- Free-radical chain generation of ketene during the synthesis of liquid crystalline aromatic polyesters
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At the high temperatures used for the preparation of liquid crystalline aromatic polyesters (LCPs), ketene cleavage occurred from acetoxyarenes. Ketene is known to oligomerize to colored oligomers which may be responsible for an undesirable yellow color i
- Stuparu, Mihaiela C.,Xu, Juhua,Hall Jr.
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Read Online
- Aerobic oxidative cleavage and esterification of C[dbnd]C bonds catalyzed by iron-based nanocatalyst
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Functionalization of C[dbnd]C bonds by oxidative cleavage plays an important role in organic synthesis. However, the traditional functionalized products are mainly aldehydes, ketones and carboxylic acids, and the substrates are limited to examples of active aromatic olefins with very scarce inactive olefins. Herein we disclose an efficient protocol for the direct formation of esters by oxidative cleavage of C[dbnd]C bonds using heterogeneous iron nanocomposite catalyst supported on nitrogen-doped carbon materials with molecular oxygen and tert-butylhydroperoxide (TBHP) as the oxidants. The results show that molecular oxygen as the terminal oxidant is mainly responsible for the cleavage process, and that the auxiliary oxidant TBHP promotes the formation of the intermediate epoxide, thus increasing the selectivity of the product. The catalytic system has a wide range of substrate compatibility involving the challenging inactive aliphatic and long-chain alkyl aryl olefins. The catalyst was reused seven times with no loss in catalytic activity. Characterization and control experiments uncover that the core-shell Fe and Fe3C nanoparticles encapsulated by graphitic carbon play a predominant role in catalyzing the oxidative cleavage of olefins to esters. Preliminary mechanistic studies disclose that this process involves both free radical reactions and tandem sequential reactions.
- An, Yue,Fu, Weiru,Tan, Shangzhi,Wang, Lianyue,Yu, Xiangzhu,Zhao, Zhengjia,Zhu, Lina
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- Discovery of new chalone adamantyl arotinoids having RXRα-modulating and anticancer activities
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In the present study, a new series of chalcone adamantly arotinoids (chalcone AdArs) derived from RAR antagonist MX781, are synthesized, characterized, and evaluated for the biological activities in vitro. The studies of antiproliferative activity and RXR
- Ao, Mingtao,Hu, Xianwen,Qian, Yuqing,Li, Boqun,Zhang, Jianyu,Cao, Yin,Zhang, Yuxiang,Guo, Kaiqiang,Qiu, Yingkun,Jiang, Fuquan,Wu, Zhen,Fang, Meijuan
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- 7,10-Dibromo-2,3-dicyanopyrazinophenanthrene Aggregates as a Photosensitizer for Nickel-Catalyzed Aryl Esterification
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Self-assembled aggregates of 7,10-dibromo-2,3-dicyanopyrazinophenanthrene which act as a new organophotocatalyst in combination with Ni catalyst for the C aryl-O acylcross-coupling reactions of carboxylic acids with aryl halides are described. This visible-light-induced C aryl-O acylbond-formation reaction proceeds smoothly to afford aryl esters with satisfactory to excellent yields.
- Bao, Ming,He, Min,Yang, Shilei,Yu, Xiaoqiang
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supporting information
(2021/10/05)
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- Energy-Transfer-Mediated Photocatalysis by a Bioinspired Organic Perylenephotosensitizer HiBRCP
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Energy transfer plays a special role in photocatalysis by utilizing the potential energy of the excited state through indirect excitation, in which a photosensitizer determines the thermodynamic feasibility of the reaction. Bioinspired by the energy-transfer ability of natural product cercosporin, here we developed a green and highly efficient organic photosensitizer HiBRCP (hexaisobutyryl reduced cercosporin) through structural modification of cercosporin. After structural manipulation, its triplet energy was greatly improved, and then, it could markedly promote the efficient geometrical isomerization of alkenes from the E-isomer to the Z-isomer. Moreover, it was also effective for energy-transfer-mediated organometallic catalysis, which allowed realization of the cross-coupling of aryl bromides and carboxylic acids through efficient energy transfer from HiBRCP to nickel complexes. Thus, the study on the relationship between structural manipulation and their photophysical properties provided guidance for further modification of cercosporin, which could be applied to more meaningful and challenging energy-transfer reactions.
