DMAP / toluene / 80 °C 3.1: 86 percent / TFA / CH2Cl2 / 0 °C 4.1: 71 percent / 2,4,6-triisopropylbenzenesulfonyl hydrazide; Et3N / diethyl ether / 39 °C 5.1: dimethyldioxirane / CH2Cl2 / -50 °C View Scheme

1.1: TMSOTf; collidine / CH2Cl2 / 1 h / 0 °C 1.2: 85 percent / nBu4NF / tetrahydrofuran 2.1: 2,4,6-trichlorobenzoyl chloride; Et3N / tetrahydrofuran / 1 h / 20 °C 2.2: 60 percent / DMAP / toluene / 80 °C 3.1: 86 percent / TFA / CH2Cl2 / 0 °C 4.1: 71 percent / 2,4,6-triisopropylbenzenesulfonyl hydrazide; Et3N / diethyl ether / 39 °C View Scheme