- Rhodium(III)-Catalyzed Aldehyde C?H Activation and Functionalization with Dioxazolones: An Entry to Imide Synthesis
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A rhodium(III)-based catalytic system has been used to develop a C?H bond activation of benzaldehyde derivatives and subsequent functionalization with dioxazolones in order to afford imides. The importance of the nature of the directing group to perform selectively the aldehydic C?H bond activation has been highlighted. The scope investigation showed that this transformation could be applied to various dioxazolones and many benzaldehyde derivatives as well as an acrolein derivative. Derivatization reactions of the imide products demonstrated the synthetic utility of this rhodium-catalyzed aldehydic C?H amidation.
- Bellière-Baca, Virginie,Clavier, Hervé,Hérault, Damien,Massouh, Joe,Petrelli, Antoine
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supporting information
(2022/01/06)
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- Nickel-Catalyzed Inter- and Intramolecular Aryl Thioether Metathesis by Reversible Arylation
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A nickel-catalyzed aryl thioether metathesis has been developed to access high-value thioethers. 1,2-Bis(dicyclohexylphosphino)ethane (dcype) is essential to promote this highly functional-group-tolerant reaction. Furthermore, synthetically challenging macrocycles could be obtained in good yield in an unusual example of ring-closing metathesis that does not involve alkene bonds. In-depth organometallic studies support a reversible Ni0/NiII pathway to product formation. Overall, this work not only provides a more sustainable alternative to previous catalytic systems based on Pd, but also presents new applications and mechanistic information that are highly relevant to the further development and application of unusual single-bond metathesis reactions.
- Delcaillau, Tristan,Bismuto, Alessandro,Lian, Zhong,Morandi, Bill
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supporting information
p. 2110 - 2114
(2019/12/24)
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- Unexpected formation of 4,7-dihalobenzo[b]thiophenes using Ohira-Bestmann reagent and reactivity of the halogen-substituted benzo[b]thiophenes in Suzuki-Miyaura coupling with phenylboronic acid
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Reaction of 2-(1-adamantylsulfanyl)-3,6-dihalobenzaldehydes with Ohira-Bestmann reagent gave 4,7-dihalobenzo[b]thiophenes along with normal alkyne products. Nine types of 4,7-dihalobenzo[b]thiophenes bearing chlorine, bromine, or iodine atoms, were prepared by this method. Regioselectivity in Suzuki-Miyaura cross coupling reactions of the 4,7-dihalobenzo[b]thiophenes with PhB(OH)2 was also studied.
- Toyota, Kozo,Mutoh, Hirotaka,Kishi, Hiroki,Mikami, Shinichi,Tanaka, Hiroki,Yoshida, Shuhei,Naganuma, Daisuke
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p. 1355 - 1374
(2019/12/23)
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- Construction of highly functionalized thiophene and benzo[b]thiophene derivatives via a sequence of propargyl–allenyl isomerization/cyclization/demethylation
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An efficient one-pot protocol for the synthesis of functionalized thiophene and benzo[b]thiophene derivatives was developed via a sequence of propargyl–allenyl isomerization/cyclization/demethylation. As a result of the readily accessible starting materials, simple operation, and mild conditions, this reaction should have potential utility in organic synthesis.
- Chen, Dianpeng,Xing, Gangdong,Chen, Xueyuan,Yao, Jinzhong,Zhou, Hongwei
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supporting information
p. 5124 - 5126
(2016/11/09)
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- A convenient method for the synthesis of aryl methyl sulfides via Cu(I)-mediated methylthiolation of haloarenes with DMSO
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An efficient process for the Cu(I)-mediated methylthiolation of haloarenes using simple and readily available DMSO as a convenient and environment friendly source of SMe moiety has been developed. In the presence of CuI and DABCO, a variety of aryl/heteroaryl halides reacted with DMSO to afford corresponding aryl methyl sulfides in good to excellent yields.
- Ghosh, Ketaki,Ranjit, Sadananda,Mal, Dipakranjan
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supporting information
p. 5199 - 5202
(2015/08/19)
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- The Key Role of the Nonchelating Conformation of the Benzylidene Ligand on the Formation and Initiation of Hoveyda-Grubbs Metathesis Catalysts
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Experimental studies of Hoveyda-Grubbs metathesis catalysts reveal important consequences of substitution at the 6-position of the chelating benzylidene ligand. The structural modification varies conformational preferences of the ligand that affects its exchange due to the interaction of the coordinating site with the ruthenium center. As a consequence, when typical S-chelated systems are formed as kinetic trans-Cl2 products, for 6-substituted benzylidenes the preference is altered toward direct formation of thermodynamic cis-Cl2 isomers. Activity data and reactions with tricyclohexylphosphine (PCy3) support also a similar scenario for O-chelated complexes, which display fast trans-Cl2?cis-Cl2 equilibrium observed by NMR EXSY studies. The presented conformational model reveals that catalysts, which cannot adopt the optimal nonchelating conformation of benzylidene ligand, initiate through a high-energy associative mechanism.
