CONVENIENT TWO-STEP CONVERSION OF LACTONES INTO CYCLIC ETHERS
CONVENIENT TWO-STEP CONVERSION OF LACTONES INTO CYCLIC ETHERS
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内酯便捷地两步转化为环醚
DOI：
10.1021/jo9716082
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发表时间：
1998
影响因子：
3.6
通讯作者：
S. Buchwald
中科院分区：
文献类型：
--
作者：
Marcus C. Hansen;X. Verdaguer;S. Buchwald
我们最近开发了一种还原内酯的新方法，使用二苯酚钛 (1a)/四丁基氟化铵/氧化铝混合物或二氟化钛 (1b) 作为催化剂，可以轻松获得五元环和六元环内醇； 1 聚甲基氢硅氧烷 (PMHS) 用作化学计量还原剂（方案 1）。各种内酯均以良好至优异的产率还原为相应的内醇。在我们对内酯氢化硅烷化的研究中，我们注意到将内酯转化为相应环醚的最常见方法之一是通过两步程序，包括首先用 DIBAL-H 还原（形成内醇），然后用 Et3SiH/BF3 OEt2 处理。 2a 这两个反应都是在惰性气氛下的低温（-78°C）下发生的。该方法已以几乎未改变的形式应用于许多合成中。 3 该硅烷还原方案也已用于还原通过独立方法制备的乳醇。 4
We recently developed a new method for the reduction of lactones that offers easy access to five-and sixmembered ring lactols using a titanocene diphenoxide (1a)/tetrabutylammonium fluoride/alumina mixture or titanocene difluoride (1b) as the catalyst; 1 polymethylhydrosiloxane (PMHS) was used as the stoichiometric reductant (Scheme 1). A variety of lactones were reduced to the corresponding lactols in good to excellent yields.During our studies of lactone hydrosilylation, we noted that one of the most general ways of transforming a lactone to the corresponding cyclic ether is through a twostep procedure involving initial reduction with DIBAL-H (forming the lactol), followed by treatment with Et3SiH/BF3 ‚OEt2. 2a Both of these reactions occurred at low temperatures (-78 C) under an inert atmosphere. This method has been applied, in nearly unaltered form, in many syntheses. 3 This silane reduction protocol has also been used to reduce lactols prepared via independent methods. 4