- Zhang, Yan,Xia, Mingze,Li, Min,Ping, Qian,Yuan, Zhenbo,Liu, Xuanzhong,Yin, Huimin,Huang, Shuping,Rao, Yijian
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p. 15284 - 15297
(2021/11/01)
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- Semi-heterogeneous Dual Nickel/Photocatalysis using Carbon Nitrides: Esterification of Carboxylic Acids with Aryl Halides
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Cross-coupling reactions mediated by dual nickel/photocatalysis are synthetically attractive but rely mainly on expensive, non-recyclable noble-metal complexes as photocatalysts. Heterogeneous semiconductors, which are commonly used for artificial photosynthesis and wastewater treatment, are a sustainable alternative. Graphitic carbon nitrides, a class of metal-free polymers that can be easily prepared from bulk chemicals, are heterogeneous semiconductors with high potential for photocatalytic organic transformations. Here, we demonstrate that graphitic carbon nitrides in combination with nickel catalysis can induce selective C?O cross-couplings of carboxylic acids with aryl halides, yielding the respective aryl esters in excellent yield and selectivity. The heterogeneous organic photocatalyst exhibits a broad substrate scope, is able to harvest green light, and can be recycled multiple times. In situ FTIR was used to track the reaction progress to study this transformation at different irradiation wavelengths and reaction scales.
- Pieber, Bartholom?us,Malik, Jamal A.,Cavedon, Cristian,Gisbertz, Sebastian,Savateev, Aleksandr,Cruz, Daniel,Heil, Tobias,Zhang, Guigang,Seeberger, Peter H.
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supporting information
p. 9575 - 9580
(2019/06/25)
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- Oxalic acid as the: In situ carbon monoxide generator in palladium-catalyzed hydroxycarbonylation of arylhalides
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An efficient palladium-catalyzed hydroxycarbonylation reaction of arylhalides using oxalic acid as a CO source has been developed. The reaction features high safety, low catalyst loading, and a broad substrate scope, and provides a safe and tractable approach to access a variety of aromatic carboxylic acid compounds. Mechanistic studies revealed the decomposition pattern of oxalic acid.
- Shao, Changdong,Lu, Ailan,Wang, Xiaoling,Zhou, Bo,Guan, Xiaohong,Zhang, Yanghui
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supporting information
p. 5033 - 5040
(2017/07/10)
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- Synthesis of (3-(2-aminopyrimidin-4-yl)-4-hydroxyphenyl)phenyl methanone analogues as inhibitors of vascular endothelial growth factor receptor-2 kinase
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Angiogenesis is critical for tumor growth and mediated mainly by vascular endothelial growth factor (VEGF) signaling. Inhibition of the VEGF signaling pathway has emerged as one of the promising approaches for cancer therapy. VEGF receptor 2 (VEGFR-2) is
- More, Kunal N.,Lee, Jinho
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- Imidazole-containing condensed tricyclic compound and application thereof
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The invention discloses an imidazole-containing condensed tricyclic compound adopting the structure as shown in the formula (I) or pharmaceutically acceptable salts, stereisomers or prodrug molecules thereof. The imidazole-containing condensed tricyclic compound has the IDO1 activity regulation function, can enhance T-cell activation through blocking immune checkpoints IDO1, is used for treating IDO1-mediated immunosuppression, and therefore, can become an effective medicine for treating malignant tumors. When used together with checkpoint protein anti-body drugs or other anti-cancer drugs, the imidazole-containing condensed tricyclic compound can enhance the anti-cancer effect. Meanwhile, the imidazole-containing condensed tricyclic compound has the potential of effectively treating IDO1 abnormity related immunosuppressive diseases and has a high application value.
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Paragraph 0268
(2018/03/01)
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- Silica-supported boric acid catalyzed synthesis of dihydropyrimidin-2-ones, bis(indolyl)methanes, esters and amides
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Silica-supported boric acid (H3BO3-SiO2) has been established as a green, efficient and recyclable catalyst for the synthesis of dihydropyrimidin-2-ones, bis(indolyl)methanes, and acetylation of alcohols, phenols, amines and thiols under solvent free conditions. The main features of the present method include clean reaction, mild conditions, low loading of environment friendly catalyst and easy workup procedure. The catalyst can be recycled at least five times without any significant loss in activity.