- Bieszczad, Bartosz,Barbasiewicz, Micha?
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supporting information
p. 10322 - 10325
(2015/07/07)
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- Aryl methyl sulfides via SNAr using DMSO as the source of the thiomethyl moiety
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A unique synthesis of aryl methyl sulfides is reported proceeding via reduction of dimethylsulfoxide to dimethylsulfide at elevated temperature in the presence of Hunig's base followed by nucleophilic aromatic substitution and demethylation. Activated aryl fluorides, chlorides, and nitrobenzenes are suitable substrates with 13 examples provided. Dimethylsulfoxide serves as a simple and inexpensive formal source of the thiomethyl moiety.
- Jones-Mensah, Ebenezer,Magolan, Jakob
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supporting information
p. 5323 - 5326
(2015/01/16)
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- SULFUR CHELATED RUTHENIUM COMPOUNDS USEFUL AS OLEFIN METATHESIS CATALYSTS
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Sulfur chelated ruthenium compounds represented by the following formula: wherein M indicates the ruthenium metal bound to a benzylidene carbon; R represents C1-C7 alkyl group or optionally substituted aryl; X1 and X2 each independently represent halogen; Y1 and Y2 each independently denote unsubstituted or alkyl-substituted phenyl; and Z independently represents hydrogen, electron withdrawing or electron donating substituent, with m being an integer from 1 to 4, and processes and compositions related thereto.
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Paragraph 0058
(2014/06/23)
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- Intermolecular alkyne hydroacylation. mechanistic insight from the isolation of the vinyl intermediate that precedes reductive elimination
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The isolation of the branched alkenyl intermediate that directly precedes reductive elimination of the final α,β-unsaturated ketone product is reported for the hydroacylation reaction between the alkyne HC≡CAr F (ArF = 3,5-(CF3)2C 6H3) and the β-S-substituted aldehyde 2-(methylthio)benzaldehyde: [Rh(fac-κ3-DPEphos)(C(=CH 2)ArF)(C(O)C6H4SMe) 2][CB11H12]. The structure of this intermediate shows that, in this system at least, hydride migration rather than acyl migration occurs. Kinetic studies on the subsequent reductive elimination to form the crystallographically characterized ketone-bound product [Rh(cis-κ2-DPEphos)(η2:η2, κ1-H2C=C(ArF)C(=O)(C6H 4SMe)][CB11H12] yield the following activation parameters for reductive elimination, which follows first-order kinetics (k obs = (6.14 ± 0.04) × 10-5 s-1, 324 K): ΔH = 95 ± 2 kJ mol-1, ΔS = -32 ± 7 J K-1 mol-1, ΔG(298 K) = 105 ± 4 kJ mol-1. Mechanistic studies, including selective deuteration experiments, show that hydride insertion is not reversible and also reveal that an interesting isomerization process is occurring between the two branched alkenyl protons that is suggested to occur via a metallocyclopropene intermediate. During catalysis, the consumption of substrates and evolution of products follow pseudo zero-order kinetics. The observation of both linear and branched products under stoichiometric and catalytic regimes, in combination with kinetic modeling, allows for an overall mechanistic scheme to be presented. Partitioning of linear and branched pathways at the hydride insertion step occurs with an approximate 2:1 selectivity, while reductive elimination of the linear product is at least 3 orders of magnitude faster than that from the branched. An explanation for the large difference in rate of reductive elimination in this system, as recently outlined by Goldman, Krogh-Jespersen, and Brookhart, is that steric crowding in branched intermediates can slow C-C reductive elimination even though such species are higher in energy than their linear analogues, if the rotation of the vinyl group to the appropriate orientation is inhibited by steric crowding in the branched isomers.
- Pawley, Rebekah J.,Huertos, Miguel A.,Lloyd-Jones, Guy C.,Weller, Andrew S.,Willis, Michael C.
