1: 61 percent / CrO3, H2SO4 / acetone / 1 h / -10 °C 2: 73.8 percent / acetic acid (glacial) / tetrahydrofuran; H2O / 168 h / Ambient temperature View Scheme

acetic acid in tetrahydrofuran; water 80 h; Ambient temperature;

1: 96 percent / pyridyne / 24 h / 4 °C 2: 88 percent / acetic acid (glacial) / tetrahydrofuran; H2O / 162 h / Ambient temperature View Scheme