- Enhancement of the Oxidizing Power of an Oxoammonium Salt by Electronic Modification of a Distal Group
-
The multigram preparation and characterization of a novel TEMPO-based oxoammonium salt, 2,2,6,6-tetramethyl-4-(2,2,2-trifluoroacetamido)-1-oxopiperidinium tetrafluoroborate (5), and its corresponding nitroxide (4) are reported. The solubility profile of 5 in solvents commonly used for alcohol oxidations differs substantially from that of Bobbitt's salt, 4-acetamido-2,2,6,6-tetramethyl-1-oxopiperidinium tetrafluoroborate (1). The rates of oxidation of a representative series of primary, secondary, and benzylic alcohols by 1 and 5 in acetonitrile solvent at room temperature have been determined, and oxoammonium salt 5 has been found to oxidize alcohols more rapidly than does 1. The rate of oxidation of meta- and para-substituted benzylic alcohols by either 1 or 5 displays a strong linear correlation to Hammett parameters (r > 0.99) with slopes (ρ) of -2.7 and -2.8, respectively, indicating that the rate-limiting step in the oxidations involves hydride abstraction from the carbinol carbon of the alcohol substrate.
- Lambert, Kyle M.,Stempel, Zachary D.,Kiendzior, Sadie M.,Bartelson, Ashley L.,Bailey, William F.
-
-
Read Online
- Katalytische Reduktion von aromatischen Carbonsaeurefluoriden zu Aldehyden
-
Aromatic acyl fluorides can be reduced to the corresponding aldehydes in the presence of palladium complexes.Polymethylhydrosiloxane (PMHS) gives better results than hydrogen.
- Braden, Rudolf,Himmler, Thomas
-
-
Read Online
- Photooxidation of Benzyl Alcohols Sensitized by TiO2 in CH3CN in the Presence of Ag2SO4. Kinetic Evidence for the Involvement of Adsorption Phenomena
-
X-Ring substituted benzyl alcohols are photooxidized to the corresponding aldehydes by TiO2 in CH3CN in the presence of Ag2SO4 and kinetic evidence suggests a changeover of the electron abstraction site from the aromatic moiety (X = 4-CH3O, 4-CH3, 4-Cl, H, 3-Cl) to the hydroxylic group (X = 3-CF3, 4-CF3), probably owing to the preferential adsorption of OH on TiO2.
- Amori, Laura,Del Giacco, Tiziana,Rol, Cesare,Sebastiani, Giovanni V.
-
-
Read Online
- Oxidative C-S Bond Cleavage of Benzyl Thiols Enabled by Visible-Light-Mediated Silver(II) Complexes
-
The oxidative cleavage reaction of the C-S bond using singlet oxygen is challenging because of its uncontrollable nature. We have developed a novel method for the singlet-oxygen-mediated selective C-S bond cleavage reaction using silver(II)-ligand complexes. Visible-light-induced silver catalysis enables the controlled oxidative cleavage of benzyl thiols to afford carbonyl compounds, such as aldehydes or ketones, which are important synthetic components.
- Hong, Boseok,Aganda, Kim Christopher C.,Lee, Anna
-
supporting information
p. 4395 - 4399
(2020/06/05)
-
- Cerium(IV) Carboxylate Photocatalyst for Catalytic Radical Formation from Carboxylic Acids: Decarboxylative Oxygenation of Aliphatic Carboxylic Acids and Lactonization of Aromatic Carboxylic Acids
-
We found that in situ generated cerium(IV) carboxylate generated by mixing the precursor Ce(OtBu)4 with the corresponding carboxylic acids served as efficient photocatalysts for the direct formation of carboxyl radicals from carboxylic acids under blue light-emitting diodes (blue LEDs) irradiation and air, resulting in catalytic decarboxylative oxygenation of aliphatic carboxylic acids to give C-O bond-forming products such as aldehydes and ketones. Control experiments revealed that hexanuclear Ce(IV) carboxylate clusters initially formed in the reaction mixture and the ligand-to-metal charge transfer nature of the Ce(IV) carboxylate clusters was responsible for the high catalytic performance to transform the carboxylate ligands to the carboxyl radical. In addition, the Ce(IV) carboxylate cluster catalyzed direct lactonization of 2-isopropylbenzoic acid to produce the corresponding peroxy lactone and ?3-lactone via intramolecular 1,5-hydrogen atom transfer (1,5-HAT).
- Hirosawa, Keishi,Mashima, Kazushi,Satoh, Tetsuya,Shinohara, Koichi,Shirase, Satoru,Tamaki, Sota,Tsurugi, Hayato
-
supporting information
(2020/03/25)
-
- Organophotoredox-Mediated Amide Synthesis by Coupling Alcohol and Amine through Aerobic Oxidation of Alcohol
-
The combination of an organic photocatalyst [4CzIPN (1,2,3,5-tetrakis(carbazol-9-yl)-4,6 dicyanobenzene) or 5MeOCzBN (2,3,4,5,6-pentakis(3,6-dimethoxy-9 H-carbazol-9-yl)benzonitrile)], quinuclidine, and tetra-n-butylammonium phosphate (hydrogen-bonding catalyst) was employed for amide bond formations. The hydrogen-bonded OH group activated the adjacent C?H bond of alcohols towards hydrogen atom transfer (HAT) by a radical species. The quinuclidinium radical cation, generated through single-electron oxidation of quinuclidine by the photocatalyst, employed to abstract a hydrogen atom from the α-C?H bond of alcohols selectively due to a polarity effect-produced α-hydroxyalkyl radical, which subsequently converted to the corresponding aldehyde under aerobic conditions. Then the coupling of the aldehyde and an amine formed a hemiaminal intermediate that upon photocatalytic oxidation produced the amide.