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p. 5650 - 5659
(2012/11/14)
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- Studies on electronic effects in O-, N- and S-chelated ruthenium olefin-metathesis catalysts
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A short overview on the structural design of the Hoveyda-Grubbs-type ruthenium initiators chelated through oxygen, nitrogen or sulfur atoms is presented. Our aim was to compare and contrast O-, N- and S-chelated ruthenium complexes to better understand the impact of electron-withdrawing and -donating substituents on the geometry and activity of the ruthenium complexes and to gain further insight into the trans-cis isomerisation process of the S-chelated complexes. To evaluate the different effects of chelating heteroatoms and to probe electronic effects on sulfur- and nitrogen-chelated latent catalysts, we synthesised a series of novel complexes. These catalysts were compared against two well-known oxygen-chelated initiators and a sulfoxide-chelated complex. The structures of the new complexes have been determined by single-crystal X-ray diffraction and analysed to search for correlations between the structural features and activity. The replacement of the oxygen-chelating atom by a sulfur or nitrogen atom resulted in catalysts that were inert at room temperature for typical ring-closing metathesis (RCM) and cross-metathesis reactions and showed catalytic activity only at higher temperatures. Furthermore, one nitrogen-chelated initiator demonstrated thermo-switchable behaviour in RCM reactions, similar to its sulfur-chelated counterparts.
- Tzur, Eyal,Szadkowska, Anna,Ben-Asuly, Amos,Makal, Anna,Goldberg, Israel,Wozniak, Krzysztof,Grela, Karol,Lemcoff, N. Gabriel
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experimental part
p. 8726 - 8737
(2010/10/19)
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- Sulfur chelated ruthenium compounds useful as olefin metathesis catalysts
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Sulfur chelated ruthenium compounds and methods and compositions involving the same. A method may relate to subjecting an olefin to a metathesis reaction in the presence of a sulfur chelated ruthenium compound. A composition may relate to an olefin starting material dissolved in an organic solvent together with a sulfur chelated ruthenium compound.
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- Correlation analysis of reactivity in the oxidation of substituted benzyl alcohols by morpholinium chlorochromate
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Oxidation of benzyl alcohol and some ortho-, meta- andparo-monosubstitutcd derivatives by morpholinium chlorochromate in dimethyl stilphoxide leads to the formation of corresponding benzaldehydcs. The reaction is first order each in both morpholinium chlorochromate and the alcohol. The reaction is promoted by hydrogen ions; the hydrogen-ion dependence has the form kob8 = a + b [H+]. Oxidation of α,α-dideuteriobenzyl alcohol exhibits a substantial primary kinetic isotope effect (kH/kD = 5.86 at 298 K). The reaction has been studied in nineteen organic solvents and the effect of solvent analysed using Taft's and Swain's multi-parametric equations. The rates of oxidation of para- and meta-substituted benzyl alcohols have been correlated in terms of Charton's tripararnetric LDR equation whereas the oxidation of ortho-substituted benzyl alcohols with tetraperametric LDRS equation. The oxidation of para-substituted benzyl alcohols is more susceptible to the derealization effect than that of ortho- and meta- substituted compounds, which display a greater dependence on the field effect. The positive value of η suggests the presence of an electron-deficient reaction centre in the rate-determining step. The reaction is subjected to steric acceleration by the ortho-substituents. A suitable mechanism is also proposed.
- Soni, Neelam,Tiwari, Vandana,Sharma, Vinita
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scheme or table
p. 669 - 676
(2009/02/08)
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- Correlation analysis of reactivity in the oxidation of substituted benzyl alcohols by 2,2′-bipyridinium chlorochromate
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Oxidation of benzyl alcohol and some ortho-, meta- and para-monosubstituted ones by 2.2′-bipyridinium chlorochromate (BPCC) in DMSO leads to the formation of corresponding benzaldehydes. The reaction is first order in both BPCC and the alcohol. The reaction is promoted by hydrogen ions; the hydrogen-ion dependence has the form : kobs = a + b [H+]. Oxidation of α,α-dideuteriobenzyl alcohol (PhCD2OH) has exhibited a substantial primary kinetic isotope effect (kH/k D = 5.60 at 298 K). The reaction has been studied in nineteen organic solvents and the effect of solvent analysed using Taft's and Swain's multi-parametric equations. The rates of oxidation of para- and meta-substituted benzyl alcohols have been correlated in terms of Charton's triparametric LDR equation whereas the oxidation of ortho-substituted benzyl alcohols with tetraparametric LDRS equation. The oxidation of para-substituted benzyl alcohols is more susceptible to the delocalization effect than that of ortho- and meta-substituted compounds, which display a greater dependence on the field effect. The positive value of η suggests the presence of an electron-deficient reaction centre in the rate-determining step. The reaction is subjected to steric acceleration by the ortho-substituents. A suitable mechanism has been proposed.
- Yajurvedi, Deeksha,Baghmar, Manju,Sharma, Pradeep K.
