活性二氧化锰氧化
反应实例
A 500-mL, round-bottomed flask, equipped with a Teflon-coated magnetic stirring bar, is charged with the 11.2 g of allylic alcohol and 300 mL of dichloromethane, and the resulting vigorously stirred solution is treated with 33 g of active manganese dioxide (380 mmol). Additional 2–5 g lots of the oxidant are added every 2–3 hr until the reaction is complete. The reaction mixture is vacuum-filtered through a pad of diatomaceous earth, and the pad is washed with 200 mL of dichloromethane. The resulting clear filtrate is concentrated carefully using a rotary evaporator, and the residual oil is purified by bulb-to-bulb distillation at 0.3 mm (pot temperature 100 °C) affording 8.43–8.71 g (87–90%) of enone as a pale yellow oil that solidifies when cooled below 15°C. Crystallization of the crude product from pentane at −70 °C gives (4S)-(−)-tert-butyldimethylsiloxy-2-cyclopenten-1-one as colorless needles having mp 32–33 °C, [α]D23 −65.1° (CH3OH, c 0.94).
【Organic Syntheses, Coll. Vol. 9, p.136; Vol. 73, p.44】
A 100-mL, one-necked, round-bottomed flask is fitted with an efficient reflux condenser and arranged for magnetic stirring and heating. The flask is charged with 50 mL of pentane and 2.0 g (13 mmol) of alcohol. To the rapidly stirred solution is added 16 g (180 mmol) of activated manganese (IV) oxide in small portions over 5 min. The solution is heated at reflux for 18 hr and then an additional 8 g (90 mmol) of activated manganese (IV) oxide is added in portions. After being heated at reflux for 24 hr, the reaction mixture is filtered through a 2-cm Celite filter pad. The filtered manganese oxides are thoroughly washed with about 200–300 mL of dichloromethane. Evaporation of solvent from the combined filtrates leaves 1.4–1.6 g of a light yellow oil. Bulb-to-bulb distillation at 100°C/0.1 mm gives 1.27–1.40 g (8.4–9.3 mmol, 64–71% yield) of an oil 3-Butyroyl-1-methylpyrrole.
【Organic Syntheses, Coll. Vol. 7, p.102; Vol. 62, p.111】
【Zh. Org. Khim., 1971, 7, 21210 (CA 1972, 76, 13712)】
【Chem. Ber., 1977, 110, 3664】
【J. Chem. Soc., 1963, 4983】
【Synthesis, 1988, 715】
活性二氧化锰的制备方法
【J. Chem. Soc. 1952, 1094】
实验技巧
※ 不同的公司的二氧化锰活性纯度不同。
※失活的主要原因是二氧化锰能结合一分子的结晶水,处理方法是碾碎后两百度以上高温长时间加热,能恢复活性。
参考文献
一、化学空间:http://www.chem-station.com/cn/reactions/2014/05/活性二氧化锰-activated-manganese-dioxide-mno2.html
二、药明标准操作
三、《现代有机合成试剂——性质、制备和反应》,胡跃飞等编著,151-152