- Samanta, Samya,Shah, Sk. Sheriff,Shee, Maniklal,Singh, Amit Kumar,Singh, N. D. Pradeep,Venkatesh, Yarra
-
supporting information
(2020/03/05)
-
- Method for synthesizing aromatic aldehyde through iron catalyzed oxidation allyl aromatic compound
-
The invention discloses a method for synthesizing aromatic aldehyde through an iron catalyzed oxidation allyl aromatic compound. According to the specific method, under the promotion effect of hydrogen silane, with air or oxygen as the oxidant, the aromatic aldehyde compound is synthesized through the iron catalyzed oxidation allyl aromatic compound, the reaction temperature is 20-150 DEG C, and the time is 0.25-60 h. The method has the advantages that a catalyst source is wide, the price is low and the environment is protected; an oxidant source is wide, the price is low and no waste is generated; the reaction conditions are mild, selectivity is high and the yield is high; a substrate source is wide and stable; a substrate functional group is high in compatibility and a substrate is widein application range; complicated small molecules are compatible and can be well converted into aldehyde. The target product separation yield can reach up to 96% under the optimized reaction conditions.
- -
-
Paragraph 0102-0104; 0151
(2019/06/27)
-
- AN IMPROVED PROCESS FOR PREPARATION OF TRIFLUOROMETHYLBENZALDEHYDES AND INTERMEDIATES THEREOF
-
The present invention provides an in-situ process for preparation of a compound of formula 1 and intermediate thereof, These compounds are useful chemical intermediates for the production of pesticides and pharmaceutical products.
- -
-
-
- An Engineered Alcohol Oxidase for the Oxidation of Primary Alcohols
-
Structure-guided directed evolution of choline oxidase has been carried out by using the oxidation of hexan-1-ol to hexanal as the target reaction. A six-amino-acid variant was identified with a 20-fold increased kcat compared to that of the wild-type enzyme. This variant enabled the oxidation of 10 mm hexanol to hexanal in less than 24 h with 100 % conversion. Furthermore, this variant showed a marked increase in thermostability with a corresponding increase in Tm of 20 °C. Improved solvent tolerance was demonstrated with organic solvents including ethyl acetate, heptane and cyclohexane, thereby enabling improved conversions to the aldehyde by up to 30 % above conversion for the solvent-free system. Despite the evolution of choline oxidase towards hexan-1-ol, this new variant also showed increased specific activities (by up to 100-fold) for around 50 primary aliphatic, unsaturated, branched, cyclic, benzylic and halogenated alcohols.
- Heath, Rachel S.,Birmingham, William R.,Thompson, Matthew P.,Taglieber, Andreas,Daviet, Laurent,Turner, Nicholas J.
-
p. 276 - 281
(2019/01/04)
-
- A Simple, Mild and General Oxidation of Alcohols to Aldehydes or Ketones by SO2F2/K2CO3 Using DMSO as Solvent and Oxidant
-
A practical, general and mild oxidation of primary and secondary alcohols to carbonyl compounds proceeds in yields of up to 99% using SO2F2 as electrophile in DMSO as both the oxidant and the solvent at ambient temperature. No moisture- and oxygen-free conditions are required. Stoichiometric amount of inexpensive K2CO3, which generates easy to separate by-products, is used as the base. Thus, 5-gram scale runs proceeded in nearly quantitative yields by a simple filtration as the work-up. The use of a polar solvent such as DMSO, which usually promotes competing Pummerer rearrangement, is also noteworthy. This protocol is compatible with a variety of common N-, O-, and S-functional groups on (hetero)arene, alkene and alkyne substrates (68 examples). The protocol was applied (99% yield) to a formal synthesis of the important cholesterol-lowering drug Rosuvastatin. (Figure presented.).
- Zha, Gao-Feng,Fang, Wan-Yin,Leng, Jing,Qin, Hua-Li
-
supporting information
p. 2262 - 2267
(2019/04/17)
-
- A Transition-Metal-Free One-Pot Cascade Process for Transformation of Primary Alcohols (RCH2OH) to Nitriles (RCN) Mediated by SO2F2
-
A new transition-metal-free one-pot cascade process for the direct conversion of alcohols to nitriles was developed without introducing an “additional carbon atom”. This protocol allows transformations of readily available, inexpensive, and abundant alcohols to highly valuable nitriles.
- Jiang, Ying,Sun, Bing,Fang, Wan-Yin,Qin, Hua-Li
-
supporting information
p. 3190 - 3194
(2019/05/21)
-
- Oxidation of Alcohols to Carbonyl Compounds Catalyzed by Oxo-Bridged Dinuclear Cerium Complexes with Pentadentate Schiff-Base Ligands under a Dioxygen Atmosphere
-
Ionic mononuclear and neutral dinuclear complexes of cerium(III) 3-L1-3-L9 bearing a series of dianionic pentadentate Schiff-base ligands were synthesized, characterized, and used as catalysts for N-oxyl radical-free aerobic alcohol oxidation. Reactions of Ce(NO3)3·6H2O with o-tert-butyl-substituted sterically hindered ligands NH(CH2CH2-Rfnet=CHC6H2-3-(tBu)-5-R2-2-OH)2 (for L1H2, R2 = tBu; for L2H2, R2 = OMe; and for L3H2, R2 = H) in the presence of triethylamine afforded the corresponding anionic cerium complexes [HNEt3][Ce(L1-3)(NO3)2] (3-L1-3-L3), whereas complexation with sterically less hindered ligands, such as NH(CH2CH2N=CHC6H2-3-R1-5-R2-2-OH)2 (for L4H2, R1 = OMe and R2 = H; for L5H2, R1 = H and R2 = tBu; for L6H2, R1 = H and R2 = OMe; for L7H2, R1 = H and R2 = H; for L8H2, R1 = H and R2 = NO2; and for L9H2, R1 = tBu and R2 = NO2), afforded neutral dinuclear complexes [Ce(L4-9)(NO3)]2 (3-L4-3-L9). Among these newly prepared complexes, complex 3-L1 was selected as the best catalyst for oxidizing primary and secondary alcohols under a dioxygen atmosphere without any N-oxyl radicals such as TEMPO to produce the corresponding carbonyl compounds, where the oxo-bridged dinuclear complex worked as a catalyst while maintaining its dinuclear skeleton during the catalytic cycle. In addition, an intramolecular redox process between the two cerium centers through the bridging oxygen atom played a key role in forming the ligand phenoxide radical-mediated TEMPO-free alcohol oxidation reaction.