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body text
p. 496 - 501
(2009/07/18)
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- Latent sulfur chelated ruthenium catalysts: Steric acceleration effects on olefin metathesis
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A series of sulfur chelated dormant ruthenium olefin metathesis catalysts is presented. The catalysts prepared were shown to possess the uncommon cis-dichloro arrangement and were mostly inactive at room temperature. By systematically modifying the size of the substituent groups at the chelating sulfur atom, catalyst activity at different temperatures was significantly affected; more bulky substituents fomented activity at lower temperatures. The catalysts were also shown to be stable in solution and retained their catalytic activity even after being exposed to air for two weeks.
- Kost, Tamar,Sigalov, Mark,Goldberg, Israel,Ben-Asuly, Amos,Lemcoff, N. Gabriel
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p. 2200 - 2203
(2008/09/21)
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- IGF-1R INHIBITOR
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The present invention provides a type I insulin-like growth factor receptor (IGF-1R) inhibitor comprising, as an active ingredient, an indazole derivative represented by Formula (I): {wherein R1 represents -NR4R5 [wherein R4 represents a hydrogen atom or the like, R5 represents substituted or unsubstituted lower alkyl, -C(=O)R6 (wherein R6 represents substituted or unsubstituted lower alkyl, substituted or unsubstituted aryl or the like), or the like], or the like, and R2 and R3 may be the same or different and each represents a hydrogen atom, hydroxy, substituted or unsubstituted lower alkoxy, or the like} or a pharmaceutically acceptable salt thereof, and the like.
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Page/Page column 96
(2008/06/13)
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- Novel thiolated amino-alcohols as chiral ligands for copper-catalyzed asymmetric nitro-aldol reactions
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Thiolated amino-alcohols have been synthesized and evaluated as a potential new class of chiral ligands for copper-catalyzed nitro-aldol reactions. The model nitro-aldol reaction took place smoothly at ambient temperature in the presence of catalytic amounts (5-15 mol %) of the ligands and copper(II) acetate to afford the nitro-aldol product in good to excellent yield without accompanying dehydration. Amino-alcohol ligands bearing N-(2-alkylthio)benzyl substituents provided only modest enantioselectivities (22-46% ee) while those carrying N-2-thienylmethyl substituents provided better enantioselectivities (up to 75% ee). A range of aromatic aldehydes were acceptable for the nitro-aldol reaction with nitromethane, giving moderate to good enantioselectivities (69-88% ee).
- Mansawat, Woraluk,Saengswang, Ittiphol,U-prasitwong, Palita,Bhanthumnavin, Worawan,Vilaivan, Tirayut
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p. 4235 - 4238
(2008/02/08)
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- Correlation analysis of reactivity in the oxidation of substituted benzyl alcohols by quinolinium bromochromate
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Oxidation of benzyl alcohol and some ortho- meta- and para-monosubstituted ones by quinolinium, bromochromate (QBC) in dimethyl sulphoxide (DMSO) leads to the formation of corresponding benzaldehydes. The reaction is first order each in both QBC and the alcohol. The reaction is promoted by hydrogen ions; the hydrogen-ion dependence has the form kobs = a + b [H+]. Oxidation of α,α-dideuteriobenzyl alcohol (PhCD2OH) has exhibited a substantial primary kinetic isotope effect (kH/k D = 5.60 at 298 K). The reaction has been studied in nineteen organic solvents and the effect of solvent analysed using Taft's and Swain's multi-parametric equations. The rates of oxidation of para- and meta-substituted benzyl alcohols have been correlated in terms of Charton's triparametric LDR equation whereas the oxidation of ortho-substituted benzyl alcohols with tetraparametric LDRS equation. The oxidation of para-substituted benzyl alcohols is more susceptible to the delocalization effect than that of ortho- and meta-substituted compounds which display a greater dependence on the field effect. The positive value of η suggests the presence of an electron-deficient reaction centre in the rate-determining step. The reaction is subjected to steric acceleration by the ortho-substituents. A suitable mechanism has been proposed.
- Prakash, Om,Sharma, Pradeep K.
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p. 467 - 473
(2007/10/03)
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- Kinetics and mechanism of the oxidation of substituted benzyl alcohols by [bis(trifluoroacetoxy)iodo]benzene
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The oxidation of substituted benzyl alcohols by bis(trifluoroacetoxy)iodo] benzene in aqueous acetic acid solution results in the formation of the corresponding benzaldehydes. The reaction is first order with respect to each of the alcohol, TFAIB and hydrogen ions. The oxidation of [1,1-2H 2]benzyl alcohol exhibited the presence of a substantial primary kinetic isotope effect, indicating the cleavage of the α-C-H bond in the rate-determining step. Increase in the amount of water, in the solvent mixture of acetic acid and water, results in a decrease of the reaction rate. The analysis of the substituent effect in terms of Charton's LDR equation yielded an excellent correlation with negative reaction constants. A mechanism involving a hydride-ion transfer in the rate-determining step has been proposed.