- Kumar, Vishal,Singh, Chitra,Sharma, Upendra,Verma, Praveen K.,Singh, Bikram,Kumar, Neeraj
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- Palladium-catalyzed acetoxylation of arenes by novel sulfinyl n-heterocyclic carbene ligand complexes
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A series of novel ligands based on N-heterocyclic carbene and sulfoxide functionalities have been prepared and characterized. Pd(II) complexes have been synthesized by transmetalation from the corresponding NHC-Ag derivatives, and their behavior as catalysts has been studied in arene C-H bond oxidative activation. Studies conducted toward the elucidation of the reaction mechanism of the acetoxylation suggest a C-H activation step at Pd(IV) rather than Pd(II) intermediates.
- Tato, Francisco,Garcia-Dominguez, Andres,Cardenas, Diego J.
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supporting information
p. 7487 - 7494
(2014/04/03)
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- Synthesis, molecular modeling and preliminary biological evaluation of a set of 3-acetyl-2,5-disubstituted-2,3-dihydro-1,3,4-oxadiazole as potential antibacterial, anti-Trypanosoma cruzi and antifungal agents
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A series of 3-acetyl-2,5-disubstituted-2,3-dihydro-1,3,4-oxadiazole derivatives was synthesized and their activity screened in vitro against Staphylococcus aureus, Trypanosoma cruzi, and Candida albicans. The bioactivity was expressed as minimum inhibitory concentration (MIC) for S. aureus strains, and as fifty-percent inhibitory concentration (IC50) of parasite population growth for T. cruzi. A molecular modeling approach was performed to establish qualitative relationships regarding the biological data and the compounds' physicochemical properties. The 5-(4-OC4H9Ph, 5μ), and 5-(4-CO2CH3Ph, 5o) derivatives were the most active compounds for S. aureus ATCC 25923 (MIC = 1.95 -1.25 μg/mL) and T. cruzi (IC50 = 7.91 μM), respectively. Also, a preliminary evaluation against C. albicans involving some compounds was performed and the 5-(4-CH 3Ph, 5e) derivative was the most active compound (MIC = 3.28-2.95 μg/mL). In this preliminary study, all synthesized 3-acetyl-2,5- disubstituted-2,3-dihydro-1,3,4-oxadiazole derivatives were active against all microorganisms tested.
- Ishii, Marina,Jorge, Salom?o Dória,De Oliveira, Alex Alfredo,Palace-Berl, Fanny,Sonehara, Ieda Yuriko,Pasqualoto, Kerly Fernanda Mesquita,Tavares, Leoberto Costa
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experimental part
p. 6292 - 6301
(2011/12/02)
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- Simultaneous in-cell derivatization pressurized liquid extraction for the determination of multiclass preservatives in leave-on cosmetics
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An effective one-step sample preparation methodology for the determination of multiclass preservatives in cosmetics has been developed, applying, for the first time to this kind of matrix, pressurized liquid extraction (PLE) and a very simple, cheap, and fast derivatization procedure: acetylation with acetic anhydride and pyridine. A multifactorial experimental design has been used to evaluate and optimize the main experimental parameters potentially affecting the extraction process. In the final conditions the sample was mixed with Florisil as the dispersing sorbent and extracted with ethyl acetate for 15 min at 120 °C. One of the main goals of this work was to demonstrate the possibility of carrying out direct cosmetic preservative acetylation by simply adding the derivatization reagents into the PLE cell. The extract was then analyzed by GC/MS without any further cleanup or concentration step. The accuracy, precision, linearity, and detection limits (LODs) were evaluated to assess the performance of the proposed method. Quantitative recoveries were obtained, and relative standard deviation values were lower than 10% in all cases. The obtained LODs ranged from 0.000004% to 0.0001% (w/w), values far below the established restrictions in the European Cosmetics Regulation, making this multicomponent analytical method suitable for routine control. Finally, several cosmetic products such as moisturizing and antiwrinkle creams and lotions, hand creams, sunscreen and after-sun creams, baby lotions, and hair care products were analyzed. All the samples contained several of the target cosmetic ingredients, in some cases at quite high concentrations, although the actual European Cosmetics Regulation was fulfilled in all cases.
