1: 76 percent / DEAD, Ph3P / tetrahydrofuran 2: 78 percent / aq. AcOH / tetrahydrofuran / Ambient temperature 3: 80 percent / CrO3, H2SO4 / acetone / 0.5 h / Ambient temperature 4: 90 percent / aq. MeNH2 / ethanol / 1.5 h / Ambient temperature View Scheme