- Kansara, Alpna,Sharma, Pradeep K.,Banerji, Kalyan K.
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p. 581 - 584
(2007/10/03)
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- Titanium reagents for the synthesis of 2-substituted benzo[b]thiophenes on the solid phase
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Titanium(IV) benzylidenes (Schrock carbenes) bearing a masked sulfur nucleophile in the ortho position were generated from thioacetals with use of low-valent titanocene complex Cp2Ti[P(OEt)3]2 and alkylidenated Merrifield resin-bound esters to give enol ethers. Treatment of the resin-bound enol ethers with a 5:5:90 mixture of TFA, TFAA, and dichloromethane led to cleavage from resin, removal of the tert- butyldimethylsilyl (TBDMS) protecting group, and concomitant cyclization to complete the traceless solid-phase synthesis (SPS) of benzothiophenes. Switching the nature of the linker from acid-stable to acid-sensitive ensured good purity.
- Roberts, Christine F.,Hartley, Richard C.
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p. 6145 - 6148
(2007/10/03)
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- Correlation analysis of reactivity in the oxidation of substituted benzyl alcohols by quinolinium fluorochromate
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Oxidation of benzyl alcohol and some ortho-, meta- and para-monosubstituted ones by quinolinium fluorochromate (QFC) in dimethyl sulphoxide (DMSO) leads to the formation of corresponding banzaldehydes. The reaction is first order each in both QFC and the alcohol. The reaction is promoted by hydrogen ions; the hydrogen-ion dependence has the form kobs= a + b [H+]. Oxidation of α,α-dideuteriobenzyl alcohol (PhCD2OH) has exhibited a substantial primary kinetic isotope effect. The reaction has been studied in nineteen organic solvents and the effect of solvent analysed using Taft's and Swain's multi-parametric equations. The rates of oxidation of para- and meta-substituted benzyl alcohols have been correlated in terms of Charton's triparametric LDR equation, whereas the oxidation of ortho-substituted benzyl alcohols with tetraparametric LDRS equation. The oxidation of para-substituted benzyl alcohols is more susceptible to the delocalization effect than that of ortho- and meta-substituted compounds, which display a greater dependence on the field effect. The positive value of η suggests the presence of an electron-deficient reaction centre in the rate-determining step. The reaction is subjected to steric acceleration by the ortho-substituents. A suitable mechanism has been proposed.
- Dave, Itishri,Sharma, Vinita,Banerji, Kalyan K.
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p. 493 - 499
(2007/10/03)
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- Correlation analysis of reactivity in oxidation of substituted benzyl alcohols by tetrabutylammonium tribromide
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Oxidation of benzyl alcohol and some ortho-, meta- and para-monosubstituted benzyl alcohols by tetrabutylammonium tribromide (TBATB) in aqueous acetic acid leads to the formation of corresponding benzaldehydes. The reaction is first order each in TBATB and the alcohol. The oxidation of [1,1-2H2]benzyl alcohol (PhCD2OH) exhibited a substantial kinetic isotope effect. Addition of tetrabutylammonium chloride or potassium bromide did not affect the rate. Tribromide ion has been postulated as the reactive oxidizing species. The reaction rate increases with increase in the polarity of the solvent. The rates of oxidation of meta- and para-substituted benzyl alcohols showed excellent correlation in terms of Charton's triparametric LDR, equation whereas the oxidation of ortho-substituted benzyl alcohols correlated best with the LDRS equation. The oxidation of para-substituted benzyl alcohols is more susceptible to the delocalization effect than is the oxidation of ortho- and meta-substituted compounds, which display a greater dependence on the field effect. The positive value of η suggests the presence of an electron-deficient reaction centre in the rate-determining step. The reaction is subject to steric acceleration by the ortho-substituents. A suitable mechanism is proposed. Copyright
- Kumar, Ashok,Sharma, Pradeep K.,Banerji, Kalyan K.
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p. 721 - 727
(2007/10/03)
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- Kinetics and Mechanism of the Oxidation of Substituted Benzyl Alcohol by Oxo(salen)manganese(V) Complexes
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The oxidation of monosubstituted benzyl alcohols by substituted oxo(salen)manganese(V) complexes, in acetonitrile, leads to the formation of the corresponding benzaldehydes. The reaction is first order with respect to both the alcohol and the Mn(V) complex. The oxidation of [1,1-2H2]benzyl alcohol exhibited the presence of a substantial kinetic isotope effect. The rate of oxidation of alcohols by four Mn(V) complexes have been determined. The rates of the oxidation of meta-substituted benzyl alcohols correlated best with Taft's ?1 and ?R0 constants. The para-substituted compounds exhibited excellent correlation with ?1 and ?R+ values. The ortho-substituted alcohols correlated well in terms of Charton's triparametric equation. The polar reaction constants are negative. The ortho- compounds showed a steric acceleration of the reaction. The rate of reduction of the substituted Mn(V) complexes showed an excellent correlation in terms of Hammett equation with positive reaction constants. The reactivity-selectivity principle (RSP) is obeyed in this reaction. The validity of RSP has been verified by Exner's mathematical procedure. Suitable mechanism have been discussed.
