- Remarkable differences in photo and thermal (acid-catalyzed) reactivities between ortho-and para-acylcyclohexadienones as essential factors determining the overall efficiency of the photo-fries rearrangement
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Successful isolation of ortho and para - acylcyclohexadienones allowed us to comparatively study their ground- and excited-state behavior under a variety of conditions. In neutral solutions, the two isomeric cyclohexdienones showed completely different reactivities for photochemical and thermal reactions, while in acidic methanol both quantitatively afforded the corresponding transesterification product and naphthol. These studies help us understand the detailed photo-Fries rearrangement mechanism, which involves several crucial photochemical and thermal steps.
- Mori, Tadashi,Takamoto, Makoto,Saito, Hideaki,Furo, Takahiro,Wada, Takehiko,Inoue, Yoshihisa
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Read Online
- Photoredox-catalyzed reduction of halogenated arenes in water by amphiphilic polymeric nanoparticles
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The use of organic photoredox catalysts provides new ways to perform metal-free reactions controlled by light. While these reactions are usually performed in organic media, the application of these catalysts at ambient temperatures in aqueous media is of considerable interest. We here compare the activity of two established organic photoredox catalysts, one based on 10-phenylphenothiazine (PTH) and one based on an acridinium dye (ACR), in the light-activated dehalogenation of aromatic halides in pure water. Both PTH and ACR were covalently attached to amphiphilic polymers that are designed to form polymeric nanoparticles with hydrodynamic diameter DH ranging between 5 and 11 nm in aqueous solution. Due to the hydrophobic side groups that furnish the interior of these nanoparticles after hydrophobic collapse, water-insoluble reagents can gather within the nanoparticles at high local catalyst and substrate concentrations. We evaluated six different amphiphilic polymeric nanoparticles to assess the effect of polymer length, catalyst loading and nature of the catalyst (PTH or ACR) in the dechlorination of a range of aromatic chlorides. In addition, we investigate the selectivity of both catalysts for reducing different types of aryl-halogen bonds present in one molecule, as well as the activity of the catalysts for C-C cross-coupling reactions. We find that all polymer-based catalysts show high activity for the reduction of electron-poor aromatic compounds. For electron-rich compounds, the ACR-based catalyst is more effective than PTH. In the selective dehalogenation reactions, the order of bond stability is C-Cl > C-Br > C-I irrespective of the catalyst applied. All in all, both water-compatible systems show good activity in water, with ACR-based catalysts being slightly more efficient for more resilient substrates.
- Eisenreich, Fabian,Kuster, Tom H. R.,Palmans, Anja R. A.,van Krimpen, David
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- PCl3-mediated transesterification and aminolysis of tert-butyl esters via acid chloride formation
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A PCl3-mediated conversion of tert-butyl esters into esters and amides in one-pot under air is developed. This novel protocol is highlighted by the synthesis of skeletons of bioactive molecules and gram-scale reactions. Mechanistic studies revealed that this transformation involves the formation of an acid chloride in situ, which is followed by reactions with alcohols or amines to afford the desired products.
- Wu, Xiaofang,Zhou, Lei,Li, Fangshao,Xiao, Jing
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p. 491 - 497
(2021/01/20)
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- Oxidative esterification of alcohols by a single-side organically decorated Anderson-type chrome-based catalyst
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The direct esterification of alcohols with non-noble metal-based catalytic systems faces great challenges. Here, we report a new chrome-based catalyst stabilized by a single pentaerythritol decorated Anderson-type polyoxometalate, [N(C4H9)4]3[CrMo6O18(OH)3C{(OCH2)3CH2OH}], which can realize the efficient transformation from alcohols to esters by H2O2oxidation in good yields and high selectivity without extra organic ligands. A variety of alcohols with different functionalities including some natural products and pharmaceutical intermediates are tolerated in this system. The chrome-based catalyst can be recycled several times and still keep the original configuration and catalytic activity. We also propose a reasonable catalytic mechanism and prove the potential for industrial applications.
