- Decarboxylative Ritter-Type Amination by Cooperative Iodine (I/III)─Boron Lewis Acid Catalysis
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Recent years have witnessed important progress in synthetic strategies exploiting the reactivity of carbocations via photochemical or electrochemical methods. Yet, most of the developed methods are limited in their scope to certain stabilized positions in molecules. Herein, we report a metal-free system based on the iodine (I/III) catalytic manifold, which gives access to carbenium ion intermediates also on electronically disfavored benzylic positions. The unusually high reactivity of the system stems from a complexation of iodine (III) intermediates with BF3. The synthetic utility of our decarboxylative Ritter-type amination protocol has been demonstrated by the functionalization of benzylic as well as aliphatic carboxylic acids, including late-stage modification of different pharmaceutical molecules. Notably, the amination of ketoprofen was performed on a gram scale. Detailed mechanistic investigations by kinetic analysis and control experiments suggest two mechanistic pathways.
- Narobe, Rok,Murugesan, Kathiravan,Schmid, Simon,K?nig, Burkhard
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p. 809 - 817
(2022/01/15)
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- Hydrosilylative reduction of primary amides to primary amines catalyzed by a terminal [Ni-OH] complex
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A terminal [Ni-OH] complex1, supported by triflamide-functionalized NHC ligands, catalyzes the hydrosilylative reduction of a range of primary amides into primary amines in good to excellent yields under base-free conditions with key functional group tolerance. Catalyst1is also effective for the reduction of a variety of tertiary and secondary amides. In contrast to literature reports, the reactivity of1towards amide reduction follows an inverse trend,i.e., 1° amide > 3° amide > 2° amide. The reaction does not follow a usual dehydration pathway.
- Bera, Jitendra K.,Pandey, Pragati
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supporting information
p. 9204 - 9207
(2021/09/20)
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- Acetonitrile and benzonitrile as versatile amino sources in copper-catalyzed mild electrochemical C-H amidation reactions
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A mild, efficient electrochemical approach to the site-selective direct C-H amidation of benzene and its derivatives with acetonitrile and benzonitrile has been developed. It has been shown that joint electrochemical oxidation of various arenes in the presence of a copper salt as a catalyst and nitriles leads to the formation of N-phenylacetamide from benzene and N-benzylacetamides from benzyl derivatives (up to 78% yield). A favorable feature of the process is mild conditions (room temperature, ambient pressure, no strong oxidants) that meet the criteria of green chemistry.
- Budnikova, Yulia,Kononov, Alexander,Rizvanov, Ildar,Strekalova, Sofia
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p. 37540 - 37543
(2021/12/07)
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- Synthesis of task-specific imidazolium ionic liquid as an efficient catalyst in acetylation of alcohols, phenols, and amines
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Herein, we report the synthesis of task-specific amino-functionalized imidazolium ionic liquid, acetate1-(2-tert-butoxycarbonylamino-ethyl)-3-methyl-3H-imidazol-1-ium; (Boc-NH-EMIM.OAc), as an efficient catalyst for the acetylation of alcohols, phenols, and amines in the presence of acetic anhydride (acetylating reagent). Remarkably, acetic anhydride in the presence of 10?molpercent of catalyst (Boc-NH-EMIM.OAc) under solvent-free conditions showed excellent acetylation activity in shorter duration of time. On the basis of this, a general procedure for acetylation of alcohols, phenols, and amines has been developed. The ionic liquid (Boc-NH-EMIM.OAc) can be readily recovered and reused successfully up to four consecutive cycles without any significant loss of its catalytic activity. We have been able to show that this acetylating method has many advantages. It gives high yields, takes shorter time, and develops the possibility of benign environmental-friendly process.
- Chaubey, Snehkrishn A.,Mishra, Roli
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p. 3259 - 3268
(2020/04/17)
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- Environmentally benign decarboxylative: N-, O-, and S-Acetylations and acylations
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An operationally simple and general method for acetylation and acylation of a wide variety of substrates (amines, alcohols, phenols, thiols, and hydrazones) has been reported. Meldrum's acid and its derivatives have been used as an air-stable, non-volatile, cost-effective, and easy to handle acetylating/acylating agent. Easily separable byproducts (CO2 and acetone) allowed the isolation of analytically pure acetylated products without the requirement of work-up and any chromatography. This journal is
- Ghosh, Santanu,Purkait, Anisha,Jana, Chandan K.
