- KMnO4-catalyzed chemoselective deprotection of acetate and controllable deacetylation-oxidation in one pot
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A novel and efficient protocol for chemoselective deacetylation under ambient conditions was developed using catalytic KMnO4. The stoichiometric use of KMnO4 highlighted the dual role of a heterogeneous oxidant enabling direct access to aromatic aldehydes in one-pot sequential deacetylation-oxidation. The reaction employed an alternative solvent system and allowed the clean transformation of benzyl acetate to sensitive aldehyde in a single step while preventing over-oxidation to acids. Use of inexpensive and readily accessible KMnO4 as an environmentally benign reagent and the ease of the reaction operation were particularly attractive, and enabled the controlled oxidation and facile cleavage of acetate in a preceding step. This journal is
- Gurawa, Aakanksha,Kumar, Manoj,Rao, Dodla S.,Kashyap, Sudhir
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supporting information
p. 16702 - 16707
(2020/10/27)
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- Investigation of steapsin lipase for kinetic resolution of secondary alcohols and synthesis of valuable acetates in non-aqueous reaction medium
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In present study, the application of steapsin lipase (as a biocatalyst) was investigated for kinetic resolution of secondary alcohols (1-phenyl ethanol and their derivatives) using vinyl acetate as an activated acyl donor. The enzymatic protocol was optimized for various reaction parameters such as effect of the molar ratio, solvent, temperature, time and biocatalyst loading to obtain best reaction conditions. On optimization, developed enzymatic methodology provided considerable enantiomeric excess of the product (up to 92% ee) at 55 °C in n-hexane as a solvent. Furthermore using the developed protocol, synthesis of several industrially important acetates was successfully achieved with excellent yield (up to 99%). During acetate synthesis, the biocatalyst was remarkably reused for eight consecutive recycles without any significant loss in its catalytic activity. This revealed the good potential of steapsin lipase for application in organic solvents.
- Dhake, Kishor P.,Deshmukh, Krishna M.,Wagh, Yogesh S.,Singhal, Rekha S.,Bhanage, Bhalchandra M.
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experimental part
p. 15 - 23
(2012/06/29)
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- Silica-bonded N-propyl sulfamic acid as an efficient catalyst for the formylation and acetylation of alcohols and amines under heterogeneous conditions
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A simple and efficient procedure for the preparation of silica-bonded N-propyl sulfamic acid (SBNPSA) by the reaction of 3-aminopropylsilica (1) and chlorosulfonic acid in chloroform is described. This solid acid is employed as a new catalyst for the formylation of alcohols and amines with ethyl formate under mild and heterogeneous conditions at room temperature with good to excellent yields. Also, SBNPSA catalyzed acetylation of various alcohols and amines with acetic anhydride at room temperature.
- Niknam, Khodabakhsh,Saberi, Dariush
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experimental part
p. 5210 - 5214
(2009/12/06)
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- Thallium(III) chloride: A mild and efficient catalyst for acylation of alcohols, phenols and thiols, and for geminal diacylation of aldehydes under solvent-free conditions
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Thallium(III) chloride is a simple and efficient catalyst for acylation of alcohols, phenols and thiols. It is also very effective for geminal diacylation of aldehydes. The acylation reaction using acetic anhydride proceeds in excellent yield in the presence of catalytic amounts of thallium(III) chloride (1 mol%) at room temperature within relatively short reaction times (20 min). Structurally diverse alcohols, phenols, thiols and aldehydes undergo acylation under solvent-free conditions.
- Kadam, Santosh T.,Kim, Sung Soo
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experimental part
p. 3307 - 3313
(2009/05/07)
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- Thio-substituted tricyclic and bicyclic aromatic methanesulfinyl derivatives
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The present invention is related to chemical compositions, processes for the preparation thereof and uses of the composition. Particularly, the present invention relates to compositions of compounds of Formula (A): wherein Ar, Y, R1 and q are as defined herein; and their use in the treatment of diseases, including treatment of sleepiness, promotion of wakefulness, treatment of Parkinson's disease, cerebral ischemia, stroke, sleep apneas, eating disorders, stimulation of appetite and weight gain, treatment of attention deficit hyperactivity disorder ("ADHD"), enhancing function in disorders associated with hypofunctionality of the cerebral cortex, including, but not limited to, depression, schizophrenia, fatigue, in particular, fatigue associated with neurologic disease, such as multiple sclerosis, chronic fatigue syndrome, and improvement of cognitive dysfunction.