- Wang, Jingjing,Jiang, Feng,Tao, Chaofu,Yu, Han,Ruhlmann, Laurent,Wei, Yongge
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supporting information
p. 2652 - 2657
(2021/04/21)
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- Robust synthesis of NIR-emissive P-rhodamine fluorophores
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P-Rhodamines were accessed by implementing a robust three step sequence consisting of (i) addition of m-metallated anilines to dichlorophosphine oxides, (ii) selective dibromination, and (iii) cyclization of the diaryllithium reagents derived from the dib
- Arndt, Hans-Dieter,Nasufovic, Veselin,Sauer, Maria,Vilotijevic, Ivan
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supporting information
p. 1567 - 1571
(2020/03/06)
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- Methoxylation of Acyl Fluorides with Tris(2,4,6-trimethoxyphenyl)phosphine via C-OMe Bond Cleavage under Metal-Free Conditions
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Acyl fluorides are subjected to methoxylation with tris(2,4,6-trimethoxyphenyl)phosphine (TMPP) to afford the corresponding methyl esters in good to excellent yields. This transformation is featured by C(sp2)-OMe bond cleavage under metal-free conditions. Unprecedented utilization of TMPP as a methoxylating agent realized the installation of an OMe group into the desired products.
- Ishida, Takumi,Nishihara, Yasushi,Wang, Xiu,Wang, Zhenhua
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p. 7526 - 7533
(2020/06/27)
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- Synthesis and Characterization of Acridinium Dyes for Photoredox Catalysis
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Photoredox catalysis is a rapidly evolving platform for synthetic methods development. The prominent use of acridinium salts as a sustainable option for photoredox catalysts has driven the development of more robust and synthetically useful versions based on this scaffold. However, more complicated syntheses, increased cost, and limited commercial availability have hindered the adoption of these catalysts by the greater synthetic community. By utilizing the direct conversion of a xanthylium salt into the corresponding acridinium as the key transformation, we present an efficient and scalable preparation of the most synthetically useful acridinium reported to date. This divergent strategy also enabled the preparation of a suite of novel acridinium dyes, allowing for a systematic investigation of substitution effects on their photophysical properties.
- White, Alexander R.,Wang, Leifeng,Nicewicz, David A.
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supporting information
p. 827 - 832
(2019/04/25)
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- Aldehydes as potential acylating reagents for oxidative esterification by inorganic ligand-supported iron catalysis
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The oxidative esterification of various aldehydes with alcohols could be achieved by a heterogeneous iron(iii) catalyst supported on a ring-like POM inorganic ligand under mild conditions, affording the corresponding esters, including several drug molecules and natural products, in high yields. ESI-MS and control experiments demonstrated that POM-FeV(O) was the active catalytic species and the plausible mechanism was presented. More importantly, the 6th run of the iron catalyst recycles shows only a slight decrease in the yield.
- Yu, Han,Wang, Jingjing,Wu, Zhikang,Zhao, Qixin,Dan, Demin,Han, Sheng,Tang, Jiangjiang,Wei, Yongge
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supporting information
p. 4550 - 4554
(2019/08/21)
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- Palladium-Catalyzed Visible-Light-Driven Carboxylation of Aryl and Alkenyl Triflates by Using Photoredox Catalysts
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A visible-light-driven carboxylation of aryl and alkenyl triflates with CO2 is developed by using a combination of Pd and photoredox catalysts. This reaction proceeds under mild conditions and can be applied to a wide range of substrates including acyclic alkenyl triflates.
- Shimomaki, Katsuya,Nakajima, Tomoya,Caner, Joaquim,Toriumi, Naoyuki,Iwasawa, Nobuharu
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supporting information
p. 4486 - 4489
(2019/06/24)
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- Palladium-Catalyzed Intermolecular Arylcarbonylation of Unactivated Alkenes: Incorporation of Bulky Aryl Groups at Room Temperature
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A palladium-catalyzed intermolecular arylcarbonylation of unactivated alkenes has been developed. Unsymmetrical diaryliodonium salts (DAISs) were used as arylation reagents, the bulky aryl group (ArL) of which was exclusively incorporated into the arylcarbonylated products, which contained the ArL group and a carboxylic ester group at the α- and β-carbon position, respectively, of the original terminal C?C double bond. The reaction features excellent chemo- and regioselectivity, high functional-group tolerance, and very mild reaction conditions.
- Li, Xiang,Chen, Pinhong,Liu, Guosheng
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supporting information
p. 15871 - 15876
(2018/11/23)
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- Copper-Catalyzed O-Methylation of Carboxylic Acids Using DMSO as a Methyl Source
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A copper-catalyzed O-methylation of carboxylic acids using dimethyl sulfoxide (DMSO) as the methyl source is disclosed. This transformation exhibits a broad substrate scope and excellent functional group tolerance. Mechanistic studies indicate that a methyl radical is generated from dimethyl sulfoxide in the reaction process.