- Shirase, Satoru,Shinohara, Koichi,Tsurugi, Hayato,Mashima, Kazushi
-
p. 6939 - 6947
(2018/06/25)
-
- Correlation analysis of reactivity in the oxidation of substituted benzyl alcohols by benzimidazolium dichromate - A kinetic and mechanistic aspects
-
The oxidation of a number of para- and meta-substituted benzyl alcohols by benzimidazolium dichromate (BIDC), in dimethyl sulphoxide, leads to the formation of the corresponding benzaldehydes. The reaction is first order with respect to each BIDC and alcohol. The reaction is catalyzed by hydrogen ions and the dependence has the form kobs = a + b[H+]. The oxidation of [1,1-2H2]benzyl alcohol exhibited the presence of a substantial kinetic isotope effect. The rates of the oxidation of meta-substituted benzyl alcohols correlated best with Taft's σ1 and σR0 constants. The para-substituted compounds exhibited excellent correlation with σ1 and σRBA values. The polar reaction constants are negative. The rate of oxidation of benzyl alcohol was determined in nineteen organic solvents. An analysis of the solvent effect by multiparametric equations indicated the greater importance of the cation-solvating power of the solvents. Suitable mechanisms have been discussed.
- Kumar, Pravesh,Panday, Dinesh,Kothari, Seema
-
p. 1207 - 1215
(2020/06/27)
-
- One-pot two-step conversion of aromatic carboxylic acids and esters to aromatic aldehydes via indium-catalyzed reductive thioacetalization and desulfurization
-
Described herein is that a new approach to a one-pot two-step conversion of aromatic carboxylic acids/esters to aromatic aldehydes, in which indium(III) iodide effectively catalyzes both the first reductive thioacetalization of carboxylic acids and a subsequent desulfurization of the in-situ formed thioacetal intermediates leading to aldehydes.
- Sakai, Norio,Minato, Kohei,Ogiwara, Yohei
-
supporting information
p. 4563 - 4567
(2017/11/03)
-
- Cerium peroxo complex (by machine translation)
-
[A] is soluble in organic solvents, alcohol oxidation catalyst cerium peroxo complex can be used. Cerium peroxo complex [a], cerium, N, N ' - bis ([sarichiriden[sarichiriden]) diethylenetriamine backbone with the ligand. N, N ' - bis ([sarichiriden[sarichiriden]) diethylenetriamine backbone, substituted alkyl groups with aromatic substitutions at position 2 and 4. The, the ligands of the peroxo groups, two cerium atoms are linked 2. [Drawing] no (by machine translation)
- -
-
Paragraph 0027; 0028
(2017/12/01)
-
- Dual Catalysis for the Aerobic Oxidation of Benzyl Alcohols – Nitric Acid and Fluorinated Alcohol
-
Benzyl alcohols were oxidized with oxygen to aldehydes in excellent yields with high selectivities at room temperature. Dual catalysis was operative with HNO3as the oxidant and precursor of the nitrogen oxides and with the use of 1,1,1,3,3,3-hexafluoro-2-propanol as a template catalyst and solvent. Fluorinated alcohols also increased the selectivity by inhibiting further oxidation to benzoic acids. Activation of nitric acid catalyzed aerobic oxidation by the fluorinated solvent made the use of 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) or a metal catalyst superfluous.
- Mo?ina, ?tefan,Stavber, Stojan,Iskra, Jernej
-
supporting information
p. 448 - 452
(2017/02/05)
-
- Nitrogen dioxide-catalyzed aerobic oxidation of benzyl alcohols under cocatalyst and acid-free conditions
-
Nitrogen dioxide is usually considered as a mediator between dioxygen and the catalysts for the aerobic oxidation of alcohols. Here, we report that nitrogen dioxide has an ability to catalyze this reaction, which not only avoids the use of the cocatalysts or the acids in traditional approaches, but also reveals a method for the present transformation with a single component catalyst. A series of primary and secondary benzyl alcohols underwent this transformation to give the targeted products in low to high yields.
- Ren, Fangping,Tian, Xinzhe,Ren, Yun-Lai,Zhao, Shuang,Wang, Jianji,Zhao, Bo
-
-
- Trifluoromethylation of (hetero)aryl iodides and bromides with copper(i) chlorodifluoroacetate complexes
-
A new copper-mediated trifluoromethylation reaction using copper(i) chlorodifluoroacetate complexes as reagents is reported. The complex [L2Cu][O2CCF2Cl] (L = bpy, dmbpy, phen) reacted with (hetero)aryl iodides and bromides in the presence of CsF in DMF at 75 °C to afford the trifluoromethylarenes in good to excellent yields. High compatibility with various chemical functions or (hetero)cycles was also observed in the reaction. A reaction mechanism involving a difluorocarbene intermediate, along with a subsequent formation of a -CF3 anion was proposed.
- Lin, Xiaoxi,Li, Zhengyu,Han, Xiaoyan,Weng, Zhiqiang
-
p. 75465 - 75469
(2016/08/24)
-
- Decarboxylative Trifluoromethylating Reagent [Cu(O2CCF3)(phen)] and Difluorocarbene Precursor [Cu(phen)2][O2CCF2Cl]
-
This article describes the new economic decarboxylative trifluoromethylating reagent [Cu(phen)(O2CCF3)] (1; phen=1,10-phenanthroline) and the efficient difluorocarbene precursor [Cu(phen)2][O2CCF2Cl] (2). Treatment of copper tert-butoxide with phen and subsequent addition of trifluoroacetic acid or chlorodifluoroacetic acid afforded air-stable complexes 1 and 2, respectively, which were characterized by X-ray crystallography. The copper(I) ion in 1 is coordinated by a bidentate phen ligand, a monodentate trifluoroacetate group, and a molecule of CH3CN in a distorted tetrahedral coordination geometry. The molecular structure of 2 adopts an ionic form that consists of a [Cu(phen)2]+ cation and a chlorodifluoroacetate anion. Complex 1 reacted with a variety of aryl and heteroaryl halides to form trifluoromethyl (hetero)arenes in good yields. The corresponding Hammett plot exhibited a linear relationship and a reaction parameter (ρ)=+0.56±0.02, which indicated that the trifluoromethylation reaction proceeded via a nucleophilic reactive species. Complex 2 reacts with phenols to produce aryl difluoromethyl ethers in modest-to-excellent yields. Mechanistic investigations revealed that the difluoromethylation reaction proceeds by initial copper-mediated formation of difluorocarbene and subsequent concerted addition of difluorocarbene to the phenol to form a three-center transition state.
