烯烴及芳環(huán)的 C=C 雙鍵經(jīng)臭氧、氧化鋨等作用而氧化斷裂生成醛，是醛的重要合成法之一。此外，將烯烴變?yōu)槿┑姆椒ㄉ杏杏迷?Rh 及 Co 催化下與氫及一氧化碳起反應(yīng)的加氫甲?；?，硼氫化反應(yīng)以及將芳環(huán)上的 C-H 直接轉(zhuǎn)化為 Li 而起甲?；磻?yīng)等。
烯烴經(jīng)加成-氧化、加成-還原、加成-水解、加成異構(gòu)化以及一氧化碳插入反應(yīng)等則能合成酮。
由烯烴臭氧氧化合成醛 烯烴及芳香環(huán)等與臭氧反應(yīng)，先生成過氧化物，由于有爆炸危險(xiǎn)不予分離，直接將其還原為醛。還原可用催化氫化、鋅、碘化鈉、磷化氫類化合物、亞磷酸、甲硫醚等方法。要是不予還原則經(jīng)氧化分解得酸。 有多個(gè)雙鍵共存時(shí)，臭氧化的選擇性一般在電子密度高而位阻小的雙鍵。芳香環(huán)的反應(yīng)較遲鈍，有不飽和側(cè)鏈存在時(shí)優(yōu)先選擇氧化側(cè)鏈雙鍵。含雜原子的芳環(huán)對(duì)臭氧的穩(wěn)定性大于苯環(huán)。 由烯烴臭氧氧化合成醛示例 1 ：
A dry, 100-mL, round-bottomed flask containing a magnetic stirring bar is fitted with an inlet adapter for ozonolysis and charged with 1-cyclopenteneacetonitrile (5.0 g, 46.7 mmol, and 60 mL of dry dichloromethane. A gentle stream of dry ozone is passed through the solution and the flask is immediately cooled to ?78°C. Ozonolysis is continued until the distinctive blue color of excess ozone is first observed, ozonolysis is then terminated, and the excess ozone is removed by purging with a stream of nitrogen for 5-10 min. The solution is allowed to warm to room temperature, the ozonolysis adapter is replaced with a rubber septum, and neat dimethyl sulfide (3.9 g, 62.1 mmol) is added via syringe. The solution is allowed to stir at room temperature for 36 hr during which time the solution changes in color from a pale yellow to dark red. The resulting solution is concentrated under reduced pressure using a rotary evaporator, and the resulting thick, red syrup is diluted with 40 mL of ethyl acetate and washed with water (3 × 25 mL. The aqueous phase is extracted with ethyl acetate (3 × 25 mL), the organic phases are combined, rinsed with brine in order to remove all DMSO, dried (MgSO 4 ), filtered, and concentrated. The residual red oil (5.55 g, 98%) contains only trace impurities and can be used without purification in most cases. If required, further purification is achieved by rapid radial chromatography on a 2-mm plate using the solvent delivery tip designed for a 4-mm plate and eluting with 50% ethyl acetate-hexane. The desired fractions are combined and concentrated to provide 1-oxo-2-cyclohexenyl-2-carbonitrile (4.8g, 85% yield) as a pink oil.
由烯烴臭氧氧化合成醛示例 2：
A 500 mL, three-necked, round-bottomed flask is fitted with a glass tube to admit ozone, a calcium chloride drying tube, a glass stopper, and a magnetic stirring bar and is charged with 6.161 g of cyclohexene (0.075 mol), 250 mL of dichloromethane, and 50 mL of methanol. The flask is cooled to ca. ?78°C (2-propanol–dry ice), and ozone is bubbled through the solution with stirring. When the solution turns blue, ozone addition is stopped. Nitrogen is passed through the solution until the blue color is discharged and then the cold bath is removed. The drying tube and ozone inlet are replaced with a stopper and rubber septum, and 1.215 g of p-toluenesulfonic acid (TsOH) (10% w/w) is added. The solution is allowed to warm to room temperature as it stirs under an atmosphere of nitrogen for 90 min. Anhydrous sodium bicarbonate (2.147 g, 4 mol-equiv) is added to the flask and the mixture is stirred for 15 min, and then 12 mL of dimethyl sulfide (0.150 mol) is added. After being stirred for 12 hr, the heterogeneous mixture is concentrated to approximately 50 mL by rotary evaporation. Dichloromethane (100 mL) is added and the mixture is washed with 75 mL of water. The aqueous layer is extracted with two more 100-mL portions of dichloromethane,and the combined organic layers are washed with 100 mL of water. After extracting the aqueous layer with 100 mL of dichloromethane, the organic layers are dried over anhydrous magnesium sulfate, filtered, and concentrated by rotary evaporation. Short-path distillation of the crude product gives 8.2–8.4 g of 6,6-dimethoxyhexanal, 68–70%, bp 80–82°C/1.75 mm.