- Sanchez-Prado, Lucia,Lamas, J. Pablo,Lores, Marta,Garcia-Jares, Carmen,Llompart, Maria
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experimental part
p. 9384 - 9392
(2011/09/20)
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- The first general and selective palladium(II)-catalyzed alkoxycarbonylation of arylboronates: Interplay among benzoquinone-ligated palladium(0) complex, organoboron, and alcohol solvent
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Methoxycarbonylation of aryl- and alken-ylboron compounds was performed using the palladium (II) acetate/triphenylphosphine [PdACHTUNGTRENNUNG(OAc) 2/PPh3] catalyst with p-benzoquinone as a stoichiometric oxidant in methanol at ambient temperature to obtain the corresponding methyl esters in good yields. A wide variety of functional groups including various carbonyl functionalities, nitrile, nitro, sulfone, and unprotected pyrrole rings were tolerated in the methoxycarbonlation, while the use of higher alcohols except for tert-butanol afforded various pchlorobenzoates in moderate to high yields. The catalytic alkoxycarbonylation proceeded without any acid or base additive, and an oxidative transmetalation step is proposed to explain the exceptional efficacy of this protocol. DFT and MP2 calculations support the proposed mechanism.
- Yamamoto, Yoshihiko
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supporting information; experimental part
p. 478 - 492
(2010/07/03)
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- Selective oxidation of acetophenones bearing various functional groups to benzoic acid derivatives with molecular oxygen
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Acetophenones substituted by alkyl, alkoxy, acetoxy, and halogen groups were selectively oxidized with molecular oxygen to the corresponding benzoic acids by using the N,N',N"-trihydroxyisocyanuric acid (THICA)/cobalt(II) acetate [Co(OAc)2] and THICA/Co(OAc)2/manganese(II) acetate.
- Nakamura, Ryota,Obora, Yasushi,Ishii, Yasutaka
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experimental part
p. 1677 - 1684
(2011/02/25)
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- Counterattack mode differential acetylative deprotection of phenylmethyl ethers: Applications to solid phase organic reactions
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A counterattack protocol for differential acetylative cleavage of phenylmethyl ether has been developed. The phenylmethyl moiety is liberated as benzyl bromide that is isolated and reused providing advantages in terms of waste minimization/utilization and atom economy. The applicability of this methodology has been extended for solid phase organic reactions with the feasibility of reuse of the solid support.
- Chakraborti, Asit K.,Chankeshwara, Sunay V.
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experimental part
p. 1367 - 1370
(2009/07/04)
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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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- Al(OTf)3 as a highly efficient catalyst for the rapid acetylation of alcohols, phenols and thiophenols under solvent-free conditions
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Aluminium triflate (0.01-0.1 mol %) was found to be an efficient catalyst for the acylation of alcohols, phenols, thiols and sugars with acetic anhydride in high yields under solvent-free conditions in a short reaction time at room temperature. Racemization of optically active alcohols and epimerization of sugars were not observed. The acylation efficacy of various acyl donors was also investigated.
- Kamal, Ahmed,Khan, M. Naseer A.,Reddy, K. Srinivasa,Srikanth,Krishnaji
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p. 3813 - 3818
(2008/02/06)
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- An efficient and mild direct oxidative methyl esterification of aromatic aldehydes using NaBr and diacetoxyiodobenzene
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Diacetoxyiodobenzene combined with NaBr was found to be an efficient, mild and practical reagent for the oxidative methyl esterification of aldehydes.
- Karade,Shirodkar,Dhoot,Waghmare
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p. 274 - 276
(2007/10/03)
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- Zirconiuni(IV) chloride as a new, highly efficient, and reusable catalyst for acetylation of phenols, thiols, amines, and alcohols under solvent-free conditions
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Zirconium(IV) chloride has been found to be a new, highly efficient, and reusable catalyst for acetylation of structurally diverse phenols, thiols, amines, and alcohols under solvent-free condtions. Acetylation of sterically hindered and electron deficient phenols is achieved in excellent yields with stoichiometric amounts of Ac2O at room temperature. Acid-sensitive alcohols undergo acetylation with excellent chemoselectivity without competitive side reactions such as dehydration or rearrangement. The mild Lewis acid property of the catalyst enables the acetylation to be carried out with optically active substrates without any detrimental effect on the optical purity.
