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Mitsunobu 硫代反应2020-05-09

活化的硫亲核试剂也能参与Mitsunobu反应,生成手性翻转的硫酯或硫醚。Merck的Volante第一次报导了这种方法。

芳香类硫醇化合物都有足够的活性参与这种反应。Knutsen等报导了这种类型的应用。

Mitsunobu 法合成硫醚方法示例

To a solution of 2-[(R)—N-(tert-butyloxycarbonyl)amino]-1-propanol (15 g, 85.6 mmol) in THF (200 mL) was added 2-mercaptobenzothiazole (14.3 g, 85.6 mmol) and PPh3 (24.7 g, 94.2 mmol). After stirring for 0.25 h a solution of DEAD (14.8 mL, 94.2 mmol) in dry THF (100 mL) was added dropwise over 0.5 h. The reaction mixture was stirred for 1 h at 20oC and filtered. The filtrate was evaporated and stirred with EA (100 mL), and the product was collected by filtration (20.66 g, 74%).

Mitsunobu 卤代反应

在Mitsunobu 反应中,用卤原子取代羟基生成卤代物也有报导,但其应用还不多见。Falck 等报导了通过Mitsunobu 过程合成一系列的卤代烃,除了氟代的产率不高以外,氯代,溴代和碘代的产率都不错。

Joulle 等报导脯胺酸衍生物在经过Mitsunobu 过程后得到手性翻转的碘代产物。反应首先是生成一个甲醚中间体,然后在三苯膦的作用下发生碘代,同时手性翻转。

Mitsunobu 法合成卤代物方法示例

To a flame-dried round-bottomed flask eguipped with a magnetic stir bar and an addition funnel under N2 was added N-Boc-trans-4-hydroxy-L-proline methyl ester (19.29 g, 0.079 mol), triphenylphosphine (24.78 g, 0.094 mol) and anhydrous THF (2755 mL). The solution was cooled to 0oC. Diethyl azodicarboxylate (DEAD, 14.9 mL, 0.094 mol) in anhydrous THF(15 mL) was added dropwise, followed by the addition of methyl iodide (5.88 mL, 0.094 mol).Upon addition of MeI, the solution turned from dark brown to bright yellow. The reaction mixture was allowed to warm to ambient temperature and stirred for 10 h. The solvent was removed under reduced pressure and the crude oil was purified by column chromatograghy。eluting with 5% EA/PE to afford the desired product as a white solid (26.22 g, 93.8%).

其他手性翻转试剂

(1) Vilsmeier 试剂:(cloromethylene)dimethylammonium chloride

由DMF和草酰氯制,和醇生成亚胺盐后再经过亲核取代得到胺。

(2) DPPA 和DBU

Merck 的Thompson 和Grabowski 用DPPA 和DBU 也实现了手性翻转,

得到叠氮化合物。

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