- Separation, recovery and reuse of N-heterocyclic carbene catalysts in transesterification reactions
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A novel and convenient strategy to separate, recover and reuse N-heterocyclic carbene catalysts in transesterification reactions has been developed.
- Zeng, Tieqiang,Song, Gonghua,Li, Chao-Jun
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- Tetraethylammonium hydrogen carbonate: A cheap, efficient, and recyclable catalyst for transesterification reactions under solvent-free conditions
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Tetraethylammonium hydrogen carbonate (TEAHC) was proven to be an efficient catalyst for transesterification reactions in the absence of solvent. The reaction between isopropenyl or ethyl acetate and an alcohol (not efficient in the absence of catalyst) was induced by the presence of TEAHC, which seems to assist the proton transfer from the alcohol to the ester, yielding the corresponding acetate in very good yields in the absence of any solvent. Moreover, the TEAHC can be recycled several times without significant loss in activity.
- Chiarotto, Isabella
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- A novel silver nanoparticle embedded mesoporous polyaniline (mPANI/Ag) nanocomposite as a recyclable catalyst in the acylation of amines and alcohols under solvent free conditions
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A mesoporous polyaniline/silver (mPANI/Ag) nanocomposite has been prepared using mesoporous organic polymer polyaniline with silver nitrate via radical polymerization of aniline monomer in the presence of hydrochloric acid. The mPANI/Ag nanocomposite has been characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectra (EDX), Fourier transform infrared spectroscopy (FT-IR), and ultraviolet-visible absorption spectra (UV-vis). The XRD patterns indicated that the crystalline phase of Ag is cubic. TEM images show that the Ag nanoparticles are well dispersed in the mesoporous polyaniline matrix. The mPANI/Ag acts as an efficient heterogeneous nanocatalyst in the acylation of substituted amines and alcohols using acetic acid. The catalyst is air-stable, inexpensive, easy to prepare and can be reused several times without a significant decrease in activity and selectivity. This journal is
- Mandi, Usha,Roy, Anupam Singha,Banerjee, Biplab,Islam, Sk. Manirul
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p. 42670 - 42681
(2015/02/19)
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- Electrogenerated N-heterocyclic carbenes in the room temperature parent ionic liquid as an efficient medium for transesterification/acylation reactions
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N-Heterocyclic carbenes (NHCs), generated by electrochemical reduction under galvanostatic control of 1,3-dialkylimidazolium-based ionic liquids, were employed as catalysts in transesterification reactions in the parent, room temperature ionic liquids (RTILs) as solvents, without the utilisation of any volatile organic solvent or base. The reaction between isopropenyl or ethyl acetate and an alcohol (not efficient in the absence of catalyst) was induced by the presence of an electrogenerated NHC, which seems to assist the proton transfer from the alcohol to the ester, yielding the corresponding acetate. The reaction also proceeds with methyl nicotinate as starting ester and 2-(diethylamino)ethanol or benzyl alcohol as alcohols and leads to the corresponding biologically active compounds, nicametate and benzyl nicotinate, in good yields. All products were isolated in good to excellent yields and complete recyclability of the ionic liquid as solvent has been demonstrated.
- Chiarotto, Isabella,Feroci, Marta,Sotgiu, Giovanni,Inesi, Achille
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supporting information
p. 326 - 331
(2013/02/25)
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- Polymer-supported gadolinium triflate as a convenient and efficient Lewis acid catalyst for acetylation of alcohols and phenols
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A polymer-supported gadolinium triflate (CMPS-IM-Gd) catalyst was prepared from chloromethyl polystyrene (CMPS) resin using a simple and convenient procedure. This polymeric catalyst was used as an efficient Lewis acid catalyst for the acetylation of various alcohols and phenols with acetic anhydride, affording high yields under mild conditions. The reaction was completed in a short period of time with small amounts of the catalyst. The catalyst was reused over 10 times without any significant loss of its catalytic activity.
- Yoon, Hyo-Jin,Lee, Sang-Myung,Kim, Jong-Ho,Cho, Hong-Jun,Choi, Jung-Woo,Lee, Sang-Hyeup,Lee, Yoon-Sik
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p. 3165 - 3171
(2008/09/20)
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- The p-(Methylsulfinyl)benzyl Group: A TFA-Stable Carboxyl-Protecting Group Readily Convertible to a TFA-Labile Group
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The p-(methylsulfinyl)benzyl or Msib ester is recommended as a selectively cleavable carboxyl-protecting group for peptide synthesis.Peptide oramino acid esters of p-(methylsulfinyl)benzyl alcohol, HO-Msib (2), or p-(methylthio)benzyl alcohol, HO-Mtb (1), are readily prepared from the corresponding alcohols or alkyl halides.Msib esters may also be obtained from Mtb esters by oxidation with m-chloroperbenzoic acid.Msib esters are readily deoxygenated by excess Me3SiCl/Ph3P, Me3SiCl/Me2S, or anhydrous hydrogen chloride.Msib esters are exceedingly stable to TFA while Mtb esters solvolyze rapidly.A sample peptide synthesis demonstrates the protection of the C-terminal carboxyl group during synthesis as the Msib ester followed by Msib group removal on completion of synthesis by deoxygenation and TFA solvolysis.The stability of Mtb and Msib esters to typical acid conditions of peptide synthesis is described.The stability of Msib esters to various peptide synthesis conditions suggests that the Msib group should be quite useful as a carboxyl-protecting group in peptide synthesis.
- Samanen, James M.,Brandeis, Ester
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p. 561 - 569
(2007/10/02)
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