化学
重氮甲烷
二异丙基氨基锂
芳基
烷基
去甲基化
药物化学
亚甲基
硅烷化
位阻效应
酰胺
碱金属
有机化学
酰胺锂
四甲基铵
脱质子化
催化作用
离子
生物化学
基因表达
DNA甲基化
基因
对映选择合成
作者
Jih Ru Hwu,Fung Fuh Wong,Jow Lay Huang,Shwu‐Chen Tsay
摘要
Removal of methyl, benzyl, and methylene groups from alkyl aryl ethers is among the most popular deprotecting methods in organic synthesis. Alkali organoamides NaN(SiMe3)2 and LiN(i-Pr)2, often used as organic bases, have been developed as efficient deprotecting agents. Treatment of aryl methyl ethers with 1.5 equiv of NaN(SiMe3)2 or LiN(i-Pr)2 in THF and 1,3-dimethyl-2-imidazolidinone in a sealed tube at 185 °C produced the corresponding phenol derivatives in good to excellent yields (80−97%). Removal of the methylene unit from benzodioxole derivatives was also accomplished by use of 2.5 equiv of these alkali organoamides. The corresponding catechols were obtained in 93−99% yields. The activity of NaN(SiMe3)2 was proven lower than that of LiN(i-Pr)2; it is due to the steric congestion and the α-stabilizing effect of the silyl groups. Thus selective mono-O-demethylation of o-dimethoxybenzenes can be achieved by the use of NaN(SiMe3)2 but not LiN(i-Pr)2. O-Debenzylation of aryl benzyl ethers, however, can be accomplished by the use of LiN(i-Pr)2.
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