- Phase separation and coalescence, annihilation of liquid crystal textures during polymerization of main-chain liquid crystalline polyesters
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Using a novel thin film polymerization technique, we have observed the phase separation, coalescence, and annihilation of liquid crystal textures during polymerization of wholly aromatic main-chain liquid crystalline polymer poly(p-oxybenzoate/2,6-oxynaphthoate) (P(OBA/ONA)). The polycondensation reaction was conducted and observed in situ on the heating stage of a polarizing microscope. After the melting of monomers, the reaction system started from a homogeneous phase and then changed into a heterogeneous one. The following morphological changes during the entire reaction were observed: generation of anisotropic phase, coalescence of liquid crystal domains, formation of schlieren texture, annihilation of disclinations, and formation of stripe texture. We found all the liquid crystal domains formed in the isotropic melt during the early stage of our polymerization reactions had the disclination strength of +1. The number of defects decreased with increasing reaction time through coalescence and annihilation. At the early stage of polymerization, the dominant factor affecting annihilation rate was the viscosity characteristics at elevated temperatures.
- Cheng, Si-Xue,Chung, Tai-Shung
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- The first vinyl acetate mediated organocatalytic transesterification of phenols: A step towards sustainability
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The present report outlines our efforts toward a simple yet elegant protocol for O-acylation of a wide variety of phenols. This highly enabling and solventless method relies on vinyl acetate as an innocuous acyl donor and DABCO as an organocatalyst. Operational simplicity, excellent yields, higher and faster conversion rates without excess reagents, a simple workup and essentially no need of columns are some of the salient features of the reported protocol.
- Kumar, Manoj,Bagchi, Sourav,Sharma, Anuj
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supporting information
p. 8329 - 8336
(2015/11/10)
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- Facile catalyzed acylation of alcohols, phenols, amines and thiols based on ZrOCl2·8H2O and acetyl chloride in solution and in solvent-free conditions
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Acylation of heteroatoms (O, N and S) with acetyl chloride based on the use of a catalytic amount of the moisture stable, inexpensive ZrOCl 2?8H2O, proceeds efficiently producing the corresponding acylated products in excellent yields.
- Ghosh, Rina,Maiti, Swarupananda,Chakraborty, Arijit
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p. 147 - 151
(2007/10/03)
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- Facile catalyzed acylation of heteroatoms using BiCl3 generated in situ from the procatalyst BiOCl and acetyl chloride
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Acylation of a variety of alcohols, phenols, aliphatic and aromatic amines, a thiol and a thiophenol proceeds efficiently using BiCl3 generated in situ from the procatalyst BiOCl and acetyl chloride in a solvent or under solventless conditions, furnishing the corresponding acylated derivatives in very good to excellent yields.
- Ghosh, Rina,Maiti, Swarupananda,Chakraborty, Arijit
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p. 6775 - 6778
(2007/10/03)
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- Regioselective hydrolysis of diacetoxynaphthalenes catalyzed by Pseudomonas sp. lipase in an organic solvent
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Depending on the relative positions of the acetyl groups in the aromatic rings, the Pseudomonas sp. lipase-catalyzed hydrolysis of diacetoxynaphthalenes in tert-butylmethyl ether proceeds regioselectively to afford the corresponding monoacetates.
- Ciuffreda, Pierangela,Casati, Silvana,Santaniello, Enzo
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p. 317 - 321
(2007/10/03)
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- Lipase catalyzed acylation of phenols in organic solvents
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Chromobacterium viscosum lipase, adsorbed on Celite, catalyzes the esterification of phenols in organic medium using vinyl acetate as acylating agent.
- Lambusta, Daniela,Nicolosi, Giovanni,Piattelli, Mario,Sanfilippo, Claudia
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- Process for oxidizing 2,6-diisopropylnaphthalene
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In a process for producing 2,6-dihydroxynaphthalene from 2,6-diisopropylnaphthalene, 2,6-diisopropylnaphthalene is oxidized in the presence of a specific proportion of a basic compound to hydroxylate or hydroperoxylate 2,6-diisopropylnaphthalene in a high conversion, and the resulting intermediate is then subjected to acid cleavage in the presence of hydrogen peroxide to produce 2,6-dihydroxynaphthalene in a high yield. The yield of 2,6-dihydroxynaphthalene increases by subjecting the reaction mixture containing the above intermediate to a purifying operation or dehydrating operation or adding acetone to it before it is submitted to the acid cleavage. 2,6-Dihydroxynaphthalene may be reacted with acetic anhydride to obtain 2,6-diacetoxynaphthalene.
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- Process for producing 2,6-dihydroxynaphthalene and 2,6-diacetoxynaphthalene
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Disclosed herein is a process for producing 2,6-dihydroxynaphthalene which comprises oxidizing 2,6-di(2-hydroxy-2-propyl)naphthalene in acetonitrile, 1,4-dioxane or a mixture thereof with hydrogen peroxide in the presence of an inorganic acid or a solid acid at a temperture in the range of room temperature to the boiling point of the solution of the 2,6-di(2-hydroxy-2-propyl)naphthalene in acetonitrile or 1,4-dioxane, the acetonitrile, 1,4-dioxane or a mixture thereof being used in an amount of 3 to 30 ml to one gram of the 2,6-di(2-hydroxy-2-propyl)naphthalene.
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- Method for producing 2,6-diacetoxynaphthalene
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2,6-Diacetoxynaphthalene (DAN) is produced by subjecting 6-acetoxy-2-acetonaphthone (AAN) to a Baeyer-Villiger oxidation using a peroxy compound, e.g., peracetic acid, as oxidant under conditions such that the reaction mass contains no more than about 0.1 wt.% of a mineral acid based on the weight of the initially added pure peroxy compound. The AAN is preferably produced by subjecting 2-naphthyl acetate to a Fries rearrangement or 2-naphthol to a Friedel-Crafts acetylation, to produce 6-hydroxy-2-acetonaphthone (HAN), e.g., using hydrogen fluoride as catalyst, and acetylating the HAN, e.g., with acetic anhydride.
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