- Jia, Jing,Jiang, Qing,Zhao, An,Xu, Bin,Liu, Qiang,Luo, Wei-Ping,Guo, Can-Cheng
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p. 421 - 428
(2016/01/28)
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- Steric effect of substituents in haloarenes on the rate of cross-coupling reactions
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The relative reactivity of ortho- and para-methyl-substituted iodoarenes in the Sonogashira reaction and palladium-catalyzed methoxycarbonylation, as well as of similarly substituted bromoarenes in the Suzuki reactions and cobalt-catalyzed methoxycarbonylation, was studied. Introduction of a methyl group into the para position of aryl halide slows down the cross-coupling. o-Methylhaloarenes are less reactive in palladiumcatalyzed reactions as compared to both unsubstituted haloarene and para-substituted analog. The presence of a methyl group in the ortho position with respect to the reaction center accelerates cobalt-catalyzed methoxycarbonylation.
- Khaibulova, T. Sh.,Boyarskaya,Boyarskii
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p. 360 - 365
(2013/07/26)
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- Direct conversion of N -alkoxyamides to carboxylic esters through tandem nbs-mediated oxidative homocoupling and thermal denitrogenation
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Treatment of N-alkoxyamides with NBS in toluene was found to conveniently afford the corresponding carboxylic esters, including those bearing a bulky or long-chain substituent, in satisfactory to excellent yields. This approach not only represents a convenient and economic approach to a direct transformation of an alkoxyamide moiety into the carboxylic ester functional group, via oxidative homocoupling and the subsequent thermal denitrogenation, but also facilitates the synthesis of sterically hindered carboxylic esters.
- Zhang, Ningning,Yang, Rui,Zhang-Negrerie, Daisy,Du, Yunfei,Zhao, Kang
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p. 8705 - 8711
(2013/09/24)
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- Selective oxidation of alcohols to esters using heterogeneous Co 3O4-N@C catalysts under mild conditions
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Novel cobalt-based heterogeneous catalysts have been developed for the direct oxidative esterification of alcohols using molecular oxygen as benign oxidant. Pyrolysis of nitrogen-ligated cobalt(II) acetate supported on commercial carbon transforms typical homogeneous complexes to highly active and selective heterogeneous Co3O4-N@C materials. By applying these catalysts in the presence of oxygen, the cross and self-esterification of alcohols to esters proceeds in good to excellent yields.
- Jagadeesh, Rajenahally V.,Junge, Henrik,Pohl, Marga-Martina,Radnik, Joerg,Brueckner, Angelika,Beller, Matthias
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supporting information
p. 10776 - 10782
(2013/08/23)
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- A facile synthesis of (S)-felodipine
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A short and facile synthesis of (S)-felodipine was developed starting from (R)-glycidol as the source of the chiral auxiliary. 2-Hydroxyethyl esters were found to undergo selective transesterification reactions in the presence of other esters. This selective transesterification reaction was applied to the synthesis of (S)-felodipine through selective substitution of the 2-hydroxyethyl group possessing chiral ester with sodium methoxide.
- Kwon, Kuktae,Shin, Jung A.,Lee, Hee-Yoon
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scheme or table
p. 10222 - 10228
(2012/01/05)
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- Rhodium(III)-catalyzed heterocycle synthesis using an internal oxidant: Improved reactivity and mechanistic studies
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Directing groups that can act as internal oxidants have recently been shown to be beneficial in metal-catalyzed heterocycle syntheses that undergo C-H functionalization. Pursuant to the rhodium(III)-catalyzed redox-neutral isoquinolone synthesis that we recently reported, we present in this article the development of a more reactive internal oxidant/directing group that can promote the formation of a wide variety of isoquinolones at room temperature while employing low catalyst loadings (0.5 mol %). In contrast to previously reported oxidative rhodium(III)-catalyzed heterocycle syntheses, the new conditions allow for the first time the use of terminal alkynes. Also, it is shown that the use of alkenes, including ethylene, instead of alkynes leads to the room temperature formation of 3,4-dihydroisoquinolones. Mechanistic investigations of this new system point to a change in the turnover limiting step of the catalytic cycle relative to the previously reported conditions. Concerted metalation-deprotonation (CMD) is now proposed to be the turnover limiting step. In addition, DFT calculations conducted on this system agree with a stepwise C-N bond reductive elimination/N-O bond oxidative addition mechanism to afford the desired heterocycle. Concepts highlighted by the calculations were found to be consistent with experimental results.
