A wide variety of alcohols, phenols and amines are efficiently and selectively converted into the corresponding acetates by treatment with acetic anhydride in the presence of catalytic amounts of La(NO3)3·6H2O undersolvent-freeconditions at room temperature. The method is compatible with acid sensitive hydroxyl protecting groups such as TBDMS, THP, OBz, OBn, Boc and some isopropylidenes and offers
A simple and efficient protocol for the selectivedeprotection of t-butyldimethylsilyl (TBDMS) ethers using 20 mol% ZrCl4 in 20–45 min and in high yields, is reported, wherein it is demonstrated that acid and base sensitive groups and allylic and benzylic groups are unaffected.
Copper(II) bromide as efficient catalyst for silyl- to bisarylmethyl ethers interconversion (transprotection)
作者:Simon Specklin、Florian Gallier、Rofia Mezaache、Hassina Harkat、Yénimégué Albert Dembelé、Jean-Marc Weibel、Aurélien Blanc、Patrick Pale
DOI:10.1016/j.tetlet.2011.08.148
日期:2011.11
Primary and secondary silylated alcohols are easily converted to bis(methoxyphenyl)methyl (BMPM) ethers in good yields using CuBr2 as catalyst in acetonitrile at room temperature. Various other protecting groups are compatible with this mild and convenient process. (C) 2011 Elsevier Ltd. All rights reserved.
Nucleophilic Acyl Substitutions of Anhydrides with Protic Nucleophiles Catalyzed by Amphoteric, Oxomolybdenum Species
作者:Chien-Tien Chen、Jen-Huang Kuo、Vijay D. Pawar、Yogesh S. Munot、Shieu-Shien Weng、Cheng-Hsiu Ku、Cheng-Yuan Liu
DOI:10.1021/jo048363v
日期:2005.2.1
[GRAPHICS]Among six different group VIb oxometallic species examined, dioxomolybdenum dichloride and oxomolybdenum tetrachloride were the most efficient catalysts to facilitate nucleophilic acyl substitution (NAS) of anhydrides with a myriad array of alcohols, amines, and thiols in high yields and high chemoselectivity. In contrast to the well-recognized redox chemical behaviors associated with oxomolybdenum(VI) species, the catalytic NAS was unprecedented and tolerates virtually all kinds of functional groups. By using benzoic anhydride as a mediator for in situ generation of an incipient mixed anhydride -MoO2Cl2 adduct with a given functional alkanoic acid, one can achieve oleate, dipeptide, diphenylmethyl, N-Fmoc-alpha-amino, pyruvic, and tert-butylthio ester, N-tert-butylamide, and trityl methacrylate syntheses with appropriate protic nucleophiles. The amphoteric character of the Mo=O unit in oxomolybdenum chlorides was found to be responsible for the catalytic NAS profile as supported by a control NAS reaction of using an authentic adduct-MoOCl2(O-2-CBut)(2) between pivalic anhydride and MoO2Cl2 as the catalyst.