Direct reduction of alcohols: Highly chemoselective reducing system for secondary or tertiary alcohols using chlorodiphenylsilane with a catalytic amount of indium trichloride
Direct reduction of alcohols: Highly chemoselective reducing system for secondary or tertiary alcohols using chlorodiphenylsilane with a catalytic amount of indium trichloride
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DOI：
10.1021/jo0158534
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发表时间：
2001-11-16
影响因子：
3.6
通讯作者：
Baba, A
中科院分区：
文献类型：
--
作者：
Yasuda, M;Onishi, Y;Baba, A
描述了在催化量的三氯化铟存在下使用氯二苯基硅烷作为氢化物源直接还原醇。苯甲醇、仲醇和叔醇被有效还原，高产率地得到相应的烷烃。带有伯羟基和仲羟基的化合物仅在仲位点被还原，在用 Bu4NF 处理后得到伯醇。该系统仅对羟基表现出高化学选择性，而不会还原容易被标准还原系统还原的其他官能团。因此，对 LiAlH4 或 Zn/H+ 敏感的带有酯、氯、溴或硝基的醇，仅在羟基位点被氯二苯基硅烷/InCl3 系统选择性还原。核磁共振研究揭示了反应过程。首先形成氢化二苯基甲硅烷基醚，然后与充当路易斯酸的 InCl3 形成氧鎓。络合物，通过将氢提供给碳来加速脱硅氧基化。
The direct reduction of alcohols using chlorodiphenylsilane as a hydride source in the presence of a catalytic amount of indium trichloride is described. Benzylic alcohols, secondary alcohols, and tertiary alcohols were effectively reduced to give the corresponding alkanes in high yields. A compound bearing both primary and secondary hydroxyl groups was reduced only at the secondary site to afford the primary alcohol after workup with Bu4NF. This system showed high chemoselectivity only for the hydroxyl group while not reducing other functional groups that are readily reduced by standard reducing systems. Thus alcohols bearing ester, chloro, bromo, or nitro groups, which are sensitive to LiAlH4 or Zn/H+, were selectively reduced only at the hydroxyl sites by the chlorodiphenylsilane/InCl3 system. NMR studies revealed the reaction course. The hydrodiphenylsilyl ether is initially formed and then, with InCl3 acting as a Lewis acid, forms an oxonium. complex, which accelerates the desiloxylation with donation of the hydrogen to the carbon.