- Guimond, Nicolas,Gorelsky, Serge I.,Fagnou, Keith
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supporting information; experimental part
p. 6449 - 6457
(2011/06/16)
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- Oxoammonium salt/NaClO2: An expedient, catalytic system for one-pot oxidation of primary alcohols to carboxylic acids with broad substrate applicability
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A facile, green, one-pot oxidation of primary alcohols to carboxylic acids with broad substrate applicability has been developed by employing an expedient catalytic system consisting of 1-Me-AZADO+X-/NaClO 2. The Royal Society of Chemistry.
- Shibuya, Masatoshi,Sato, Takahisa,Tomizawa, Masaki,Iwabuchi, Yoshiharu
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supporting information; experimental part
p. 1739 - 1741
(2009/08/08)
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- Computational and experimental structure-reactivity relationships: evidence for a side reaction in Alpine-Borane reductions of d-benzaldehydes
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Extraordinary stereoselectivity, approaching 100%, has been reported in the reductions of d-benzaldehydes by B-isopinocampheyl-9-borabicyclo[3.3.1]nonane (Alpine-Borane). This is likely because of the extreme size disparity of groups on either side of the carbonyl. Here, we present a structure-reactivity study whereby the reductions of variably substituted d-benzaldehydes are explored using highly sensitive measures for enantiomeric excess and relative reactivity. These results are compared to the relative rates predicted from density functional calculations. The results indicate that 2,6-disubstitution adversely affects the stereoselectivity by means of a non-selective reduction via the dehydroboration product of Alpine-Borane, 9-borabicyclo[3.3.1]nonane.
- Zhu, Hui,Soledad Reyes,Meyer, Matthew P.
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supporting information; experimental part
p. 6803 - 6806
(2010/04/29)
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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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- PROCESS FOR PRODUCING CARBOXYLIC ACID FROM PRIMARY ALCOHOL
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To provide an industrially-useful and environmentally-friendly novel oxidation reaction. A process for producing a carboxylic acid from a primary alcohol, which comprises using an alkali metal chlorite as a co-oxidizing agent and using, as a catalyst, an oxoammonium salt of the formula (1):
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Page/Page column 5-6
(2009/05/28)
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- Facile preparation of polymer-supported methyl sulfonate and its recyclable use for methylation of carboxylic acids and amines
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A simple and efficient one-pot procedure for the preparation of polymer-supported methyl sulfonate from the reaction of polymer-supported sulfonic acid with trimethyl orthoacetate was achieved, and it could be successfully used for efficient methylation of carboxylic acids, phosphonic acids, sulfinic acids, amines, thiol, and phenol. Moreover, the polymer reagent could be recovered, regenerated, and reused easily for the same reactions. Georg Thieme Verlag Stuttgart.
- Yoshino, Tomonori,Togo, Hideo
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p. 517 - 519
(2007/10/03)
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- 13C and 1H nuclear magnetic resonance of methyl-substituted acetophenones and methyl benzoates: Steric hindrance and inhibited conjugation
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The 1H and 13C NMR spectra of 14 methyl-substituted acetophenones and 14 methyl-substituted methyl benzoates were assigned and interpreted with respect to the conformation of the Car - C(O) bond. The substituent effects are proportional in the two series and can be divided into polar and steric: each has different effects on the 13C SCS of the individual atoms. In the case of C atoms C(O), C(1) and CH3(CO), the steric effects were quantitatively separated by comparing SCS in the ortho and para positions. The steric effects are proportional for the individual C atoms and also to steric effects estimated from other physical quantities. However, they do not depend simply on the angle of torsion φ of the functional group as anticipated hitherto. A better description distinguishes two classes of compounds: sterically not hindered or slightly hindered planar molecules and strongly sterically hindered, markedly non-planar. In order to confirm this reasoning without empirical correlations, the J(C,C) coupling constants were measured for three acetophenone derivatives labeled with 13C in the acetyl methyl group. The constants confirm unambiguously the conformation of 2-methylacetophenone; their zero values are in accord with the conformation of 2,6-dimethylacetophenone. The zero values in the unsubstituted acetophenone are at variance with previous erroneous report but all J(C,C) values are in accord with calculations at the B3LYP/6-311++G(2d,2p)// B3LYP/6-311+G(d,p) level. Copyright
- Budesinsky, Milos,Kulhanek, Jiri,Boehm, Stanislav,Cigler, Petr,Exner, Otto
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p. 844 - 851
(2007/10/03)
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- Development and applications of a practical continuous flow microwave cell
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A series of synthetic transformations were successfully and safely scaled up to multigram quantities using focused microwave irradiation with a continuous flow reaction cell that was developed in-house and which can be easily adapted to commercially avail
- Wilson, Noel S.,Sarko, Christopher R.,Roth, Gregory P.