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supporting information
p. 8721 - 8727
(2020/12/30)
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- Reductive Amidation without an External Hydrogen Source Using Rhodium on Carbon Matrix as a Catalyst
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An efficient method for preparation of secondary amides from primary amides and aldehydes using rhodium on carbon matrix as catalyst was developed. The method does not require any external hydrogen source and carbon monoxide is used as a reducing agent. The most active rhodium catalysts were characterized by BET, TEM and XPS techniques. Unexpectedly, it was found that heterogeneous rhodium on carbon matrix works as precatalyst for homogenous active species due to leaching of rhodium to the solution. Various secondary amides were synthesized and checked for antifungal activity. 4-Methoxy-N-(4-methoxybenzyl)benzamide demonstrated promising activity against Rhizoctonia Solani.
- Tsygankov, Alexey A.,Makarova, Maria,Afanasyev, Oleg I.,Kashin, Alexey S.,Naumkin, Alexander V.,Loginov, Dmitry A.,Chusov, Denis
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p. 112 - 117
(2019/11/28)
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- Fe3O4@PEG core/shell nanoparticles as magnetic nanocatalyst for acetylation of amines and alcohols using ultrasound irradiations under solvent-free conditions
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Abstract: Ultrasound irradiation was used to prepare one-pot Fe3O4@PEG core/shell nanostructure for the first time. The morphology, structure, and physicochemical properties were specified by different analytical techniques including field emission scanning electron microscopy, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray powder diffraction, and vibrating sample magnetometer. For acetylation of phenols, alcohols, and amines, the synthesized Fe3O4@PEG core/shell nanoparticles were used as an efficient heterogeneous and green catalyst with acetic anhydride under sonication applying mild reaction conditions. Different electron-withdrawing and electron-donating substrates indicate a prominent yield of desired products with the merit of reusability of Fe3O4@PEG nanocatalyst and magnetic separation. Graphical Abstract: [Figure not available: see fulltext.].
- Veisi, Hojat,Nikseresht, Ahmad,Rostami, Afsaneh,Hemmati, Saba
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p. 507 - 520
(2018/10/24)
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- Preparation of Polydopamine Sulfamic Acid-Functionalized Silica Gel as Heterogeneous and Recyclable Nanocatalyst for Acetylation of Alcohols and Amines Under Solvent-Free Conditions
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To fabricate SiO2/PDA–SO3H nanocatalyst, a suitable method is designed for the loading of sulfonic acid groups on the surface of polydopamine (PDA)-encapsulated SiO2 nanoparticles. To bridge the gap between heterogeneous and homogeneous catalysis, surface functionalization of silica gel is an elegant procedure. The morphology, structure, and physicochemical features were specified using different analytical techniques including field emission scanning electron microscopy (FESEM), Fourier transformed infrared spectroscopy (FT-IR), high resolution-transmission electron microscopy (HR-TEM), energy dispersive X-ray spectroscopy (EDS), wavelength-dispersive X-ray spectroscopy (WDX), X-ray photoelectron spectroscopy (XPS), and back titration. The SiO2/PDA–SO3H nanoparticles are efficient nanocatalysts for the acetylation of many alcohols, phenols, and amines with acetic anhydride under solvent-free conditions in good to excellent yields. Moreover, the reuse and recovery of the catalyst was shown seven times without detectible loss in activity. Graphical Abstract: [Figure not available: see fulltext.]
- Veisi, Hojat,Vafajoo, Saba,Bahrami, Kiumars,Mozafari, Bita
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p. 2734 - 2745
(2018/07/30)
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- Ruthenium-Catalyzed Reductive Amidation without an External Hydrogen Source
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A catalytic reaction between aldehydes and primary amides that leads to N-alkylated amides was investigated. The developed protocol employs carbon monoxide as a deoxygenative agent and, therefore, avoids the use of an external hydrogen source. Cyclopentad
- Yagafarov, Niyaz Z.,Muratov, Karim M.,Biriukov, Klim,Usanov, Dmitry L.,Chusova, Olga,Perekalin, Dmitry S.,Chusov, Denis
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supporting information
p. 557 - 563
(2018/02/09)
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- Transition-Metal- and Halogen-Free Oxidation of Benzylic sp 3 C-H Bonds to Carbonyl Groups Using Potassium Persulfate
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Aryl carbonyl compounds including acetophenones, benzophenones, imides, and benzoic acids are prepared from benzyl substrates using potassium persulfate as oxidant with catalytic pyridine in acetonitrile under mild conditions. Neither transition metals nor halogens are involved in the reactions.
- Hu, Yixin,Zhou, Lihong,Lu, Wenjun
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supporting information
p. 4007 - 4016
(2017/08/29)
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- Mechanochemical N-alkylation of imides
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The mechanochemical N-alkylation of imide derivatives was studied. Reactions under solvent-free conditions in a ball mill gave good yields and could be put in place of the classical solution conditions. The method is general and can be applied to various imides and alkyl halides. Phthalimides prepared under ball milling conditions were used in a mechanochemical Gabriel synthesis of amines by their reaction with 1,2-diaminoethane.
