Facile and Selective Cleavageof Allyl Ethers Based on Palladium(0)-Catalyzed Allylic Alkylationof<i>N</i>,<i>N</i>′-DimethylbarbituricAcid
作者:Hirokazu Tsukamoto、Yoshinori Kondo
DOI:10.1055/s-2003-39320
日期:——
The classical palladium(0)-catalyzed allylic alkylation of N,N'-dimethylbarbituric acid can be applied to the facile and selective cleavage of allylic alkyl ethers to release the corresponding alcohols in excellent yield.This reaction proceeds under neutral conditions without any additive to activate the allyl ethers and tolerates various functional groups, such as ester, ether, ketone, alkyl and aryl
A mild and efficient selective tetrahydropyranylation of primary alcohols and deprotection of THP ethers of phenols and alcohols using PdCl2(CH3CN)2 as catalyst
作者:Yan-Guang Wang、Xiao-Xing Wu、Zhi-Yong Jiang
DOI:10.1016/j.tetlet.2004.02.057
日期:2004.3
Primary alcohols were selectively tetrahydropyranylated in good to excellent yields at room temperature using PdCl2(CH3CN)2 as catalyst in tetrahydrofuran (THF) in the presence of phenols, secondary, and tertiary alcohols. The tetrahydropyranyl (THP) group could be efficiently removed using PdCl2(CH3CN)2 as catalyst in CH3CN, while other protection groups such as p-toluenesulfonyl (Ts), tert-butyldiphenylsilyl
[reaction: see text] Allyl and propargylethers were effectively deallylated or depropargylated to the parent alcohols via a C-O bond cleavage catalyzed by a low-valent titanium reagent (LVT), Ti(O-i-Pr)4/TMSCl/Mg or Ti(O-i-Pr)4/MgBr2/Mg, under mild reaction conditions. Differentiation between the allyl and propargylethers was achieved by the reaction in the presence of AcOEt as an additive. The reagent
Child's play! Allyl ethers as protecting groups for hydroxyl functions can be removed readily with a combination of DIBAL and catalytic amounts of [NiCl2 (dppp)]. Propene is expelled in this remarkably selective reaction, and a nickel-catalyzed hydroalumination-elimination pathway is proposed [Eq. (a)]. dppp=propane-1,3-diylbis(diphenylphosphane).
Deprotection of Tetrahydropyranyl Ethers with Montmorillonite K-10 Clay in Methanol
作者:Takahiko Taniguchi、Kohei Kadota、Adel S. ElAzab、Kunio Ogasawara