- Chakraborti, Asit K.,Gulhane, Rajesh
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p. 627 - 630
(2007/10/03)
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- Copper(II) Tetrafluoroborate-Catalyzed Acetylation of Phenols, Thiols, Alcohols, and Amines
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Copper(II) tetrafluoroborate efficiently catalyzes acetylation of structurally diverse phenols, alcohols, thiols, and amines with stoichiometric amounts of Ac2O under solvent-free conditions at room temperature. Acid-sensitive alcohols are smoothly acetylated without competitive side reactions. The reaction is influenced by the steric and electronic factors associated with the substrate as well as the anhydride. Acetylation of a sterically hindered substrate requires excess of anhydride and longer time. Acylation with less electrophilic anhydrides affords poor to moderate yields.
- Chakraborti, Asit K.,Gulhane, Rajesh,Shivani
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p. 111 - 115
(2007/10/03)
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- NOVEL 3-(2-AMINO-4-PYRIMIDINYL)-4-HYDROXYPHENYL KETONE DERIVATIVES
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The present invention relates to novel compounds having 3-(2-amino-4-pyrimidinyl)-4-hydroxyphenyl ketone structure, as being illustrated in Formula 1, for inhibition of angiogenesis receptor tyrosine kinases, in particular, VEGF receptor 2 kinase ("KDR")
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Page 22, 35, 36
(2010/02/08)
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- Perchloric acid adsorbed on silica gel as a new, highly efficient, and versatile catalyst for acetylation of phenols, thiols, alcohols, and amines
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Perchloric acid adsorbed on silica gel efficiently catalyses acetylation of structurally diverse phenols, alcohols, thiols, and amines under solvent free conditions.
- Chakraborti, Asit K.,Gulhane, Rajesh
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p. 1896 - 1897
(2007/10/03)
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- Fluoroboric acid adsorbed on silica gel as a new and efficient catalyst for acylation of phenols, thiols, alcohols, and amines
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Fluoroboric acid supported on silica gel efficiently catalyzes acylation of structurally diverse phenols, alcohols, thiols, and amines under solvent free conditions. Acid-sensitive alcohols are smoothly acylated without competitive side reactions.
- Chakraborti, Asit K.,Gulhane, Rajesh
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p. 3521 - 3525
(2007/10/03)
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- Indium(III) chloride as a new, highly efficient, and versatile catalyst for acylation of phenols, thiols, alcohols, and amines
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Indium(III) chloride efficiently catalyses the acylation of structurally diverse phenols, alcohols, thiols, and amines under solvent free conditions. Acid sensitive alcohols are smoothly acylated without competitive side reactions. Acylation of 2-hydroxynaphthalene is carried out with carboxylic acids adopting the mixed anhydride protocol using trifluoroacetic anhydride.
- Chakraborti, Asit K.,Gulhane, Rajesh
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p. 6749 - 6753
(2007/10/03)
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- Electrostatic catalysis by ionic aggregates: Scope and limitations of Mg(ClO4)2 as acylation catalyst
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Alkali and alkaline earth metal perchlorates exhibit electrostatic catalysis in the activation of anhydrides for the acylation reaction. Perchlorates with higher values of the charge-size function of the metal ion exhibit better catalytic activity following the order Mg(ClO4) 2>Ba(ClO4)2>LiClO4. Acylation of structurally diverse phenols, thiols, alcohols, and amines have been carried out with stoichiometric amounts of anhydride at room temperature under solvent free conditions in the presence of catalytic amount of Mg(ClO4) 2. Sterically hindered and electron deficient phenols are efficiently acylated. Acylation with sterically hindered anhydrides such as iso-butyric, pivalic, and benzoic anhydrides are carried out with phenols and alcohols in excellent yields. Acid-sensitive alcohols are acylated in excellent yields without any competitive side reactions.
- Chakraborti, Asit K.,Sharma, Lalima,Gulhane, Rajesh,Shivani
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p. 7661 - 7668
(2007/10/03)
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- Bismuth Oxide Perchlorate as a Highly Efficient Catalyst for Heteroatom Acylation under Solvent-Free Conditions
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Bismuth oxide perchlorate efficiently catalyzes the acetylation of structurally diverse phenols, alcohols, thiols, and amines under solvent free conditions. Sterically hindered and electron deficient phenols are acetylated in excellent yields with stoichiometric amounts of Ac2O at room temperature. Acylation of acid-sensitive alcohols is carried out efficiently without competitive side reactions. Optically active substrates are acetylated without any detrimental effect on the optical purity.