- Bri?, Anamarija,Dud, Mateja,Margeti?, Davor
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supporting information
p. 1745 - 1752
(2017/09/27)
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- Direct Synthesis of Amides by Dehydrogenative Coupling of Amines with either Alcohols or Esters: Manganese Pincer Complex as Catalyst
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The first example of base-metal-catalysed synthesis of amides from the coupling of primary amines with either alcohols or esters is reported. The reactions are catalysed by a new manganese pincer complex and generate hydrogen gas as the sole byproduct, thus making the overall process atom-economical and sustainable.
- Kumar, Amit,Espinosa-Jalapa, Noel Angel,Leitus, Gregory,Diskin-Posner, Yael,Avram, Liat,Milstein, David
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supporting information
p. 14992 - 14996
(2017/10/25)
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- Acetic acid as a catalyst for the N-acylation of amines using esters as the acyl source
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We report a cheap and simple method for the acetylation of a variety of amines using catalytic acetic acid and either ethyl acetate or butyl acetate as the acyl source. Catalyst loadings as low as 10 mol% afforded acetamide products in excellent yields at temperatures ranging from 80-120 °C. The methodology can also be successfully applied for the synthesis of a broad range of other amides, including the formation of formamides at 20 °C.
- Sanz Sharley, Daniel D.,Williams, Jonathan M. J.
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supporting information
p. 2020 - 2023
(2017/02/15)
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- Dichotomy of Atom-Economical Hydrogen-Free Reductive Amidation vs Exhaustive Reductive Amination
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Rh-catalyzed one-step reductive amidation of aldehydes has been developed. The protocol does not require an external hydrogen source and employs carbon monoxide as a deoxygenative agent. The direction of the reaction can be altered simply by changing the solvent: reaction in THF leads to amides, whereas methanol favors formation of tertiary amines.
- Kolesnikov, Pavel N.,Usanov, Dmitry L.,Muratov, Karim M.,Chusov, Denis
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supporting information
p. 5657 - 5660
(2017/10/25)
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- Photosensitized oxidation of aryl benzyl sulfoxides. Evidence for nucleophilic assistance to the c-s bond cleavage of aryl benzyl sulfoxide radical cations
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The radical cations of a series of aryl benzyl sulfoxides (4-X-C6H4CH2SOC6H4Y+?) have been generated by photochemical oxidation of the parent sulfoxides sensitized by 3-cyano-N-methylquinolinium perchlorate (3-CN-NMQ+ClO4-). Steady-state photolysis experiments showed the prevailing formation of benzylic products deriving from the C-S fragmentation in the radical cations, together with sulfur-containing products. Formation of sulfoxide radical cations was unequivocally established by laser flash photolysis experiments showing the absorption bands of 3-CN-NMQ? (λmax = 390 nm) and of the radical cations (λmax = 500-620 nm). The decay rate constants of radical cations, determined by LFP experiments, decrease by increasing the electron-donating power of the arylsulfinyl Y substituent and to a smaller extent by increasing the electron-withdrawing power of the benzylic X substituent. A solvent nucleophilic assistance to the C-S bond cleavage has been suggested, supported by the comparison of substituent effects on the same process occurring in aryl tert-butyl sulfoxide radical cations. DFT calculations, performed to determine the bond dissociation free energy in the radical cations, the transition state energies associated with the unimolecular C-S bond cleavage, and the charge and spin delocalized on their structures, were also useful to endorse the nucleophilic assistance to the C-S scission.
- Del Giacco, Tiziana,Lanzalunga, Osvaldo,Lapi, Andrea,Mazzonna, Marco,Mencarelli, Paolo
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p. 2310 - 2318
(2015/09/08)
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- An attractive route to transamidation catalysis: Facile synthesis of new o-aryloxide-N-heterocyclic carbene ruthenium(II) complexes containing trans triphenylphosphine donors
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Well-defined robust ruthenium(II) complexes 3a-d bearing o-aryloxide-N-heterocyclic carbene ligands with different wingtip substituents (3a (R = Me), 3b (R = Ph), 3c (R = iPr) and 3d (R = Mes)) in the imidazole ring were synthesized in good yields by the reaction of imidazolium proligands with metal precursor [RuHCl(CO)(PPh3)3] by transmetallation from the corresponding silver carbene complexes. All the Ru(II)-NHC complexes have been characterized by elemental analyses, spectroscopic methods as well as ESI mass spectrometry. The molecular structure of the complex 3a was identified by means of single-crystal X-ray diffraction analysis, which revealed that the complexes possess a distorted octahedral geometry. In order to explore the catalytic potential of the synthesized complexes, all the four [Ru-NHC] complexes [3a-d] were tested as catalysts for transamidation of carboxamides with amines. Notably, the complex 3a was found to be very efficient and versatile catalyst toward transamidation of a wide range of amides with amines.