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Page/Page column 30
(2008/06/13)
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- A Concise, High Yield Synthesis of the Selective ECE-Inhibitor, CGS 35066
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A highly efficient synthesis of the selective endothelin-converting enzyme, CGS 35066 is described. The key steps involved a Pd-catalyzed coupling of the phenyl rings of a diphenyl ether, and the use of the Schoellkopf reagent, (2R)-2-isopropyl-3,6-dimethoxy-2,5-dihydropyrazine as a chiral auxiliary furnishing a dibenzofuranylmethyl substituted amino ester in high (>98%) enantiomeric purity, which was then carried forward to complete the synthesis of the ECE inhibitor CGS 35066.
- Fauq, Abdul H.,Khan, Murad A.,Eckman, Christopher
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p. 775 - 782
(2007/10/03)
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- Synthesis of m-phenoxybenzaldehyde starting from chlorobenzene and m-cresol: Some aspects of process development
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m-Phenoxybenzaldehyde (MPB) is an important intermediate for synthetic pyrethroids. In the present paper, an economic process scheme was developed to synthesize MPB starting from cheaper reactants. The process scheme was started with the synthesis of m-phenoxytoluene (MPT). Oxidation of MPT by air gave MPB, but the selectivity was found to be high at low conversions of about 10%, and if the conversion level was increased, then large amounts of the undesired m-phenoxybenzoic acid (MPBA) was formed. To obtain the desired aldehyde, Rosenmund reduction of MPBA was carried out to give high yields of the MPB. The effects of different parameters such as catalyst, substrate concentration, temperature, etc., were studied for all three of the reactions, viz., Ullmann ether synthesis, oxidation, and Rosenmund reduction. MPT was prepared from chlorobenzene, a relatively cheaper starting material, in the presence of polyethylene glycol) as cosolvent and cuprous chloride as the catalyst. A selectivity of 97% was obtained with 86% conversion to the product. Oxidation of MPT was carried out by air in the presence of cobalt acetate as catalyst and sodium bromide as catalyst promoter. The selectivity with respect to the aldehyde and the ester was 37.4 and 30.6%, respectively, at a restricted overall conversion of 24%. The process parameters were controlled to achieve high selectivity towards the aldehyde. The acid, formed as the side product, was reduced to the aldehyde by Rosenmund reduction via the acyl chloride. At a conversion level of 85%, a selectivity of 87% to MPB was obtained using Pd/C.
- Chandnani, Kavita H.,Chandalia, Sampatraj B.
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p. 416 - 424
(2013/09/08)
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- Benzylic Bromination-Acetoxylation of Toluenes by Bromide Ion Catalyzed Thermal Decomposition of Peroxydisulfate in Acetic Acid in the Presence of Acetate Ions
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Side-chain bromination and acetoxylation of alkylaromatics by halide ion induced decomposition of potassium peroxydisulfate in acetic acid have been studied by product analysis techniques.Catalytic amounts of lithium bromide in the presence of sodium acetate were found effective in promoting benzylic bromination, followed by conversion to the corresponding benzyl acetates by reaction with acetate.The reaction is interpreted to take place by the redox and free-radical chain mechanism involving bromine atoms (ρ = -1.38 vs. ? + for substituted toluenes).In competiti ve experiments, benzyl and 4-nitrobenzyl acetates were found lees reactive than the corresponding toluenes in acetic acid with the couple S2O82-/Br- but more reactive in carbon tetrachloride with N-bromosuccinimide.
- Citterio, Attilio,Santi, Roberto,Pagani, Anselmo
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p. 4925 - 4927
(2007/10/02)
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- Process for the preparation of diphenyl ether derivatives
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The invention relates to a process for the preparation of compounds of formula (I) STR1 wherein R1 stands for hydrogen or the group COR2, wherein R2 stands for a straight or branched chained alkyl having 1 to 8 carbon atoms optionally substituted with phenyl, naphthyl, tetrahydronaphthyl or m-phenoxy-benzyl, cycloalkyl having 3 to 6 carbon atoms optionally substituted with one or more straight or branched chained alkyl or alkenyl having 1 to 6 carbon atoms, phenyl or naphthyl. The compounds of formula (I) are prepared according to the invention by (a) reacting esters of formula (II) STR2 wherein X stands for chlorine or bromine and R2 has the same meanings as defined above with a phenol alkali metal salt and (b) if desired converting the diphenyl ethers so obtained to a specific compound of formula (I), m-phenoxybenzyl alcohol by the hydrolysis of the ester group.
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- Bromination of side chain of m-phenoxytoluene
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A process for brominating m-phenoxytoluene with a polyhaloethane having the formula STR1 wherein W and Z respectively represent Cl or Br and X and Y respectively represent Cl, Br or H in a liquid phase.
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