- Kumbhat, Vinita,Sharma, Pradeep K.,Banerji, Kalyan K.
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p. 562 - 585
(2007/10/03)
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- Correlation analysis of reactivity in oxidation of substituted benzyl alcohols by benzyltrimethylammonium chlorobromate
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Oxidation of benzyl alcohol and some ortho-, meta- and para-monosubstituted benzyl alcohols by benzyltrimethylammonium chlorobromate (BTMACB) in aqueous acetic acid leads to the formation of corresponding benzaldehydes. The reaction is first order each in BTMACB and the alcohol. The oxidation of α,α-dideuteriated benzyl alcohol (PhCD2OH) exhibits a substantial kinetic isotope effect. Addition of benzyltrimethylammonium chloride or potassium bromide ions does not affect the rate. Chlorobromate ion has been postulated as the reactive oxidizing species. The effect of solvent composition indicates that the reaction rate increases with an increase in the polarity of the solvent. The rates of oxidation of meta- and para-substituted benzyl alcohols have been correlated in terms of Charton's triparametric LDR equation whereas the oxidation of ortho-substituted benzyl alcohols has been correlated with tetraparametric LDRS equation. The oxidation of para-substituted benzyl alcohols is more susceptible to the delocalization effect than is the oxidation of ortho- and meta-substituted compounds, which display a greater dependence on the field effect. The positive value of η suggests the presence of an electron-deficient reaction centre in the rate-determining step. The reaction is subjected to steric acceleration by the ortho-substituents. A suitable mechanism has been proposed.
- Sita Rama Raju,Sharma,Banerji
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p. 1258 - 1263
(2007/10/03)
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- Correlation Analysis of Reactivity in the Oxidation of Substituted Benzyl Alcohols by Benzyltrimethylammonium Tribromide
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Oxidation of benzyl alcohol and some ortho-, meta- and para- monosubstituted benzyl alcohols by benzyltrimethylammonium tribromide (BTMAB) in aqueous acetic acid leads to the formation of corresponding benzaldehydes. The reaction is first order with respect to both BTMAB and the alcohol. The oxidation of deuteriated benzyl alcohol exhibited a substantial kinetic isotope effect. Addition of benzyltrimethylammonium or bromide ions did not affect the rate. Tribromide ion has been postulated as the reactive oxidizing species. The rates of the oxidation of para- and meta-substituted benzyl alcohols were correlated with Taft's and Swain's field and resonance substituent constants. The oxidation of para-substituted benzyl alcohols showed excellent correlation with Taft's ?1 and ?RBA values; the meta-compounds correlated best with ?1 and ?R0 values. Rates of the ortho-substituted compounds showed a significant correlation with Charton's triparametric equation. Suitable mechanism has been proposed.
- Anjana,Kothari, Seema,Banerji, Kalyan K.
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p. 2118 - 2135
(2007/10/03)
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- Correlation analysis of reactivity in the oxidation of substituted benzyl alcohols by benzyltrimethylammonium dichloroiodate
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Oxidation of benzyl alcohols by benzyltimethylammonium dichloroiodate (BTMACI) in glacial acetic acid, in the presence of zinc chloride, resulted in the formation of corresponding benzaldehydes. The reaction is first order with respect to BTMACI, the alcohol and zinc chloride. The oxidation of α,α-dideuteriobenzyl alcohol exhibited a primary kinetic isotope effect (ko/kD=5.21 at 318 K). Addition of benzyltrimethylammonium chloride enhances the reaction rate. It is proposed that the reactive oxidizing species is + -. The rate constants of oxidation were subjected to correlation analysis using various single- and multi-parametric equations. The best correlation is obtained with Charton's LDR and LDRS equations. The polar regression coefficients are negative, indicating the formation of a cationic species in the rate-determining step. The reaction is subject to steric acceleration by ortho-substituent. A mechanism involving a hydride-ion transfer from the alcohol to the oxidant in the rate-determining step has been postulated.
- Rao, P. Surya Chandra,Suri, Deepa,Kothari, Soona,Banerji, Kalyan K.