- Nirmala, Muthukumaran,Prakash, Govindan,Viswanathamurthi, Periasamy,Malecki, Jan Grzegorz
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- H-β-zeolite catalyzed transamidation of carboxamides, phthalimide, formamides and thioamides with amines under neat conditions
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Efficient transamidation of unactivated carboxamides, phthalimides, formamides and thioamides with amines under solvent-free conditions using H-β-zeolite as a green and recyclable heterogeneous catalyst is described. Easy work up, high purity of the products, recyclability and environmentally-friendly nature of the catalyst are the attractive features of the present methodology. This is the first report for the transamidation of thioamides under heterogeneous conditions.
- Rao, Sadu Nageswara,Chandra Mohan, Darapaneni,Adimurthy, Subbarayappa
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p. 95313 - 95317
(2015/11/24)
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- Magnetic CoFe2O4 nanoparticle immobilized N-propyl diethylenetriamine sulfamic acid as an efficient and recyclable catalyst for the synthesis of amides via the Ritter reaction
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A magnetic CoFe2O4 nanoparticle immobilized diamine-N-sulfamic acid (CoFe2O4@SiO2-DASA) was synthesized and used as efficient heterogeneous catalyst for the synthesis of amides via the Ritter reaction under solvent-free conditions. The magnetic nanocatalyst could be readily recovered by applying an external magnet and recycled several times without considerable loss of its catalytic activity.
- Zhao, Xiao-Na,Hu, Hai-Chuan,Zhang, Fu-Jun,Zhang, Zhan-Hui
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p. 258 - 265
(2014/07/08)
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- Tandem synthesis of amides and secondary amines from esters with primary amines under solvent-free conditions
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An iridium(III)-catalyzed tandem synthesis of amides and amines from esters under solvent-free conditions is described. A commercially available iridium(III) complex, [Cp*IrCl2]2, with sodium acetate showed the best activity for the synthesis of amides and secondary amines. The amide was formed by ester-amide exchange which generates an alcohol in situ which is subsequently transformed to a secondary amine via hydrogen autotransfer. This synthetic protocol with high atom economy generates water as the sole by-product and can afford amides and amines from various esters in a one-pot reaction, expanding the synthetic versatility of ester transformations.
- Lee, Jeongbin,Muthaiah, Senthilkumar,Hong, Soon Hyeok
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p. 2653 - 2660
(2014/09/17)
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- Chitosan: An efficient recyclable catalyst for transamidation of carboxamides with amines under neat conditions
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A novel chitosan-catalyzed transamidation of carboxamides with amines under solvent-free conditions is described. A series of amide derivatives as well as more challenging aryl and alkyl amines with long-chain alkyl substituents could be selectively converted into the corresponding transamidation products, which are frequently found in biologically active compounds and pharmaceuticals. Under similar reaction conditions benzo[d]heterocycles were also obtained via a one-pot synthesis through transamidation and subsequent dehydration. Recyclability of chitosan was demonstrated, with quantitative yields of products obtained without any loss of catalytic activity. the Partner Organisations 2014.
- Nageswara Rao, Sadu,Chandra Mohan, Darapaneni,Adimurthy, Subbarayappa
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supporting information
p. 4122 - 4126
(2014/10/15)
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- L-Proline: An efficient catalyst for transamidation of carboxamides with amines
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In the presence of a catalytic amount of l-proline (10 mol %), transamidations of carboxamides with amines were achieved under solvent-free conditions. The transamidation process is compatible with a wide range of amines.
- Rao, Sadu Nageswara,Mohan, Darapaneni Chandra,Adimurthy, Subbarayappa
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supporting information
p. 1496 - 1499
(2013/06/27)
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- One-pot stibine modified Co2(CO)8 catalyzed reductive N-alkylation of primary amides with carbonyl compounds
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A one-pot stibine modified Co2(CO)8 homogeneous catalytic reductive N-alkylation of primary amides using aldehydes/ketones as alkylating agents, is reported. Good to excellent yields of a wide range of secondary amides are obtained (up to 97%) under relative mild conditions.