- Lin, Xiaoxi,Hou, Chuanqi,Li, Haohong,Weng, Zhiqiang
-
supporting information
p. 2075 - 2084
(2016/02/12)
-
- Cerium-Complex-Catalyzed Oxidation of Arylmethanols under Atmospheric Pressure of Dioxygen and Its Mechanism through a Side-On μ-Peroxo Dicerium(IV) Complex
-
A new CeIV complex [Ce{NH(CH2CH2N=CHC6H2-3,5-(tBu)2-2-O)2}(NO3)2] (1), bearing a dianionic pentadentate ligand with an N3O2 donor set, has been prepared by treating (NH4)2Ce(NO3)6 with the sodium salt of ligand L1. Complex 1 in the presence of TEMPO and 4 ? molecular sieves (MS4 A) has been found to serve as a catalyst for the oxidation of arylmethanols using dioxygen as an oxidant. We propose an oxidation mechanism based on the isolation and reactivity study of a trivalent cerium complex [Ce{NH(CH2CH2N=CHC6H2-3,5-(tBu)2-2-O)2}(NO3)(THF)] (2), its side-on μ-O2 adduct [Ce{NH(CH2CH2N=CHC6H2-3,5-(tBu)2-2-O)2}(NO3)]2(μ-η2:η2-O2) (3), and the hydroxo-bridged CeIV complex [Ce{NH(CH2CH2N=CHC6H2-3,5-(tBu)2-2-O)2}(NO3)]2(μ-OH)2 (4) as key intermediates during the catalytic cycle. Complex 2 was synthesized by reduction of 1 with 2,5-dimethyl-1,4-bis(trimethylsilyl)-1,4-diazacyclohexadiene. Bubbling O2 into a solution of 2 resulted in formation of the peroxo complex 3. This provides the first direct evidence for cerium-catalyzed oxidation of alcohols under an O2 atmosphere. Cerium-catalyzed alcohol oxidation: A new CeIV complex [Ce{NH(CH2CH2N=CHC6H2-3,5-(tBu)2-2-O)2}(NO3)2] (1) has been shown to serve as a catalyst for the oxidation of arylmethanols using dioxygen as an oxidant in the presence of TEMPO and molecular sieves MS4 A (see scheme). CeIII complex 2, obtained by reduction of 1 with 2,5-dimethyl-1,4-bis(trimethylsilyl)-1,4-diazacyclohexadiene, reacted with O2 to give the peroxo complex 3. This provides the first direct evidence for operation of the peroxo mechanism in the cerium-catalyzed oxidation of alcohols under O2 atmosphere.
- Paul, Mitali,Shirase, Satoru,Morimoto, Yuma,Mathey, Laurent,Murugesapandian, Balasubramanian,Tanaka, Shinji,Itoh, Shinobu,Tsurugi, Hayato,Mashima, Kazushi
-
p. 4008 - 4014
(2016/03/16)
-
- Simple and Efficient Ruthenium-Catalyzed Oxidation of Primary Alcohols with Molecular Oxygen
-
Oxidative transformations utilizing molecular oxygen (O2) as the stoichiometric oxidant are of paramount importance in organic synthesis from ecological and economical perspectives. Alcohol oxidation reactions that employ O2are scarce in homogeneous catalysis and the efficacy of such systems has been constrained by limited substrate scope (most involve secondary alcohol oxidation) or practical factors, such as the need for an excess of base or an additive. Catalytic systems employing O2as the “primary” oxidant, in the absence of any additive, are rare. A solution to this longstanding issue is offered by the development of an efficient ruthenium-catalyzed oxidation protocol, which enables smooth oxidation of a wide variety of primary, as well as secondary benzylic, allylic, heterocyclic, and aliphatic, alcohols with molecular oxygen as the primary oxidant and without any base or hydrogen- or electron-transfer agents. Most importantly, a high degree of selectivity during alcohol oxidation has been predicted for complex settings. Preliminary mechanistic studies including18O labeling established the in situ formation of an oxo–ruthenium intermediate as the active catalytic species in the cycle and involvement of a two-electron hydride transfer in the rate-limiting step.
- Ray, Ritwika,Chandra, Shubhadeep,Maiti, Debabrata,Lahiri, Goutam Kumar
-
supporting information
p. 8814 - 8822
(2016/07/06)
-
- Safe and convenient nitroxyl radical and imide dual catalyzed NaOCl oxidation of alcohols to aldehydes/ketones
-
A novel and practical oxidation of alcohols to carbonyl compounds using NaOCl in the presence of catalytic amounts of imide compound and nitroxyl radical has been developed. A wide variety of aliphatic, benzylic primary alcohols, and secondary alcohols were oxidized to afford the corresponding aldehydes and ketones in up to 98% yield without undesired halogenation on aromatic rings or double bonds. The oxidation safely proceeded not only in the presence of K2CO3 but also by a slow addition of NaOCl without tedious pH adjustment.
- Fukuda, Naohiro,Izumi, Minoru,Ikemoto, Tomomi
-
supporting information
p. 3905 - 3908
(2015/06/08)
-
- Scalable and straightforward synthesis of a 2-alkyl-7-arylbenzo-thiophene as a GPR52 agonist via a hemithioindigo derivative
-
A simple and efficient procedure has been developed for the synthesis of the GPR52 agonist N-(2-amino-2-oxoethyl)-3-{4-fluoro-2-[3-(trifluoromethyl)benzyl]-1-benzothien-7-yl}benzamide. The benzo thiophene unit was directly constructed by reduction of a hemithioindigo derivative prepared by an intramolecular Friedel-Crafts cyclization of (phenylsulfanyl)acetic acid, followed by dehydrative benzylidene formation.
