- Self-assembled orthoester cryptands: Orthoester scope, post-functionalization, kinetic locking and tunable degradation kinetics
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Dynamic adaptability and biodegradability are key features of functional, 21st century host-guest systems. We have recently discovered a class of tripodal supramolecular hosts, in which two orthoesters act as constitutionally dynamic bridgeheads. Having previously demonstrated the adaptive nature of these hosts, we now report the synthesis and characterization-including eight solid state structures-of a diverse set of orthoester cages, which provides evidence for the broad scope of this new host class. With the same set of compounds, we demonstrated that the rates of orthoester exchange and hydrolysis can be tuned over a remarkably wide range, from rapid hydrolysis at pH 8 to nearly inert at pH 1, and that the Taft parameter of the orthoester substituent allows an adequate prediction of the reaction kinetics. Moreover, the synthesis of an alkyne-capped cryptand enabled the post-functionalization of orthoester cryptands by Sonogashira and CuAAC "click" reactions. The methylation of the resulting triazole furnished a cryptate that was kinetically inert towards orthoester exchange and hydrolysis at pH > 1, which is equivalent to the "turnoff" of constitutionally dynamic imines by means of reduction. These findings indicate that orthoester cages may be more broadly useful than anticipated, e.g. as drug delivery agents with precisely tunable biodegradability or, thanks to the kinetic locking strategy, as ion sensors.
- L?w, Henrik,Mena-Osteritz, Elena,Von Delius, Max
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p. 4785 - 4793
(2018/06/07)
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- Heterobimetallic dinuclear lanthanide alkoxide complexes as acid-base difunctional catalysts for transesterification
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A practical lanthanide(III)-catalyzed transesterification of carboxylic esters, weakly reactive carbonates, and much less-reactive ethyl silicate with primary and secondary alcohols was developed. Heterobimetallic dinuclear lanthanide alkoxide complexes [Ln2Na8{(OCH2CH2NMe2)}12(OH)2] (Ln = Nd (I), Sm (II), and Yb (III)) were used as highly active catalysts for this reaction. The mild reaction conditions enabled the transesterification of various substrates to proceed in good to high yield. Efficient activation of transesterification may be endowed by the above complexes as cooperative acid-base difunctional catalysts, which is proposed to be responsible for the higher reactivity in comparison with simple acid/base catalysts.
- Zeng, Ruijie,Sheng, Hongting,Zhang, Yongcang,Feng, Yan,Chen, Zhi,Wang, Junfeng,Chen, Man,Zhu, Manzhou,Guo, Qingxiang
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p. 9246 - 9252
(2014/12/11)
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- Method of Synthesizing Polyol Acetate by Using Catalyst of Ionic Liquid Heteropoly Acid
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The present invention uses a nitrogen-containing organic compound to be reacted with an alkyl sultone to obtain a zwitterion compound. The zwitterion compound is reacted with a heteropoly acid (HPA) to obtain an ionic liquid HPA (IL-HPA). The IL-HPA is used for acetylation of polyol and HOAc for obtaining polyol acetate. The IL used in the reaction can be recycled. Thus, problems of product separation, waste acid handling, and corrosion of facilities are solved and production through esterification is improved with a green catalysis.
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Paragraph [0032]; [0039]
(2013/05/09)
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- Synthesis of Sterically Hindered Secondary Aminoether Alcohols
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Severely sterically hindered secondary aminoether alcohols are prepared by reacting an organic carboxylic acid or alkali metal salt of an organic carboxylic acid with a sulfonyl halide, a sulfuryl halide, a mixed sulfuryl ester halide or a mixed sulfuryl amide halide to yield a sulfonic-carboxylic anhydride compound which is then reacted with a dioxane to cleave the ring of the dioxane, yielding a cleavage product which cleavage product is then aminated with an alkylamine and hydrolyzed with base to yield the severely sterically hindered secondary aminoether alcohol.
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Page/Page column 6
(2010/11/28)
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- SYNTHESIS OF SEVERELY STERICALLY HINDERED SECONDARY AMINOETHER ALCOHOLS FROM A KETENE AND/OR CARBOXYLIC ACID HALIDE AND/OR CARBOXYLIC ACID ANHYDRIDE
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Severely sterically hindered secondary aminoether alcohols are prepared by a process comprising reacting a ketene with sulfuric acid to produce an anhydride which is then reacted with, to cleave the ring of, a dioxane to yield a cleavage product which is then aminated using an amine, followed by hydrolysis with a base to yield the desired severely sterically hindered secondary aminoether alcohol.
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Page/Page column 19-20
(2008/06/13)
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- P2O5 / SiO2 as a mild and efficient reagent for acylation of alcohols, phenols and amines under solvent-free conditions
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P2O5 / SiO2 is a highly efficient reagent for the acetylations of a variety of alcohols, phenols and amines with acetic anhydride under solvent-free conditions. Primary, secondary, allylic and benzylic alcohols, diols and phenols with electron-donating or withdrawing substituents can be easily acetylated in good to excellent yield.
- Eshghi, Hossein,Shafieyoon, Parvaneh
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p. 802 - 805
(2007/10/03)
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- Indium triflate: An efficient catalyst for acylation reactions
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Indium triflate is shown to be an extremely efficient catalyst for the acylation of alcohols and amines.
- Chauhan, Kamlesh K.,Frost, Christopher G.,Love, Ian,Waite, David
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p. 1743 - 1744
(2007/10/03)
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- A One-step and Chemoselective Conversion of Silyl-protected Alcohols into the Corresponding Acetates
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A reagent system of acetyl bromide combined with a catalytic amount of tin(II) bromide cleaves readily trialkylsilyl ethers to give the corresponding acetates in high yields under very mild conditions.
- Oriyama, Takeshi,Oda, Mihoko,Gono, Junko,Koga, Gen
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p. 2027 - 2030
(2007/10/02)
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- THE SOLUBILITY OF CARBON DIOXIDE IN SOME ACETIC ACID ESTERS
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The absorption of carbon dioxide in organic solvents containing acetyl groups (ethylene glycol diacetate, diethylene glycol diacetate, triethylene glycol diacetate, propylene glycol diacetate, ethyl cellosolve acetate, 1,4-butanediol diacetate, glycerol triacetate and β-phenyl acetate) is studied. Bunsen absorption coefficients in the range of 5 to 50 atm and at 25 deg C are obtained. Some considerations about the correlation between absorptive capacity and the molecular structure of these organic compounds are presented.
- Vilcu, Rodica,Gainar, Ion,Maior, Ovidiu,Anitescu, Gheorghe
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p. 875 - 878
(2007/10/03)
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- Acetyl transfer reactions on AlPO4-Al2O3
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An efficient acetylation of alcohols and aliphatic amines promoted by the AlPO4-Al2O3/ethyl acetate system is described.The solid catalist acts, at least in part, as the acetyl carrier.
- Costa, Antonio,Riego, Juan Martin
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p. 2327 - 2328
(2007/10/02)
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