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p. 535 - 538
(2013/09/05)
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- Reactivity of diacyloxyiodobenzenes toward trivalent phosphorus nucleophiles
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The reaction of diacyloxyiodobenzenes and tetravalent phosphorus nucleophiles was investigated. It was established that both H-phosphonates and secondary phosphine oxides react with diacetoxyiodobenzene in alcohols in the presence of sodium alcoholates yi
- Makowiec, Slawomir,Rachon, Janusz
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p. 352 - 359
(2007/10/03)
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- Microwave promoted facile synthesis of methyl and ethyl carboxylates
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Microwave irradiation of carboxylic acids with trialkyl orthoacetate in solvent-free conditions afforded an efficient method for alkylation of carboxylic acids to corresponding alkyl carboxylates.
- Lee, Jong Chan,Song, In-Goul,Park, Jin Young
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p. 2209 - 2213
(2007/10/03)
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- Regioselectivity of the Base-Induced Ring Cleavage of 1-Oxygenated Derivatives of Cyclobutabenzene
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Oxy anions 3 generated from 1,2-dihydrocyclobutabenzen-1-ones 1 through addition of a charged nucleophile or from 1-hydroxy-1,2-dihydrocyclobutabenzenes 2 by deprotonation with base lead to stable products through distal and/or proximal cleavage of the strained four-membered ring via benzyl carbanion 4 and/or aryl carbanion 5. A systematic study of this process reveals the relative stability of the two isomeric carbanions 4 and 5 as a key factor in determining the course of the ring-cleavage reaction. While benzyl carbanions 4 can be trapped with carbon electrophiles, attempts at trapping aryl carbanions 5 with electrophiles other than H+ failed. In protic solvents, the magnesium salt of the tertiary alcohol 2 shows an increased rate of proximal cleavage as compared to its alkali salts. From this, we conclude that, in contrast to benzyl carbanions 4, free aryl carbanions 5 are of transient existence only. Proximal C,C-bond cleavage seems to occur either through protonation of 5 from a fast, reversible equilibrium 3?5 in which 3 strongly predominates, or in protic solvents possibly even through a rate-limiting protonation of 3 at the aromatic C-atom, bypassing free anion 5 altogether. Thus, additional factors other than just the relative stability of isomeric carbanions 4 and 5 are of importance in determining the regiochemistry of the base-induced C,C-bond cleavage in ketones 1 and in alcohols 2.
- Gokhale, Abha,Schiess, Peter
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p. 251 - 267
(2007/10/03)
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- Sterically Hindered Carboxylic Acid Esters
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Methods have been developed for preparation of esters formed by sterically hindered benzoic acids and various alcohols, which were difficult to obtain previously. The methods are based on the reaction of carbenium ions, generated from primary aliphatic N-nitroamines by the action of nitrous acid or Lewis acids, with carboxylic acid at the sterically accessible oxygen atom of the carboxy group. Reactions of nitrobenzoic acids and benzenepolycarboxylic acids with 2,2,2-trinitroethyl hydrogen sulfate provide an effective method for preparation of corresponding trinitroethyl esters.
- Bagal,Ishchenko,Nikolaev
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p. 1731 - 1738
(2007/10/03)
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- Oxidation of Aromatic Compounds. II. Oxidation of Methyl Derivatives of Benzoic Acid and Acetophenone in the System HSO3F-PbO2
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Low-temperature oxidation of methyl derivatives of benzoic acid and acetophenone in the system HSO3F-PbO2 proceeds with intermediate formation of radical cations and results in replacement of hydrogen atom in methyl group or benzene ring.The reaction allows preparation of various substituted derivatives of benzyl alcohols and alkylated phthalides.
- Rudenko, A. P.,Korovina, N. S.
