1: N-bromosuccinimide, MgO, H2O / dimethylformamide / 2 h / Ambient temperature 2: 71 percent / NaOMe / methanol; tetrahydrofuran / 8 h / 4 °C 3: 71 percent / KHS, 18-crown-6 / ethane-1,2-diol / 2 h / 140 °C 4: 27 percent / p-TSA / acetone / Ambient temperature View Scheme

tribromo methane; potassium tert-butylate; toluene-4-sulfonic acid 1.) Et2O, -30 deg C, 24 h, 2.) acetone, TsOH, 2 h; Yield given. Multistep reaction. Yields of byproduct given;

potassium tert-butylate; toluene-4-sulfonic acid 1.) Et2O, -30 deg C, 24 h, 2.) acetone, TsOH, 2 h; Yield given. Multistep reaction. Yields of byproduct given;

1: N-bromosuccinimide, MgO, H2O / dimethylformamide / 2 h / Ambient temperature 2: 71 percent / NaOMe / methanol; tetrahydrofuran / 8 h / 4 °C 3: 1) N,N,N',N'-tetramethylethylenediamine, 2) n-BuLi, CuI / 1) a) ethyl ether, dry ice, acetone bath, b) -15 deg C, 45 min, 2) -15 deg C, 20 min, 3) -20 deg C, 24 h 4: 0.25 g / p-TSA / acetone / 18 h / Ambient temperature 5: 93 mg / 1.0 M NaOH / methanol / 2 h / Heating View Scheme