烯烃用 OsO4/NaIO4 合成醛氧化
与臭氧化法相比，OsO 4 /NaIO 4 是一种温和的烯烃氧化开裂法，在天然产物合成中很有用。烯烃先与 OsO 4 反应生成锇酸酯，再用过碘酸钠氧化，发生开裂，在生成羰基化合物的同时，OsO 4 再生，所以 OsO 4 用催化量即可。当生成的醛易于分子内缩合时，反应最好在两相系统中进行。 烯烃用 OsO 4 /NaIO 4 氧化合成醛反应示例：
N-Benzyl-3-(Z/E)-ethylideneazetidin-2-one (5.0 g, 26.7 mmol) is dissolved in 150 mL of methanol and 100 mL of water contained in a 500-mL, one-necked, round-bottomed flask. Sodium metaperiodate (14.3 g, 67.0 mmol) is introduced, followed by approximately 40 mg of osmium tetraoxide. The reaction mixture is stirred vigorously for 12 hr under nitrogen, treated with Celite (6 g), and agitated for an additional hour prior to filtration. The filtrate is concentrated to 1/3 of its volume under reduced pressure, then extracted with ethyl acetate (2× 200 mL). The combined organic phases are washed once with brine, dried, and concentrated to leave a dark brown oil. This oil is flushed through a short pad of silica gel (8 cm × 8 cm) using dichloromethane as eluant (900 mL). The pure fractions are pooled and evaporated to give a clear pale yellow oil, which crystallizes on prolonged standing at 5°C. The yield of N-benzylazetidine-2,3-dione is 3.12-3.64 g (66.7-77.9%).
烯烃经由有机硼化合物中间体的烯烃甲酰化合成醛 烯烃与甲硼烷反应所得的有机硼化合物能用各种方法转变为醛。用铬酸氧化时，所得醛的碳原子数不变。如与一氧化碳反应再进行氧化便得多一个碳原子的醛。要是与重氮乙醛反应，即可得增长二个碳原子的醛。通过与丙烯醛的加成，碳原子数可增加三个。 由烯烃的加氢甲酰化合成醛（羰基合成法） 将烯烃与水煤气（CO 和水的混合物）在钴、铑等催化剂存在下进行反应反应可得延长一个碳的醛。工业上需要高温高压下进行。将催化剂改良可使反应在常温常压下进行，已经有了实验室很有用的醛的合成法 由烯烃的加氢甲酰化合成醛（羰基合成法）反应示例：
To a stainless-steel, 0.5-l. pressure vessel equipped with a 450-atm. manometer and a temperature recorder is added 0.2 g. (0.8 mmole) of rhodium(III) oxide. The vessel is sealed and evacuated to 0.1 mm. pressure. A solution of 82 g. (1.0 mole) of cyclohexene in 140 ml. of anhydrous benzene is introduced by suction into the vessel. The vessel is placed in a heatable shaking device and pressured to 75 atm. with carbon monoxide; the total pressure is then increased to 150 atm. with hydrogen. Shaking is begun and the vessel is heated to an internal temperature of 100°. When the internal temperature reaches 100°, the pressure begins to fall. Whenever the pressure falls to 60 atm., rocking is stopped and the pressure is first increased to 105 atm. with carbon monoxide, then to 150 atm. with hydrogen. Rocking is started again, and the process is continued until no appreciable pressure decrease occurs. Approximately 2 hours is required, and the pressure decrease corresponds to the consumption of 2 moles of gas. The vessel is rapidly cooled to room temperature and the residual gas is carefully vented.
The vessel is opened, and the slightly yellow reaction mixture is transferred immediately to a 2-l., round-bottomed flask containing a freshly prepared solution of 200 g. of sodium hydrogen sulfite in 400 ml. of water. The flask is fitted with a stopper and is occasionally shaken at room temperature for a period of 3 hours. The resulting precipitate is collected by suction filtration on a sintered-glass funnel and washed with 500 ml. of diethyl ether. After drying in air, the bisulfite derivative is transferred to a 2-l. distillation flask containing 1 l. of 20% aqueous potassium carbonate. The resulting mixture is distilled, and the azeotropic mixture of water and aldehyde (b.p. 94–95°) is collected under nitrogen.
The aldehyde is separated from the lower aqueous layer as a colorless liquid, dried over 10 g. of anhydrous sodium sulfate, filtered, and distilled under reduced pressure using a Claisen distillation apparatus, yielding 92–94 g. (82–84%) of cyclohexanecarboxaldehyde, b.p. 52–53° (18 mm.), n D 25 1.4484. A purity of about 98% was established by GC analysis; the product is suitable for synthetic use without further purification.
