Alcohol inversion using cesium carboxylates and DMAP in toluene.
Alcohol inversion using cesium carboxylates and DMAP in toluene.
复制标题
使用羧酸铯和 DMAP 在甲苯中进行酒精转化。
DOI：
10.1021/jo0007783
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发表时间：
2000
期刊：
影响因子：
--
通讯作者：
Snider,BB
中科院分区：
文献类型：
--
作者：
Hawryluk,NA;Snider,BB
在DMF中，通过羧酸铯与仲磺酸的SN2反应转化仲醇已被广泛应用于合成。1，2由于DMF的去除可能很困难，因此使用苯或甲苯作为溶剂和0.5当量的18-冠-6来增溶羧酸钾和铯的替代方法也得到了广泛的应用。3在我们合成双环戊二烯的过程中，4我们发现CsOAc(5当量)与粗硝基苯磺酸盐1在甲苯中回流反应12 h，在没有18-冠-6.4的情况下得到75−85%的2。令人惊讶的是，在同样的条件下，与纯1不发生反应。由于1是由乙醇在CH2Cl2中与硝基苯磺酰氯、乙酸乙酯和二甲基亚胺在CH2Cl2中合成的，我们推测粗品1中残留的DMAP是在甲苯中与CsOAc回流反应所必需的。将CsOAc(5当量)悬浮液在纯Nosyate 1(0.13 M)和DMAP(0.1当量)的甲苯溶液中回流8h，得到85%的醋酸盐2，证实了这一点。
Inversion of secondary alcohols by the SN2 reaction of a cesium carboxylate with a secondary sulfonate in DMF has been widely used in synthesis. 1, 2 Because removal of DMF can be difficult, alternate procedures using benzene or toluene as the solvent with 0.5 equiv of 18-crown-6 to solubilize potassium and cesium carboxylates have also been extensively used. 3 During our synthesis of dysiherbaine, 4 we found that that the SN2 reaction of CsOAc (5 equiv) with crude nitrobenzenesulfonate 1 proceeded cleanly in toluene at reflux for 12 h to give 75− 85% of 2 without the use of 18-crown-6.4 Surprisingly, no reaction occurred under the same conditions with pure 1. Since 1 was prepared from the alcohol with nitrobenzenesulfonyl chloride, Et3N, and DMAP in CH2Cl2, we suspected that residual DMAP present in crude 1 was necessary for the SN2 reaction with CsOAc in toluene at reflux. This was confirmed by heating a suspension of CsOAc (5 equiv) in a toluene solution of pure nosylate 1 (0.13 M) and DMAP (0.1 equiv) at reflux for 8 h to give 85% of acetate 2.