- Rubio-Pérez, Laura,Sharma, Pankaj,Pérez-Flores, F. Javier,Velasco, Luis,Arias, J. Luis.,Cabrera, Armando
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experimental part
p. 2342 - 2348
(2012/04/10)
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- Dynamic path bifurcation in the Beckmann reaction: Support from kinetic analyses
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The reactions of oximes to amides, known as the Beckmann rearrangement, may undergo fragmentation to form carbocations + nitriles when the migrating groups have reasonable stability as cations. The reactions of oxime sulfonates of 1-substituted-phenyl-2-propanone derivatives (7-X) and related substrates (8-X, 9a-X) in aqueous CH3CN gave both rearrangement products (amides) and fragmentation products (alcohols), the ratio of which depends on the system; the reactions of 7-X gave amides predominantly, whereas 9a-X yielded alcohols as the major product. The logk-logk plots between the systems gave excellent linear correlations with slopes of near unity. The results support the occurrence of path bifurcation after the rate-determining TS of the Beckmann rearrangement/fragmentation reaction, which has previously been proposed on the basis of molecular dynamics simulations. It was concluded that path-bifurcation phenomenon could be more common than thought and that a reactivity-selectivity argument based on the traditional TS theory may not always be applicable even to a well-known textbook organic reaction.
- Yamamoto, Yutaro,Hasegawa, Hiroto,Yamataka, Hiroshi
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experimental part
p. 4652 - 4660
(2011/07/29)
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- Poly-(N,N′-dibromo-N-ethyl-benzene-1,3-disulfonamide) and N,N,N′,N′- tetrabromobenzene-1,3-disulfonamide as highly efficient catalysts, and (AC2O/SIO2) as a heterogeneous system for the acetylation of alcohols, amines, and thiols under microwave irradiation
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Chemical Equation Presented Poly-(N,N′-dibromo-N-ethyl-benzene-1,3- disulfonamide) (PBBS) and N,N,N′,N′-tetrabromobenzene-1,3- disulfonamide (TBBDA) are good activators and catalytic reagents for the acetylation of alcohols, amines, and thiols. The presented method has the advantages of mild conditions, chemoselectivity, and good to high yields, and uses noncorrosive, inexpensive, recyclable, and environmentally friendly catalysts. We have also demonstrated that combining SiO2 with microwave energy provides an efficient, fast, convenient, and easy workup procedure for the synthesis of mono- and disubstituted acetates, acetamides, and thioacetamides. Copyright Taylor & Francis Group, LLC.
- Veisi, Hojat,Ghorbani-Vaghei, Ramin,Eskandari, Hosna,Hemmati, Saba,Rezaei, Ardashir,Hajinazari, Somaye,Far, Mohammad Raoof Heidari,Entezari, Azam
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experimental part
p. 213 - 219
(2011/04/24)
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- N-Alkylation of carbamates and amides with alcohols catalyzed by a Cp*Ir complex
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New atom-economical catalytic systems consisting of [Cp*IrCl2]2/NaOAc (Cp*=pentamethylcyclopentadienyl) for the N-alkylation of carbamates and amides using alcohols as alkylating agents under solvent-free conditions have been developed. For example, the reaction of n-butyl carbamate with benzyl alcohol in the presence of [Cp*IrCl2]2 (5.0 mol % Ir) and NaOAc (5.0 mol %) at 130 °C under the absence of solvent gives n-butyl N-benzylcarbamate in the yield of 94%. The present catalytic system is applicable to not only carbamates but also amides, and only harmless water is produced as co-product.
- Fujita, Ken-ichi,Komatsubara, Atsuo,Yamaguchi, Ryohei
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experimental part
p. 3624 - 3628
(2009/09/06)
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- Pyrano-[2,3b]-pyridines as potassium channel antagonists
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The design and synthesis of a series of highly functionalized pyrano-[2,3b]-pyridines is described. These compounds were assayed for their ability to block the IKur channel encoded by the gene hKV1.5 in patch-clamped L-929 cells. Six of the compounds in this series showed sub-micromolar activity, the most potent being 4-(4-ethyl-benzenesulfonylamino)-3-hydroxy-2,2-dimethyl-3,4-dihydro-2H-pyrano[2,3b]-pyridine-6-carboxylic acid ethyl-phenyl-amide with an IC50 of 378 nM.
- Finlay, Heather J.,Lloyd, John,Nyman, Michael,Conder, Mary Lee,West, Tonya,Levesque, Paul,Atwal, Karnail
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p. 2714 - 2718
(2008/12/21)
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- Benzyl amide-ketoacid inhibitors of HIV-integrase
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Integrase is one of three enzymes expressed by HIV and represents a validated target for therapy. Previous reports have demonstrated that the diketoacid-based chemotype is a useful starting point for the design of inhibitors of this enzyme. In this study, one of the ketone groups is replaced by a benzylamide resulting in a new potent chemotype. A preliminary SAR study is carried out to investigate the substitution requirements on the phenyl ring and methylene group of the benzylamide.