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p. 1084 - 1088
(2007/10/03)
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- Development and Application of a Continuous Microwave Reactor for Organic Synthesis
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A laboratory-scale continuous microwave reactor (CMR) has been developed and used to conduct organic syntheses routinely, rapidly, and safely in a range of solvents, under pressures up to 1400 kPa and at temperatures up to 200 deg C.Advantages and applications of the CMR are discussed, along with the rationale for the design.Reactions carried out with the CMR included nucleophilic substitution, addition, esterification, transesterification, acetalization, amidation, base- and acid-catalyzed hydrolysis, isomerization, decarboxylation, and elimination.Name reactions included the Michael addition, Hofmann degradation, Williamson ether synthesis, and the Mannich, Finkelstein, Baylis-Hillman, and Knoevenagel reactions.
- Cablewski, Teresa,Faux, Alan F.,Strauss, Christopher R.
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p. 3408 - 3412
(2007/10/02)
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- Concepts of sterically hindered resonance and buttressing effect: Gas-phase acidities of methyl-substituted benzoic acids and basicities of their methyl esters
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Two classical terms "Steric Hindrance to Resonance" and "Buttressing Effect" are revisited on the basis of the gas-phase acidities of nine methyl-substituted benzole acids and of the gas-phase basicities of their methyl esters, measured using FT- ICR spectrometry. By combining these data with published heats of formation of the neutrals and by using the principle of isodesmic reactions, relative enthalpies of formation were evaluated separately for the acid molecules, their anions (deprotonated), and their protonated cations (substituted by the protonated forms of the corresponding methyl esters). Energies of all species were also calculated at the semiempirical level (AMI). Substituent effects on the gas-phase acidity are similar to those on the acidity in water. All the methyl groups have a stabilizing polar effect, and o-methyl groups have a destabilizing steric effect, both effects increasing from the deprotonated forms to the acid molecules and then to the protonated forms. Separation of the two effects was attempted, assuming equal polar effects in the ortho and para positions. The results are internally consistent: their detailed analysis is in favor of a primary steric effect rather than a steric inhibition of resonance. The latter must be relatively weaker and operating only in 2,6-dimethyl derivatives, which are certainly nonplanar. In the literature this concept has been used too broadly, even for compounds for which the nonplanar conformation has not been proven. The concept of buttressing effect has been confirmed for methyl-substituted benzoic acids, but it is formulated more generally and more exactly. According to the new definition, it can be observed even for nonadjacent substituants.
- Decouzon, Michèle,Ertl, Peter,Exner, Otto,Gal, Jean-Fran?ois,Maria, Pierre-Charles
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p. 12071 - 12078
(2007/10/02)
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- Cyclisation reactions of 2-substituted biphenyl-2'-yldiazonium salts leading to O-alkyldibenzofuranium and S-alkyldibenzothiophenium salts: Modified Meerwein reagents
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The preparation of 2-amino-2'-methoxybiphenyl and 2-amino-2'-thiomethoxybiphenyl and analogues and their transformation into diazonium salts and hence into dibenzofuranium and dibenzothiophenium salts is described together with their use as alkylating agents.
- Downie,Heaney,Kemp,King,Wosley
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p. 4005 - 4016
(2007/10/02)
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- YLURES SANS SEL, EVOLUTION EN PHOSPHORANES ET EQUILIBRE YLURE - PHOSPHORANE; INFLUENCE DES REACTIFS DE PIEGEAGE: III PIEGEAGE PROTIQUE
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This work is a contribution to rationalize the trapping behaviour of the 1,3 dipolar species created by addition of methoxy tetramethyl-dioxaphospholane-1,3,2 on dimethylacetylene dicarboxylate.In the past, we have given examples with protic reagents (met
- Jaafar, B. Ben,Manouni, D. El.,Burgada, R.,Leroux, Y.
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- CLEAVAGE OF THE PHENACYL ESTERS OF CARBOXYLIC AND THIOCARBOXYLIC ACIDS BY METAL ALKOXIDES
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During the cleavage of phenacyl esters with general formula XC6H4COCH2OCOR by metal alkoxides in alcohols and in ether-alcohol solutions the acids, esters, and ethers are formed as a result of cleavage of the C-C bond.The solvent participates in the formation of the ether and gives rise to transesterification of RCOOCH3 with catalytic participation of the metal alkoxide.The reactivity of the phenacyl esters of the thio acids is much higher.Before dissociation the esters of substituted benzoins C6H5COCH(OCOCH3).C6H4X-4 undergo irreversible rearrangement with the formation of isomeric products.