- Fukuda, Naohiro,Ikemoto, Tomomi
-
p. 3467 - 3472
(2015/11/17)
-
- Selective Oxidation of Benzyl Alcohols to Aldehydes with a Salophen Copper(II) Complex and tert-Butyl Hydroperoxide at Room Temperature
-
(Figure Presented) An efficient and selective oxidation of benzyl alcohols has been developed using a salophen copper(II) complex as the catalyst and tert-butyl hydroperoxide (TBHP) as the oxidant in the presence of base. Moderate to excellent yields of the corresponding benzaldehydes were obtained at room temperature without the carboxylic acids being formed.
- Chen, Tingting,Cai, Chun
-
supporting information
p. 1334 - 1341
(2015/05/27)
-
- Semi-catalytic reduction of secondary amides to imines and aldehydes
-
Secondary amides can be reduced by silane HSiMe2Ph into imines and aldehydes by a two-stage process involving prior conversion of amides into iminoyl chlorides followed by catalytic reduction mediated by the ruthenium complex [Cp(i-Pr3P)Ru(NCCH3)2]PF6 (1). Alkyl and aryl amides bearing halogen, ketone, and ester groups were converted with moderate to good yields under mild reaction conditions to the corresponding imines and aldehydes. This procedure does not work for substrates bearing the nitro-group and fails for heteroaromatic amides. In the case of cyano substituted amides, the cyano group is reduced to imine.
- Lee, Sun-Hwa,Nikonov, Georgii I.
-
p. 8888 - 8893
(2014/06/09)
-
- METHOD FOR THE CATALYTIC REDUCTION OF ACID CHLORIDES AND IMIDOYL CHLORIDES
-
The present application relates to methods for the catalytic reduction of acid chlorides and/or imidoyl chlorides. The methods comprise reacting the acid chloride or imidoyl chloride with a silane reducing agent in the presence of a catalyst such as [Cp(Pri3P)Ru(NCMe)2]+[PF6]?.
- -
-
Paragraph 0176; 0192; 0193
(2014/08/19)
-
- Diphosphino-functionalised MCM-41-supported palladium complex: An efficient and recyclable catalyst for the formylation of aryl halides
-
The heterogeneous formylation of aryl halides with HCO2Na at atmospheric pressure by carbon monoxide was readily achieved in the presence of the diphosphino-functionalised MCM-41-supported palladium complex in DMF to afford the corresponding aromatic aldehydes in good to excellent yields. This heterogeneous palladium catalyst can be recovered by simple filtration and reused 10 times without any loss of activity.
- Jiang, Jianwen,Wang, Pingping,Cai, Mingzhong
-
p. 218 - 222
(2014/05/06)
-
- A phosphine-free heterogeneous formylation of aryl halides catalyzed by a thioether-functionalized MCM-41-immobilized palladium complex
-
Thioether-functionalized MCM-41-immobilized palladium(II) complex [MCM-41-S-PdCl2] was found to be a highly efficient catalyst for the formylation of aryl iodides or bromides with CO (1 atm) using HCO2Na as a hydrogen source. This phosphine-free heterogeneous palladium complex can be easily recovered by simple filtration and reused for at least 10 consecutive trials without any decreases in activity.
- Hao, Wenyan,Ding, Guodong,Cai, Mingzhong
-
-
- Mechanism of trifluoromethylation of aryl halides with CuCF3and the ortho effect
-
A combined experimental (radical clock, kinetic, Hammett) and computational (DFT, MM) study of the trifluoromethylation reaction of aryl halides with CuCF3 reveals a nonradical mechanism involving Ar-X oxidative addition to the Cu(I) center as the rate determining step. The reaction is second order, first order in each reactant with ΔG? ≈ 24 kcal/mol for PhI (computed ΔG? = 21.9 kcal/ mol). An abrupt change in the gradient on the Hammett plot of log(kR/ kH) versus σp for 11 p-RC6H4I substrates produces two correlations (ρ = +0.69 and +1.83), which is temptingly suggestive of two different reaction pathways. Only one mechanism is operational, however, as advocated by a single linear correlation with σp- (ρ = +0.91), analysis of the experimental ρ values, close similarity of the transition states varying in R and displaying clear signs of -M interactions, and excellent reproduction of the plot by DFT. The long-known yet previously uncomprehended ortho effect has been quantified, for the first time, using the reaction of CuCF3 with a series of o-RC6H4Br: R(kR/kH) = H (1) 2Me (850) 2 (4300) 2H (150 000). With minor contributions from electronic factors, the ortho effect is largely determined by (i) the stabilizing coordination of the o-substituent to Cu in the transition state with the Cu?O distance varying directly with the barrier and (ii) the steric bulk of the o-substituent that raises the ground state free energy of the haloarene (Go ortho - Go H or Go ortho - Go para) by inflicting molecular strain and consequently weakening the Ar-X bond.
- Konovalov, Andrey I.,Lishchynskyi, Anton,Grushin, Vladimir V.
-
supporting information
p. 13410 - 13425
(2015/03/30)
-
- Trifluoromethylation of aryl and heteroaryl halides with fluoroform-derived CuCF3: Scope, limitations, and mechanistic features
-
Fluoroform-derived CuCF3 recently discovered in our group exhibits remarkably high reactivity toward aryl and heteroaryl halides, performing best in the absence of extra ligands. A broad variety of iodoarenes undergo smooth trifluoromethylation with the ligandless CuCF3 at 23-50 C to give the corresponding benzotrifluorides in nearly quantitative yield. A number of much less reactive aromatic bromides also have been trifluoromethylated, including pyridine, pyrimidine, pyrazine, and thiazole derivatives as well as aryl bromides bearing electron-withdrawing groups and/or ortho substituents. Only the most electrophilic chloroarenes can be trifluoromethylated, e.g., 2-chloronicotinic acid. Exceptionally high chemoselectivity of the reactions (no side-formation of arenes, biaryls, and C2F5 derivatives) has allowed for the isolation of a large number of trifluoromethylated products in high yield on a gram scale (up to 20 mmol). The CuCF3 reagent is destabilized by CuX coproduced in the reaction, the magnitude of the effect paralleling the Lewis acidity of CuX: CuCl > CuBr > CuI. While SNAr and SRN1 mechanisms are not operational, there is a well-pronounced ortho effect, i.e., the enhanced reactivity of ortho-substituted aryl halides 2-RC6H4X toward CuCF3. Intriguingly, this ortho-effect is observed for R = NO2, COOH, CHO, COOEt, COCH3, OCH3, and even CH3, but not for R = CN. The fluoroform-derived CuCF3 reagent and its reactions with haloarenes provide an unmatched combination of reactivity, selectivity, and low cost.