- Walker, Michael A.,Johnson, Timothy,Naidu, B. Narasimhulu,Banville, Jacques,Remillard, Roger,Plamondon, Serge,Martel, Alain,Li, Chen,Torri, Albert,Samanta, Himadri,Lin, Zeyu,Dicker, Ira,Krystal, Mark,Meanwell, Nicholas A.
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p. 4886 - 4890
(2008/02/13)
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- Perfluorinated sulfonic acid resin (Nafion-H) catalysed Ritter reaction of benzyl alcohols
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Perfluorinated sulfonic acid resin (Nafion-H) catalyst found to be effective in promoting the Ritter reaction of benzyl alcohols with nitriles such as acetonitrile, acrylonitrile and benzonitrile to give the corresponding N-benzylamides.
- Yamato, Takehiko,Hu, Jian-Yong,Shinoda, Naoki
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p. 641 - 643
(2008/09/17)
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- Mechanistic investigations on the reaction between amines or amides and an alkylperoxy-λ3-iodane
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A mechanism involving the intermediate formation of an amine radical cation by single-electron transfer is proposed for the oxidation of secondary amines with alkylperoxy-λ3-iodane. On the other hand, the oxidation of acetamides probably proceeds by a radical process, which involves the direct hydrogen abstraction of the methylene group α to the nitrogen atom.
- Sueda, Takuya,Kajishima, Daisuke,Goto, Satoru
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p. 3307 - 3310
(2007/10/03)
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- Solid-phase intermolecular radical reactions 2: Synthesis of C-glycopeptide mimetics via a novel acrylate acceptor
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A novel tetrafluorophenol-linked acrylate is reported as an activated acceptor for intermolecular radical reactions. Addition of alkyl radicals led to pure products in good yields. We include here the first syntheses of C1- and C6-linked glycosides using
- Caddick, Stephen,Hamza, Daniel,Wadman, Sjoerd N.,Wilden, Jonathan D.
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p. 1775 - 1777
(2007/10/03)
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- 2-Acylpyridazin-3-ones: Novel mild and chemoselective acylating agents for amines
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2-Acyl-4,5-dichloropyridazin-3-ones served as excellent novel N-acylating reagents for amines under neutral conditions in organic solvent. They are convenient, chemoselective and easy to handle stable N-acylating reagents of amines.
- Kang, Young-Jin,Chung, Hyun-A,Kim, Jeum-Jong,Yoon, Yong-Jin
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p. 733 - 738
(2007/10/03)
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- Evidence for intermolecular interaction between sulfonium and sulfide sulfur atoms and its application to synthesis of cyclic bis(disulfide) dimer
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On the basis of the remote Pummerer reaction of p-bis(alkylthio)-aromatic S-oxide, the intermolecular interaction between the sulfonium and sulfide sulfur atoms is described. (1) In marked contrast to the Pummerer reaction of 1b-d3 with (CF3CO)2O (J. Org. Chem. 1999, 64, 3190-3195), the reaction of 3,3′,5,5′-tetramesityl-4-(trideuteriomethylsulfinyl)-4′- (methylthio)biphenyl (1a-d3) as a sterically hindered analogue of 1b gave only 2a-d2. (2) Both reactions of the two unsymmetrical regioisomers of 1-(ethylthio)-4-(methylthio)benzene S-oxide (5a and 5b) with (CF3CO)2O afforded a mixture of the mono-Pummerer products 6a and 6b, the bis-Pummerer product 7, and the bissulfide 8 in a similar ratio. The quenching at the initial stage of both reactions produced 5a, 5b, 8, and the bis-sulfoxide 10 in a similar ratio. These results indicate the equilibrium in the intermolecular interaction between the sulfur atoms. (3) The reaction of the p-bis(benzylthio)aromatic S-oxide 16 with (CF3SO2)2O gave the cyclic bis(disulfide) dimer 17 for the diphenyl sulfide and diphenylmethane spacers or the cyclic tetrakis(disulfide) tetramer 19 for the benzene and biphenyl spacers via the debenzylation of an intermolecular dithia dication. The cyclic bis(dithia dication) dimer A resulting from the intermolecular interaction between the sulfonium and sulfide sulfur atoms is proposed as an intermediate throughout the present reactions.