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p. 2251 - 2272
(2007/10/03)
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- Correlation analysis of structure and reactivity in the oxidation of substituted benzyl alcohols by bis(2,2' -bipyridyl) copper(II) permanganate
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The oxidation of substituted benzyl alcohols by bis(2,2'-bipyridyl) copper(II) permanganate (BBCP), leading to the corresponding benzaldehydes is first-order with respect to BBCP. Michaelis-Menten type kinetics were observed with respect to the alcohols. The oxidation of a a-dideuteriobenzyl alcohol indicated the presence of a substantial kinetic isotope effect. The rates of oxidation of meta- and para-substituted benzyl alcohols were correlated in terms of Charton's triparametric LDR equation whereas ortho-substituted benzyl alcohols were correlated with a four parametric LDRS equation. The results of correlation analyses point to an electron-deficient reaction center in the transition state.
- Vyas,Kothari,Banerji
-
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- Correlation analysis of reactivity in the oxidation of substituted benzyl alcohols by pyridinium bromochromate
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The rates of the oxidation of para- and meta-substituted benzyl alcohols by pyridinium bromochromate have been obtained in DMSO and correlated with Taft's and Swain's field and resonance substituent constants.The oxidation of para-substituted benzyl alcohols show excellent correlation with Taft's ?I and ?BAR values; the meta-substituted compounds correlate best with ?I and ?OR values.Rates of the ortho-substituted compounds show significant correlation with Charton's triparametric equation.The reaction is of second order, first with respect to theeach reactant.The reaction is promoted by hydrogen ions; the hydrogen-ion dependence has the form kobs = a+b+>.The oxidation exhibited a substantial primary kinetic isotope effect.The reaction has been studied in nineteen organic solvents and the effect of solvent analysed using Taft's and Swain's multiparametric equations.Suitable mechanism has been proposed.
- Pareek, Arun,Kothari, Seema,Banerji, Kalyan K.
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p. 968 - 974
(2007/10/03)
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- Correlation Analysis of Reactivity in the Oxidation of Substituted Benzyl Alcohols by Pyridinium Hydrobromide Perbromide
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Oxidation of monosubstituted benzyl alcohols by pyridinium hydrobromide perbromide (PHPB) leads to the formation of the corresponding benzaldehydes.The reaction is first order with respect to PHPB.Michaelis-Menten-type kinetics were observed with respect to he alcohol.The oxidation of α,α-dideuteriobenzyl alcohol indicated the presence of a substantial kinetic isotope effect.The rates of oxidation of meta- and para-substituted benzyl alcohols were correlated in terms of Taft's and Swain's dual substituent-parameter equations.The rates of the meta compounds correlated best with Taft's ?1 and ?0R values whereas the para-compounds showed an excellent correlation with Taft's ?1 and ?R + constants.The rates of the otho-substituted alcohols showed very good correlation with Charton's triparametric equation.The rate increased with an increase in the polarity of the solvent.A mechanism involving a rapid reversible formation of an intermediate complex and its subsequent decomposition in the rate-determining step has been proposed.
- Suri, Deepa,Banerji, Kalyan K.,Kothari, Seema
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p. 1734 - 1758
(2007/10/03)
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- Oxidation of Substituted Benzyl Alcohols by Pyridinium Fluorochromate: A Kinetic Study
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The kinetics of the oxidation of 30 monosubstituted benzyl alcohols to the corresponding benzaldehydes by pyridinium fluorochromate (PFC) have been studied.The reaction is first order with respect to PFC.A Michaelis-Menten type kinetics was observed with respect to the substrate, indicating the formation of a PFC-alcohol complex in the preequilibrium.The formation constants and the rates of disproportionation of the complexes were determined.The oxidation of benzyl alcohol indicated the presence of a substantial primary kinetic isotope effect.The ratesof the decomposition of the complexes of the meta-and para-substituted alcohols were analyzed in terms of Taft's and Swain's dual substituent parameter equations.The meta compounds showed an excellent correlation with Taft's ?I and ?R0 values while the para-substituted compounds correlate with ?1 and ?RBA constants.The rates of the ortho-substituted alcohols correlate with Charton's equation of inductive, resonance, and steric paramaters.The reaction was studied in 19 solvents.The correlation analysis of the solvent effect indicated the greater importance of the cation-solvating power of the solvent.The reaction involves a hydride ion transfer in the rate-determining step.
- Banerji, Kalyan K.
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p. 2154 - 2159
(2007/10/02)
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- Separation of Polar and Steric Effects in Oxidation of ortho-Substituted Benzyl Alcohols by Acid Permanganate
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The kinetics of the oxidation of ten ortho-substituted benzyl alcohols by acid permanganate have been studied.The reaction is first order each with respect to , and .The correlation of the rates of oxidation with Charton's extended Hammett equation, involving inductive, resonance and steric parameters, is excellent.The polar reaction constants have negative values.The reaction is subject to steric acceleration by the ortho-substituents.The mechanistic aspects are discussed.