- Lishchynskyi, Anton,Novikov, Maxim A.,Martin, Eddy,Escudero-Adan, Eduardo C.,Novak, Petr,Grushin, Vladimir V.
-
p. 11126 - 11146
(2013/12/04)
-
- In situ generation of active species "nO" for the aerobic oxidative deprotection of aldoximes catalyzed by FeCl3/TEMPO
-
A simple and efficient aerobic oxidative deoximation system, using molecular oxygen as the green oxidant and FeCl3/TEMPO as the catalyst, is developed for a wide range of aldoximes. Notably, nitric oxide (NO), an active species for aerobic oxidation reactions, is assumed to be generated in situ from the cleavage of oximes and further confirmed by the existence of a large quantity of NO3- by Ionic Chromatography (IC).
- Zhang, Guofu,Wen, Xin,Wang, Yong,Han, Xingwang,Luan, Yuxin,Zheng, Lebin,Ding, Chengrong,Cao, Xiaoji
-
p. 22918 - 22921
(2013/11/19)
-
- Biooxidation of Primary Alcohols to Aldehydes through Hydrogen Transfer Employing Janibacter terrae
-
Chemoselective oxidations still represent a challenge for chemists. Lyophilized cells of Janibacter terrae were employed for the chemoselective oxidation of primary alcohols to the corresponding aldehydes by hydrogen transfer with the use of acetaldehyde as the hydrogen acceptor. Secondary alcohol moieties were transformed at a much slower rate. The substrate spectrum encompasses substituted benzyl alcohols, whereby substrates with a substituent in the meta position were well tolerated, whereas only very small substituants were tolerated in the ortho position. Furthermore, nalkanols and allylic alcohols were transformed with good conversions. The biocatalyst was compatible with DMSO as a water miscible organic solvent up to 30 % v/v.
- Orbegozo, Thomas,De Vries, Johannes G.,Kroutil, Wolfgang
-
experimental part
p. 3445 - 3448
(2010/09/05)
-
- Efficient and selective oxidation of benzylic alcohol by O2 into corresponding aldehydes on a TiO2 photocatalyst under visible light irradiation: Effect of phenyl-ring substitution on the photocatalytic activity
-
The highly efficient and selective photocatalytic oxidation of benzyl alcohol and its derivatives substituted with-OCH3,-CH 3,-C(CH3)3,-Cl,-CF3 and-NO 2 into corresponding aldehydes has been successfully carried out on TiO2 in the presence of O2 under visible light irradiation. The photocatalytic activity for the formation of the aldehyde was evaluated by a pseudo-first-order reaction, and it was found that the activity is enhanced by phenyl-ring substitution with the electron-releasing groups (-OCH3,-CH3,-C(CH3)3) and the electron-withdrawing groups (-Cl,-CF3 and-NO2). The effects of the substituents and their orientation on the photocatalytic performance of selective oxidation reaction are discussed here. It was shown that the photocatalytic activities are influenced not only by the oxidative potentials of the reactants but also by the stability of the resonant structures of the benzylic alcohol radicals formed by oxidation with a hole, leading to further reactions to form corresponding aldehydes.
- Higashimoto, Shinya,Suetsugu, Nobuaki,Azuma, Masashi,Ohue, Hiroyoshi,Sakata, Yoshihisa
-
experimental part
p. 76 - 83
(2010/11/17)
-
- An unusual reaction of benzalaminoacetals in trifluoroacetic acid: Facile synthesis of 2-benzylpyrazines
-
(Chemical Equation Presented) Benzalaminoacetals (1), upon refluxing with trifluoroacetic acid, lead to 2-benzylpyrazines, rather than the expected isoquinolines. This unusual reaction represents another useful way to prepare a variety of 2-benzylpyrazines from the corresponding benzaldehydes.
- Augustine, John Kallikat,Naik, Yanjerappa Arthoba,Mandal, Ashis Baran,Kundapur, Umesha
-
p. 1176 - 1179
(2008/09/18)
-
- A practical non-cryogenic process for the selective functionalization of bromoaryls
-
A selective and practical bromine-metal exchange process under non-cryogenic conditions was developed by a simple modification of an existing protocol. By directly adding an alkyl lithium RLi reagent to a solution of a bromoaryl substrate ArBr and an alkylmagnesium reagent RMgX, a lithium triarylmagnesiate Ar3MgLi complex formed that allowed for various types of functionalization and more elaborate cross-coupling reactions. The simplicity and improved safety of the method represent a significant improvement over current state of the art that uses lithium trialkylmagnesiate R3MgLi complexes, and is especially advantageous for large-scale synthesis.
- Gallou, Fabrice,Haenggi, Ruedi,Hirt, Hans,Marterer, Wolfgang,Schaefer, Frank,Seeger-Weibel, Manuela
-
p. 5024 - 5027
(2008/12/21)
-
- Correlation analysis of reactivity in the oxidation of substituted benzyl alcohols by morpholinium chlorochromate
-
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
-
scheme or table
p. 669 - 676
(2009/02/08)
-
- Correlation analysis of reactivity in the oxidation of substituted benzyl alcohols by 2,2′-bipyridinium chlorochromate
-
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.