- Kobayashi,Koyama,Kono,Namatame,Nakamura,Furukawa
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p. 2085 - 2090
(2007/10/03)
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- A Study of Essentially Free Carbocations Derived via Diazonium and Oxo Diazonium Ions in the Liquid Phase
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Nitrogen- and nitrous oxide-separated ion pairs containing 4-substituted benzyl cations and carboxylate or tosylate anions were prepared by thermolysis of N-nitroso- and N-nitroamides, acidification of phenyldiazomethane, and nitrosation of N-benzyl-O-benzoylhydroxylamine. The cations were generated in benzene/toluene and benzene/anisole mixtures and were found to partition between the counterion and the solvent and between the aromatic cosolvent and benzene. A familial relationship among the methods was observed. As the cation became more reactive, the yield of solvent-derived products (SDPs) rose and the ratio of rate constants for its reaction with toluene versus benzene, kT/kB, fell. The yield of SDP also rose as the temperature was decreased and as N2 was replaced by N2O; however, kT/kB remained unchanged. Inert diluents had no effect on kT/kB but decreased hydrocarbon yield by 40% on 2-fold dilution. In the presence of reactive diluents that are converted into secondary alkylating agents, both the % hydrocarbon and kT/kB rose. These results are interpreted in terms of the intermediacy of inert-molecule-separated ion pairs (IMSIPs) in deamination. The cation reacted with benzoates and tosylates not only at the oxygens but also at the ipso carbon; subsequent decarboxylation and desulfonylation, respectively, led to diphenylmethanes. The ester/SDP ratio is introduced as a new measure of carbocation reactivity.
- Darbeau, Ron W.,White, Emu H.,Song, Fenhong,Darbeau, Nyla R.,Chou, James
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p. 5966 - 5978
(2007/10/03)
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- Interconversion and rearrangement of radical cations. Part 2. Photoinduced electron transfer and electrochemical oxidation of 1,4-bis(methylene)cyclohexane
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The photoinduced electron transfer and electrochemical oxidation of 1,4-bis(methylene)cyclohexane (2) in acetonitrile have been studied in the presence and absence of a nucleophile (methanol).The photoinduced electron transfer reactions of 2 in acetonitrile-methanol solution with 1,4-dicyanobenzene (8) as the electron acceptor gives two products: 4-(methoxymethyl)-1-methylenecyclohexane (16) and 4-(4-cyanophenyl)-4-(methoxymethyl)-1-methylenecyclohexane (17).These products arise from nucleophilic attack on the radical cation followed by either reduction and protonation or combination with the radical anion of the electron acceptor, 1,4-dicyanobenzene (8.-).These results are in accord with the proposed mechanism of the photochemical nucleophile-olefin combination, aromatic substitution (photo-NOCAS) reaction.In the absence of a nucleophile, the photoinduced electron transfer reaction of 2 gives rise to several interesting and unexpected products 18-25 which result from complex reaction mechanisms involving radical, ionic and radical ion intermediates.The electrooxidation of 2 in acetonitrile in the presence of methanol leads to products 27-35.Under these conditions the radical cation 2.+ reacts with the nucleophile followed by a second oxidation and subsequent reactions leading to products (electrochemical-chemical-electrochemical, ECE).One of the products (28) is the results of protonation of 2 followed by nucleophilic attack.The electrochemical oxidation of 2 in acetonitrile (no methanol) yields 2.+ which is deprotonated and then further oxidized to give 39-43.These products arise from ionic intermediates (ECE); oxidation of 2 all the way to aromatic compounds was observed in 39-41.In none of these experiments was there any evidence for the formation of cyclized products, nor was there any indication of carbon-carbon bond cleavage in 2.+.The products are consistent with the initial formation of the intermediate radical cation.The products as well as the possible mechanisms of formation of these species are discussed.
- Lijser, H. J. P. de,Arnold, Donald R.
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p. 1369 - 1380
(2007/10/03)
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- Kinetics and mechanism of aminolysis of phenyl acetates and phenyl trimethylacetates in dimethyl suldoxide
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Kinetic studies have been carried out on the reactions of phenyl acetates and phenyl trimethylacetates in dimethyl sulfoxide.The rate ratios between the two acyl compounds, and the positive sign and large magnitude of the cross-interaction constants, ρXZ, between substituents X in the nucleophile and Z in the leaving group are considered to favour the rate-limiting expulsion of aryl oxide from the tetrahedral intermediate T+/-.The aprotic solvent used makes the proposed mechanism with a cyclic transition state more attractive especially in view of the greater charge dispersion and assistance to leaving group departure provided in such a structure.
- Koh, Han Joong,Kim, Seung Il,Lee, Byung Choon,Lee, Ikchoon
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p. 1353 - 1358
(2007/10/03)
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- New Allyl Group Acceptors for Palladium Catalyzed Removal of Allylic Protections and Transacylation of Allyl Carbamates.
