Cationic palladium(II)-catalyzed dehydrative nucleophilic substitutions of benzhydryl alcohols with electron-deficient benzenethiols in water
Cationic palladium(II)-catalyzed dehydrative nucleophilic substitutions of benzhydryl alcohols with electron-deficient benzenethiols in water
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DOI：
10.1039/c6ob01140c
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发表时间：
2016-01-01
影响因子：
3.2
通讯作者：
Azumaya, Isao
中科院分区：
文献类型：
--
作者：
Hikawa, Hidemasa;Machino, Yumo;Azumaya, Isao
报道了用阳离子Pd（II）催化剂作为水中路易斯酸，苯并羟基醇与缺电子苯乙醇的直接亲核取代反应。原子经济和环境友好的方案提供了中等至优异产量的s -苯基化产品。市售的Pd(MeCN)(4)(OTf)(2)、PdCl2(MeCN)(2)和Na2PdCl4是高效催化剂。值得注意的是，这个简单的方案可以在没有任何其他添加剂，如酸，碱或外部配体的情况下实现。用不同取代苯甲醇进行s -苄基化反应速率常数的Hammett研究结果为负。值，表明在过渡态中存在正电荷的积累。
An efficient direct nucleophilic substitution of benzhydryl alcohols with electron-deficient benzenethiols using cationic Pd(II) catalysts as Lewis acids in water is reported. Atom economical and environmentally benign protocols afford S-benzylated products in moderate to excellent yields. Commercially available Pd(MeCN)(4)(OTf)(2), PdCl2(MeCN)(2), and Na2PdCl4 are highly efficient catalysts. Notably, this simple protocol can be achieved without any other additives such as acids, bases, or external ligands. A Hammett study on the rate constants of S-benzylation by using various substituted benzhydryl alcohols yielded negative. values, suggesting that there is a build-up of positive charge in the transition state.