-
body text
p. 496 - 501
(2009/07/18)
-
- Activated iodosylbenzene monomer as an ozone equivalent: Oxidative cleavage of carbon-carbon double bonds in the presence of water
-
Reported here for the first time are the developments of an efficient method for oxidative cleavage of carbon-carbon double bonds yielding carbonyl compounds by using aryl-λ3-iodanes, which involve a combination of iodosylbenzene and HBF4 in the presence of water. The method serves as a safety alternative to ozonolysis. The oxidative cleavage of olefins probably involves the hitherto unknown direct vicinal dihydroxylations of double bonds with aryl-λ3-iodanes and the subsequent oxidative glycol fissions. Cyclic (cyclopentenes, cyclohexenes, etc.) and acyclic olefins are cleaved smoothly under our conditions. In the reaction of electron-deficient styrenes such as m-nitrostyrene, intermediate formation of the corresponding epoxide was detected. A variety of aryloxiranes also undergo an oxidative cleavage of the epoxide rings under our conditions, and aromatic aldehydes were obtained in good yields. Copyright
- Miyamoto, Kazunori,Tada, Norihiro,Ochiai, Masahito
-
p. 2772 - 2773
(2007/10/03)
-
- Effect of structure in benzaldehyde oximes on the formation of aldehydes and nitriles under photoinduced electron-transfer conditions
-
(Chemical Equation Presented) The mechanistic aspects of the photosensitized reactions of a series of benzaldehyde oximes (1a-o) were studied by steady-state (product studies) and laser flash photolysis methods. Nanosecond laser flash photolysis studies have shown that the reaction of the oxime with triplet chloranil (3CA) proceeds via an electron-transfer mechanism provided the free energy for electron transfer (ΔGET) is favorable; typically, the oxidation potential of the oxime should be below 2.0 V. Substituted benzaldehyde oximes with oxidation potentials greater than 2.0 V quench 3CA at rates that are independent of the substituent and the oxidation potential. The most likely mechanism under these conditions is a hydrogen atom transfer mechanism as this reaction should be dependent on the O-H bond strength only, which is virtually the same for all oximes. Product studies have shown that aldoximes feact to give both the corresponding aldehyde and the nitrile. The important intermediate in the aldehyde pathway is the iminoxyl radical, which is formed via an electron transfer-proton transfer (ET-PT) sequence (for oximes with low oxidation potentials) or via a hydrogen atom transfer (HAT) pathway (for oximes with larger oxidation potentials). The nitriles are proposed to result from intermediate iminoyl radicals, which can be formed via direct hydrogen atom abstraction or via an electron-transfer-proton- transfer sequence. The experimental data seems to support the direct hydrogen atom abstraction as evidenced by the break in linearity in the plot of the quenching rates against the oxidation potential, which suggests a change in mechanism. The nitrile product is favored when electron-accepting substituents are present on the benzene ring of the benzaldehyde oximes or when the hydroxyl hydrogen atom is unavailable for abstraction. The latter is the case in pyridine-2-carboxaldoxime (2), where a strong intramolecular hydrogen bond is formed. Other molecules that form weaker intramolecular hydrogen bonds such as 2-furaldehyde oxime (3) and thiophene-2-carboxaldoxime (4) tend to yield increasing amounts of aldehyde.
- De Lijser, H.J. Peter,Hsu, Susan,Marquez, Bernadette V.,Park, Adriana,Sanguantrakun, Nawaporn,Sawyer, Jody R.
-
p. 7785 - 7792
(2007/10/03)
-
- Organic reactions in water: An efficient one-pot synthesis of acyloxiranes from Baylis-Hillman adducts using hypervalent iodine
-
Treatment of Baylis-Hillman adducts with iodosobenzene (PhIO) in the presence of a catalytic amount of KBr in water at room temperature afforded the corresponding acyloxiranes in good yields.
- Das, Biswanath,Holla, Harish,Venkateswarlu, Katta,Majhi, Anjoy
-
p. 8895 - 8897
(2007/10/03)
-
- Catalytic reduction of benzonitrile derivatives to benzoaldehyde derivatives
-
Preparation of benzaldehyde derivatives (I) comprises reacting the corresponding benzonitrile compound (IV) with hydrogen in the presence of (a) water, (b) acid or acid salt with a pKa value of 1-6 in an aqueous reference system and (c) a catalyst containing nickel and aluminum. Preparation of benzaldehyde derivatives of formula (I) comprises reacting the corresponding benzonitrile compound of formula (IV) with hydrogen in the presence of (a) water, (b) acid or acid salt with a pKa value of 1-6 in an aqueous reference system and (c) a catalyst containing nickel and aluminum. [Image] R1>, R2>, R4>, R5>H, F, optionally protected formyl, 1-12C alkyl, 1-12C haloalkyl, 1-12C alkoxy, 1-12C haloalkoxy, 4-14C aryl, 5-15C arylalkyl, PO-[(1-8 C)-alkyl]2, PO-[(4-14C)-aryl]2, PO-[(1-8C)-alkyl)(4-14C)-aryl)], tri(1-8C alkyl)siloxyl, A-CO-B', A-E, A-SO2-B', A-SO2R6>, A-SO3W or A-COW; A : absent or 1-8C alkylene; B' : R6>, OR6>, NHR7> or N(R7>)2; R6>1-8C alkyl, 1-8C haloalkyl, 5-15C arylalkyl or 4-14C aryl; R7>1-8C alkyl, 5-15C arylalkyl or 5-14C aryl, or N(R7>)2cyclic amino; W : OH or NH2, and R3>H, F, Cl or Br. NB: E is not defined.
- -
-
Page/Page column 6
(2008/06/13)
-
- Correlation analysis of reactivity in the oxidation of substituted benzyl alcohols by quinolinium bromochromate
-
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.
-
p. 467 - 473
(2007/10/03)
-
- Kinetics and mechanism of the oxidation of substituted benzyl alcohols by [bis(trifluoroacetoxy)iodo]benzene
-
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.