- Mathur, Sandhya,Gupta, Anita,Banerji, Kalyan K.
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p. 581 - 583
(2007/10/02)
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- Chemistry of 8-Substituted 1-Naphtylmethylenes and 2-Substituted Benzylidenes. A simple Entry to 1H-Cyclobutanaphthalenes
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Study has been made of neighobing heteroatom interaction in thermolysis and photolysis of proximally substituted aryldiazomethanes.Thus, (8-bromo-1-naphthyl)diazomethane (1c) isomerize at 132 deg C to 9-bromo- (18a), 9-iodo- (18b), and 6,9-dichloro-3H-benzindazoles (18c).Indazoles 18a and 18b are reduced by lithium aluminum hydride to 3H-benzindazole (21), identical with that from decomposition of N-(1-methyl-2-naphthyl)-N-nitrosoacetamide (19). 1-Naphthyldiazomethane (1e) does not isomerize however to 21; in benzene at -78 deg c, 1e converts to trans-bis(1-naphthyl)ethylene (22b), 1-naphthalzine (26), and 7-(1-naphthyl)cycloheptatriene (24) wich rearranges to 1-(1-naphthyl)cycloheptatriene (25) whean heated.Irradiation of 1a in ethyl ether results in trans-bis(8-bromo-1-naphthyl)ethylene (22c) and 1-bromo-1Hcyclobutanaphthalene (4a), the first aryne bridged in its peri positions by a single carbon atom moiety.Aqueous silver nitrate converts 4a tp 1H-cyclobutanaphthyl nitrate (4b) and 1-naphthaldehyde (28), presumably by ring opening of 1-hydroxy-1H-cyclobutanaphhtalene (27).Reaction of 4a with magnesium and hydrolysis of the resulting Grignard reagent yield 1H-cyclobutanaphthalene (4d), a hydrocarbon acid wich udergoes deuterium exchange at C-1 considerably slower than to acenaphthene (29) and diphenylmethane (30).Thermolysis and photolysis of diazomethane (1d) to give 2-methyl-2H-naphthothiophene (33) are of note in that methylthio participation in 8-(methylthio)-1-naphthylidene (2d) and thia-Stevens rearrangement appear to be involved. (o-Iodophenyl)diazomethane (5a) thermolyzes to trans-bis(o-iodophenyl)ethylene and o-iodobenzalazine (36); products of reaction of the iodine moiety with the carbenic center in o-iodobenzylidene (6a) were not found.Thermolysis however of (o-(methylthio)phenyl)diazpmethane (5b) results in inrtamolecular C-H insertion to yield 4,5-dihydrothiophene (37) along with trans-bisethylene (38) and o-(methylthio)benzalazine(39).Intermolecular carbenic interception does occur in photolysis of 5b iin that 2-(2-ethoxy-1-propyl)thioanisole (40) is formed along with 398 and 39.The mechanisms of the various participation processes in the above substituted 1-naphthylidenes are discussed.
- Bailey, R. J.,Card, P. J.,Shechter, H.
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p. 6096 - 6103
(2007/10/02)
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- Synthesis of S-Substituted Benzils and Some Hindered Biphenyls
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Three methylthio and/or methylsulfinyl substituted benzils (2, 6 and 7) have been synthesized on photo- or thermochemical routes, respectively.Photodecarboxylation of some new different substituted mesityl benzoates (1a-e) leads to hindered biphenyls (3a-e) accompanied sometimes by aldehyde (4a-c) and benzil formation (2) due to compatitive α-cleavage and subsequent stabilization processes of such generated free aroyl radicals.A short summary on constitutional conditions for intramolecular photoredox reactions of ortho functionalized aryl sulfinyl compounds is presented. - Keywords: Photodecarboxylations, α-Cleavages, Photoredox Reactions, Sulfoxides
- Luedersdorf, Reinhard,Mai, Juergen,Praefcke, Klaus
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p. 1420 - 1425
(2007/10/02)
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- ORGANISCHE PHOTOCHEMIE XXXII Beitrag ueber Photoreaktionen von Aroyl-diphenylphosphinen in Loesung
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Three new examples to photoreactions of aroyl diphenyl phosphines which undergo α-cleavage as well as 1,2-oxygen transfer from the carbonyl group onto the phosphorous atom are described.Both reactions also occur in the mass spectrometer.
- Dankowski, Manfred,Praefcke, Klaus
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p. 105 - 108
(2007/10/02)
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