- Morozov, A. A.
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p. 1138 - 1143
(2007/10/02)
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- Carbonylation of Organomercury Compounds: A General Synthesis of Carboxylic Acids and Esters
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Organomercury compounds react with carbon monoxide in aqueous or alcoholic media to give good yields of carboxylic acids or esters.The carboxyl group is introduced selectively at the site of the carbon-mercury bond.Homogeneous group 9 and 10 metal complexes catalyze this carbonylation reaction, which yields mercury(0) as the inorganic byproduct.The mercuration-carbonylation sequence represents a general synthesis of carboxylic acids and esters.
- Baird, William C.,Hartgerink, Ronald L.,Surridge, John H.
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p. 4601 - 4605
(2007/10/02)
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- THERMAL ADDITION REACTIONS TO BENZOCYCLOBUTENONES STUDIED BY FLASH PHOTOLYSIS
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Ortho-quinoid vinylketenes 2 have been generated thruogh flash photolysis of benzocyclobutenones 1.A kinetic study of intermolecular addition reactions of 2 competing with the recyclization 2 -> 1 reveals strikingly different substituent effects for the addition of methanol and of dienophiles.
- Schiess, P.,Eberle, M.,Huys-Francotte, M.,Wirz, J.
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p. 2201 - 2204
(2007/10/02)
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- Copper Ion Promoted Esterification of S-2-Pyridyl Thioates and 2-Pyridyl Esters. Efficient Methods for the Preparation of Hindered Esters
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The esterification of the S-2-pyridyl thioates and 2-pyridyl esters with alcohols in acetonitrile is greatly facilitated by the addition of cupric bromide and copper ion is observed to catalyze the reaction.The ester formation is found to be sensitive to solvents, metal salts, and reaction temperatures.The esterification of S-2-pyridyl thioates is much more rapid than the esterification of 2-pyridyl esters under the reaction conditions employed.This method is exceedingly effective in the preparation of sterically hindered esters and has advantages over known methods in many respects such as high yields, the mildness of the reaction, and the rapidity of the reaction.
- Kim, Sunggak,Lee, Jae In
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p. 1712 - 1716
(2007/10/02)
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- Studies on Electrolytic Substitution Reactions. XVII. Selective Nuclear Acetoxylation of Alkylaromatic Compounds
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Anodic nuclear monoacetoxylation of alkylaromatics (p-xylene, isodurene, mesitylene, durene) can be achieved with high selectivity with respect to the side-chain acetate by carrying out the electrolysis in the presence of Pd on carbon in a nondevided cell.This arrangement utilizes cathodically generated hydrogen to effect cleavage of the benzylic acetate as it is formed, thus continuously regenerating the substrate.The nuclear acetate which is resistant toward hydrogenolysis accumulates in the reaction moxture.
- Eberson, Lennart,Oberrauch, Ermanno
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p. 193 - 196
(2007/10/02)
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- NEW METHODS AND REAGENTS IN ORGANIC SYNTHESIS. 14. A SIMPLE EFFICIENT PREPARATION OF METHYL ESTERS WITH TRIMETHYLSILYLDIAZOMETHANE (TMSCHN2) AND ITS APPLICATION TO GAS CHROMATOGRAPHIC ANALYSIS OF FATTY ACIDS
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Trimethylsilyldiazomethane (TMSCHN2), known as a stable and safe substitute for highly toxic and explosive diazomethane in the Arndt-Eistert synthesis and homologation of carbonyl compounds, has smoothly reacted with various carboxylic acids in methanolic benzene solution to give the corresponding methyl esters in excellent yields.Keyords: trimethylsilyldiazomethane; carboxylic acid; methyl ester; esterification; fatty acid; gas chromatographic analysis
- Mashimoto, Norio,Aoyama, Toyohiko,Shioiri, Takayuki
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p. 1475 - 1478
(2007/10/02)
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- Process for electrolytic synthesis of polyalkylbiphenylpolycarboxylic acid compounds
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Process for coupling alkyl esters of polyalkylbenzoic acid to prepare polyalkylbiphenylpolycarboxylic acid compounds which comprises anodically oxidizing said alkyl esters in a non-nucleophilic media by applying a source of direct current in liquid phase at atmospheric pressure and temperatures from -30° to 80° C. The biphenyl acid compounds are useful in the formation of polyester resins, including alkyds, and fiber-forming polymers.
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