-
p. 581 - 584
(2007/10/03)
-
- Substituted 3-aryl-5-aryl-[1,2,4]-oxadiazoles and analogs as activators of caspases and inducers of apoptosis and the use thereof
-
The present invention is directed to substituted 3-aryl-5-aryl-[1,2,4]-oxadiazoles and analogs thereof, represented by the Formula I: wherein Ar1, Ar3, A, B and D are defined herein. The present invention also relates to the discovery that compounds having Formula I are activators of caspases and inducers of apoptosis. Therefore, the activators of caspases and inducers of apoptosis of this invention may be used to induce cell death in a variety of clinical conditions in which uncontrolled growth and spread of abnormal cells occurs.
- -
-
-
- Involvement of adsorption effects in the TiO2-sensitized photooxidation rate of benzylic derivatives in CH3CN
-
Competitive kinetic experiments in the TiO2-sensitized photooxidation of some series of differently ring-substituted benzylic derivatives (ArCHROR′) in aerated and/or deaerated CH3CN and in the presence of Ag2SO4 were carried out. From logkrel vs Ep plots it was hypothesized that a changeover of the electron abstraction site occurs on going from electron-donating to electron-withdrawing groups on the ring, from the aromatic moiety to the OCH3 group of benzyl methyl ethers, probably owing to the preferential adsorption of this group on TiO2 with respect to the aromatic ring. This phenomenon is not observed with benzyltrimethylsilanes because the orbital resulting from the overlap between the C-Si bond and the aromatic π system is the only adsorption site. The steric hindrance of an α-methyl group (in benzylic alcohols) or a tert-butyl group (in benzyl tert-butyl ethers) reduces the degree of adsorption but does not influence the shape of the plot because OR′ should still be the preferential adsorption group. This also provides useful information about the surface structure of TiO2 suspended in CH3CN. Copyright
- Del Giacco, Tiziana,Rol, Cesare,Sebastiani, Giovanni V.
-
p. 127 - 132
(2007/10/03)
-
- Substituted N'-(arylcarbonyl)-benzhydrazides, N'-(arylcarbonyl)-benzylidene-hydrazides and analogs as activators of caspases and inducers of apoptosis and the use thereof
-
The present invention is directed to substituted N′-(arylcarbonyl)-benzhydrazides, N′-(arylcarbonyl)-benzylidene-hydrazides and analogs thereof, represented by the Formulae I and II: wherein Ar1, Ar2, and R1-R2 are defined herein. The present invention also relates to the discovery that compounds having Formulae I and II are activators of caspases and inducers of apoptosis. Therefore, the activators of caspases and inducers of apoptosis of this invention may be used to induce cell death in a variety of clinical conditions in which uncontrolled growth and spread of abnormal cells occurs.
- -
-
-
- Synthesis of substituted imidazoles
-
The present invention prepares imidazoles by the selective closure of a keto-amide to form the imidazolyl ring. In particular, the present invention selectively closes a keto-amide substituted with three rings to form a tri-substituted imidazole.
- -
-
-
- Catalytic Conversions in Water. Part 22: Electronic Effects in the (Diimine)palladium(II)-Catalysed Aerobic Oxidation of Alcohols
-
The electronic effects in the (diimine)Pd-(II)-catalysed aerobic oxidation of alcohols were investigated from the viewpoint of both the catalyst and the alcohol. A 'push-pull' mechanism is operative, where both electron-donating substituents on the benzyl alcohol (ρ = -0.58) and electron-withdrawing groups on the 4,4′-disubstituted-2,2′-bipyridine ligand (ρ = +0.18) increase the reaction rate. The results indicate partial reduction of the palladium centre in the transition state of the rate-limiting step.
- Ten Brink, Gerd-Jan,Arends, Isabel W. C. E.,Hoogenraad, Marcel,Verspui, Goeran,Sheldon, Roger A.
-
p. 497 - 505
(2007/10/03)
-
- Correlation analysis of reactivity in the oxidation of substituted benzyl alcohols by quinolinium fluorochromate
-
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.
-
p. 493 - 499
(2007/10/03)
-
- Correlation analysis of reactivity in oxidation of substituted benzyl alcohols by tetrabutylammonium tribromide
-
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.
-
p. 721 - 727
(2007/10/03)
-
- Heterogeneous permanganate oxidation of styrene and cinnamic acid derivatives: A simple and effective method for the preparation of benzaldehydes
-
Styrene and cinnamic acid derivatives yield correspondingly substituted benzaldehydes when oxidized by permanganate under heterogeneous conditions. Reaction of terminal aliphatic alkenes under similar conditions gives discouragingly low yields; however, ketones and ketols are obtained in very good yields from the oxidation of 2,2-disubstituted and trisubstituted alkenes, respectively. Alumina and Amberlite IR-120 can be used as solid supports in these reactions with equally good results.
- Lai,Lee
-
p. 1645 - 1648
(2007/10/03)
-
- Synthesis of primary aromatic amides by aminocarbonylation of aryl halides using formamide as an ammonia synthon
-
Primary aromatic amides were prepared by a palladium-catalyzed aminocarbonylation reaction of aryl halides in high yields (70-90%) using formamide as the amine source. The reactions require a palladium catalyst in combination with a nucleophilic Lewis base such as imidazole or 4-(dimethylamino)pyridine (DMAP). Aryl, heteroaryl, and vinyl bromides and chlorides were converted to the primary amides under mild conditions (5 bar, 120 °C) using 1 mol % of a palladium-phosphine complex. Best results were obtained in dioxane using triphenylphosphine as the ligand and DMAP as the base. For activated aryl bromides, a phosphine-to-palladium ratio of 2:1 was sufficient, but less reactive aryl bromides or aryl chlorides required ligand-to-palladium ratios up to 8:1 in order to stabilize the catalyst and achieve full conversion. The influence of catalyst, base, solvent, pressure, and temperature was studied in detail. The mechanism of the. reaction could be clarified by isolating and identifying the reaction intermediates. In addition, methylamides and dimethylamides were prepared by the same method using N-methylformamide and N,N-dimethylformamide as the amine source.
- Schnyder,Beller,Mehltretter,Nsenda,Studer,Indolese
-
p. 4311 - 4315
(2007/10/03)
-