- Chakraborti, Asit K.,Gulhane, Rajesh,Shivani
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p. 1805 - 1808
(2007/10/03)
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- Lewis acid-catalyzed cleavage of carbamate and carbonate resins
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A procedure for the preparation of amides and esters on a Merrifield resin-bound benzyloxycarbonyl equivalent has been developed. Polymer-supported carbamates react cleanly with zinc bromide and the appropriate acyl halide in the presence of triethylamine to provide their corresponding amides in high yields and purities. Cleavage of resin-bound carbonates was carried out using the similar reagent systems in the absence of triethylamine to give acetates or benzoates. (C) 2000 Elsevier Science Ltd.
- Li,Lin,Yo
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p. 6619 - 6622
(2007/10/03)
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- Efficient one-pot formation of amides from benzyl carbamates: Application to solid-phase synthesis
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A convenient one-pot protocol for the conversion of benzyl carbamates to amides is described. The general applicability of the procedure is illustrated using various types of substrates. This new method proceeds rapidly under mild conditions, in good yields, and without noticeable racemization. This protocol was applied to solid-phase synthesis to prepare amides and esters from Merrifield resin-bound carbamates and carbonates. (C) 2000 Elsevier Science Ltd.
- Li, Wen-Ren,Yo, Ying-Chih,Lin, Yu-Sheng
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p. 8867 - 8875
(2007/10/03)
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- Novel chemoselective de-esterification of esters of polyacetoxy aromatic acids by lipases
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Candida cylindracea lipase (CCL) and porcine pancreatic lipase (PPL) have been used for deacetylation of peracetates of methyl and ethyl esters of six different polyphenolic acids in organic solvents. Exclusive de-esterification of the ester groups derived from the phenolic hydroxy and aliphatic acid over the ester group of the aromatic acid and aliphatic alcohol has been achieved affording the corresponding esters of phenolic acids in as high yields as 90-97%. The results have been corroborated with the mechanism of lipase action.
- Parmar, Virinder S.,Kumar, Ajay,Bicht, Kirpal S.,Mukherjee, Shubhasish,Prasad, Ashok K.,Sharma, Sunil K.,Wengel, Jesper,Olsen, Carl E.
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p. 2163 - 2176
(2007/10/03)
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- THERMAL CONVERSION OF METHYL 8-VINYL-3-OXO-2-OXABICYCLOOCT-5-EN-6-CARBOXYLATES TO TETRAHYDROCOUMARINS AND METHYL BENZOATES
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Methyl 8-methyl- and 8-methoxy-8-vinyl-3-oxo-2-oxabicyclooct-5-en-6-carboxylates (3 and 5), prepared by the Diels-Alder reaction of methyl 2-oxo-2H-pyran-5-carboxylate with 2-methyl- and 2-methoxy-1,3-butadienes, were converted into methyl 9-methyl- and 9-methoxy-3-oxo-2-oxabicyclodeca-4,8-diene-6-carboxylates (tetrahydrocoumarins) by a Cope rearrangement at about 140 deg C, respectively.On the other hand, 3 and 5 were transformed into methyl 4-isopropyl- and 4-acetylbenzoates via the reaction of methyl tricyclo2,7>oct-3-en-4-carboxylates at about 257 deg C in the presence of Pd-C, respectively.
- Matsui, Takanao,Matsushita, Yoh-ichi,Nakayama, Mitsuru
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p. 723 - 728
(2007/10/02)
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- Correlation of Carbon-13 Substituent-Induced Chemical Shifts: meta- and para-Substituted Methyl Benzoates
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Carbon-13 NMR spectra are reported for 69 substituted methyl benzoates in deuteriochloroform or in its mixture with dimethyl sulphoxide-d6.The substituent-induced chemical shifts (SCS) of the CO carbon correlate poorly with dual substituent parameters (DSP) in all possible modifications, and for meta derivatives in particular this correlation is both overparameterized and imprecise.A much better correlation was obtained with parameters (designated Bm, Bp and Cp) derived previously by principal component analysis (PCA) from a larger set.The SCS of the CH3 carbon correlate very well with the original simple Hammett equation, and no DSP treatment is needed.The clustering of substituents is not consequential in such a large set.KEY WORDS Methyl benzoates 13C NMR Substituent effects
- Budesinsky, Milos,Exner, Otto
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p. 585 - 591
(2007/10/02)
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