Heck反应那些事儿

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   经过三十多年的发展,Heck 反应的应用也越来越广泛。每一类反应根据其特点的不同由可以分成几类。

(一)分子内的 Heck 反应

  1. 生成烯基取代的反应

该类反应主要用于生成环外双键。环外双键是合成上一大难题,该反应成功的应用具有重大意义。目前已有合成的报道。

该反应还被 Danishefsky 应用到全合成 Taxol 上

示例:

分子内 Heck 反应化生成环外双键示例分子内 Heck 反应化生成环外双键示例

A stirred solution of 1 (98 mg, 0.19 mmol), triethylmine (0.32 mL, 2.3 mmol) and catalytic tetrakis(triphenylphosphine)palladium(0) (ca. 5 mg, 4 μmol) in 2.4 mL of acetonitrile was heated at 80 ℃ in a sealed tube under an argon atmosphere for 10 h. The reaction mixture turned dark orange after ca. 10 min, and the catalyst plated out on the walls of the tube as a shiny layer of palladium metal upon completion of the reaction. The reaction mixture was cooled to room temperature; the reaction was quenched with aqueous NaHCO 3 (15 mL), and the mixture was extracted with EtOAc (4×10 mL). The organic extracts were washed with aqueous NaHSO 3 (1×15 mL), water (1×15 mL), and brine (1× 15 mL) and dried over MgSO 4 . Filtration, concentration, and purification of the orange residue by flash column chromatography (45:55 Et 2 O/hexanes) gave 66 mg (90%) of 19 as a colorless solid: mp 193-194 ℃; Rf = 0.29 (8:2 Et 2 O/hexanes).

2.形成季碳中心的反应

      从 20 世纪 80 年代早期研究以来得到了广泛的应用。1989 年,Shibasaki 和 Overman首先报道不对称 Heck 反应.

实例

A mixture of Pd 2 (dba) 3 ·CHCl 3 (360 mg, 0.347 mol), (s)-BINAP (504 mg, 0.809 mol),and N,N-dimethylacetamide (DMA, 21 mL) was stirred at room temperature for 65 min. To the resulting orange solution was added a solution of compound 1 (1.82 g, 3.51 mol),1,2,2,6,6-pentamethylpiperidine (3.2 mL, 18 mmol), and DMA (18 mL), and the reaction was heated at 100 ℃ for 90 min. The result dark solution was poured into half-saturated aqueous NaHCO 3 (100 mL) and extracted with ether (3 × 150 mL). The combined organic extracts were washed with brine (100 mL), dried (MgSO 4 ), and concentrated, and the residue was  purified by sgc (9:1 → 1:1 hexane-EtOAc) to give oxindole enoxysilane compound 2 (1.29 g,94%) as a 98:2 mixture of geometric isomers: [α] 25 D –81 o (c 0.61 C 6 H 6 ).


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