烯烃化合物是含碳碳双键的一类化合物，因其双键的不饱和性，可以发生多种类型的氧化或者还原反应，构建出各种其他官能团，因而在有机化学中占有非常重要的地位，是合成各种化合物的重要中间体。

羟基消除制备烯烃是醇在酸性条件下经过E1机理生成烯烃的消除。酸的作用是对羟基进行质子化生成好的离去基团。

实例一

A solution of cyclohexanone (0.491 g,5 mmol) in 15 mL anhydrous THF was cooled to 0 ℃. Vinylmagnesium bromide (1.0 M in THF, 25 mL, 25 mmol) was then dropwise added, and the mixture was kept stirring for 2 h at 0 ℃.The reaction was quenched with saturated NH₄Cl (30 mL), and the aqueous layer was extracted by ether (20 ml × 3). The combined organic layer was dried over anhydrous Na₂SO₄. The solvent was distilled under low pressure. The residue was purified by silica gel column chromatography (eluent: EtOAc/hexane = 1/40) to give colorless oil I (0.35g, 56% in yield). I dissolved in 10 mL dry benzene was refluxed for 2h in a Dean-Stark apparatus. In the presence of p-toluene sulfuric acid (30 mg, 0.174mmol). The residue was purified by silica gel column chromatography (eluent:hexane) to give P (colorlessliquid, 0.15 g, 50%in yield).

Reference: Journal of Medicinal Chemistry, 2012.55(2), 971-975.

实例二

A 250 mL round-bottom flask equipped with a magnetic stir bar was charged with ketone A (0.32 g, 1.0mmol) and 1 M anhydrous HCl in methanol (100 mL). The reaction progress was monitored by TLC. After 2h, the starting material had been consumed. The solution was neutralized with 1 M NaOH, diluted with ethyl acetate (100mL), and washed with water (3 x 50 mL). The combined organic layer was dried over MgSO₄, filtered, and concentrated, furnishing 0.29 g (83%). Rf = 0.46 (50% ethyl acetate inhexane).

Reference: Organic Letters, 2012.14(2), 632-635.

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