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Key words: allylic protecting groups, palladium catalysis, transacylation, phenyltrihydrosilane, N-methyl-N-(trimethylsilyl)trifluoroacetamide.Allyl carboxylates, carbamates and phenoxides may be cleaved or transacylated in the presence of palladium catalyst and either phenyltrihydridosilane or N-methyl-N-(trimethylsilyl)trifluoroacetamide.These reactions are totally compatible with the presence of Boc and, as far as phenyltrihydrosilane is concerned, Fmoc protections.
- Dessolin, Michele,Guillerez, Marie-George,Thieriet, Nathalie,Guibe, Francois,Loffet, Albert
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p. 5741 - 5744
(2007/10/02)
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- Structural Effects in the TiO2-Photocatalyzed Oxidation of Alkylaromatic Compounds in Acetonitrile in the Presence of Ag2SO4
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The TiO2-sensitized photochemical reactions of some alkylbenzenes (ArCH2R; R = H, Me), 1-aryl-2-propanols, and corresponding methyl esters (ArCH2C(OR'')R'CH3; R', R'' = H, Me) have been investigated in MeCN, in the presence of Ag2SO4, which traps the photogenerated electrons.With ArCH2R, the corresponding radical cations are generated by the photoexcited TiO2 and are then deprotonated to from benzyl radicals; from the latter 1,2-diarylethanes, 3-arylpropanonitriles, and benzylacetamides are obtained as major products.With ArCH2C(OR'')R'CH3, the formed radical cations undergo C-C bond cleavage as the only observed route, when Ar = Ph.However, when Ar = 4-MeOPh and R' = H, the radical cation undergoes C-H bond cleavage as the major or exclusive reaction path.These results are compared with those obtained in the corresponding homogeneous photochemical reactions, and their implications with respect to the role of the structure on the side-chain reactivity of aromatic radical cations are discussed.
- Baciocchi, Enrico,Rol, Cesare,Sebastiani, Giovanni V.,Taglieri, Luca
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p. 5272 - 5276
(2007/10/02)
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- Highly selective amidation of benzylic alcohols with nitriles. A modified ritter reaction
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Benzyl alcohols react selectively with different nitriles in the presence of a catalytic amount of boron trifluoride and produce amides in high yields. Deactivated p-nitrobenzyl, allylic, primary, secondary, and tertiary saturated alcohols do not react.
- Firouzabadi,Sardarian,Badparva
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p. 601 - 607
(2007/10/02)
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- Simple, high yield preparation of N-benzylacetamides by Lewis acid-catalysed reaction of benzyl chlorides or benzyl methyl ethers with acetonitrile
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Reaction of either benzyl chlorides or benzyl methyl ethers with hydrated ferric chloride in acetonitrile results in smooth Ritter reaction and formation of N-benzylacetamides in excellent yield.
- Kacan,McKillop
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p. 2185 - 2189
(2007/10/02)
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- Iron(III) perchlorate - A novel reagent in synthesis
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Iron (III) perchlorate in acetonitrile as the solvent converts alkohols and alkyl halides to acetamide derivatives, cleaves glycols and converts α-hydroxy acids to aldehydes or ketones.
- Kumar, Baldev,Kumar, Harish,Singh, N
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p. 460 - 461
(2007/10/02)
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- Preparation and Reactivities of Hexakisacetonitrile Iron(III) Perchlorate and Related Complexes as Strong Oxidizing Reagents
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The iron(III) complexes Fe(S)6(ClO4)3, S=solvent, were prepared from Fe(H2O)6(ClO4)3 in the donor solvents.Reactions of alkylbenzenes with Fe(AN)6(ClO4)3 (AN=acetonitrile) were explored because the AN complex has the highest formal redox potential, E0=1.73 V vs.SCE, among these complexes.Oxidation of the primary alkylbenzenes by the iron(III) AN complex gave the corresponding acetamides (Table II).Oxidation of the secondary alkylbenzenes, namely, cumene, 2-phenylbutane, and 2-exo-phenylnorbornane, afforded the corresponding acetates and acetamides (Charts 2 and 3), consuming over 4-mol eq of reagent.Reactions of p-xylene and hexamethylbenzene with Fe(CH2=CHCN)6(ClO4)3 also yielded the amides 31a and 31b.These results demonstrate the applicability of the iron(III) AN complexes as a powerful reagent to oxidize organic substrates which have onset potentials of anodic current of ca. 2.0 V vs.SCE.Keywords - oxidation; primary alkylbenzene; secondary alkylbenzene; oxidizing reagent; iron(III) perchlorate solvate; hexakisacetonitrile iron(III) perchlorate; hexakisacrylonitrile iron(III) perchlorate
- Kotani,Eiichi,Kobayashi, Shigeki,Ishii, Yoko,Tobinaga, Seisho
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p. 4281 - 4291
(2007/10/02)
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