- Synthesis of (alkoxycarbonyloxy)methyl, (acyloxy)methyl and (oxodioxolenyl)methyl carbamates as bioreversible prodrug moieties for amines
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Synthesis of (alkoxycarbonyloxy)methyl carbamates of secondary amines was developed, and it was extended to (acyloxy)methylation of benzylmethylamine and (oxodioxolenyl)methylation of benzylamine, benzylmethylamine, and L-phenylalanine.
- Li, Zhong,Bitha, Panayota,Lang Jr., Stanley A.,Lin, Yang-I
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- Remarkably Efficient Iridium Catalysts for Directed C(sp2)-H and C(sp3)-H Borylation of Diverse Classes of Substrates
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Here we describe the discovery of a new class of C-H borylation catalysts and their use for regioselective C-H borylation of aromatic, heteroaromatic, and aliphatic systems. The new catalysts have Ir-C(thienyl) or Ir-C(furyl) anionic ligands instead of the diamine-type neutral chelating ligands used in the standard C-H borylation conditions. It is reported that the employment of these newly discovered catalysts show excellent reactivity and ortho-selectivity for diverse classes of aromatic substrates with high isolated yields. Moreover, the catalysts proved to be efficient for a wide number of aliphatic substrates for selective C(sp3)-H bond borylations. Heterocyclic molecules are selectively borylated using the inherently elevated reactivity of the C-H bonds. A number of late-stage C-H functionalization have been described using the same catalysts. Furthermore, we show that one of the catalysts could be used even in open air for the C(sp2)-H and C(sp3)-H borylations enabling the method more general. Preliminary mechanistic studies suggest that the active catalytic intermediate is the Ir(bis)boryl complex, and the attached ligand acts as bidentate ligand. Collectively, this study underlines the discovery of new class of C-H borylation catalysts that should find wide application in the context of C-H functionalization chemistry.
- Chattopadhyay, Buddhadeb,Hassan, Mirja Md Mahamudul,Hoque, Md Emdadul
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supporting information
p. 5022 - 5037
(2021/05/04)
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- Application of Ag/TFPG-DMB COF in carbamates synthesis via CO2 fixation reaction and one-pot reductive N-formylation of nitroarenes under sunlight
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We have designed mesoporous AgNPs decorated COF (Ag/TFPG-DMB COF) nanomaterial which has been formed by an easy ex-situ synthetic method. The synthesized material is characterized by FTIR, PXRD, UV–vis, N2 adsorption–desorption studies, TEM, FESEM and XPS. The material showed the generation of identical mesopore at 3.9 nm. It is observed that the material can perform as both thermally and photochemically active catalyst for carbamate synthesis and one-pot reduction and N-formylation of nitroarenes respectively. The catalytic activity of the Ag/ TFPG-DMB COF nanomaterial is checked for green synthesis of carbamates from different amines and alcohols under 1 atmospheric pressure of CO2 with excellent yield (upto 95 %) as well as with high TOF value (182 h?1) and high selectivity. Additionally, the Ag/ TFPG-DMB COF nanomaterial is also applied as a potentially active photocatalyst for one-pot nitroarene reduction along with N-formylation reaction under sunlight irradiation in green reaction conditions with exceptionally high yield of formylated products upto 99 % as well as with high TOF value (762 h ?1). The catalyst efficiently reduced and formylated para-nitrophenol, a potential water pollutant, which elaborates its scope as an efficient catalyst for water purification also. The catalyst recyclability is also checked for five reaction cycles for both the reactions and the Ag/TFPG-DMB COF material showed outstanding recycling ability without any noticeable leaching of active metal or catalyst degradation.
- Biswas, Surajit,Hazra Chowdhury, Arpita,Hazra Chowdhury, Ipsita,Islam, Sk. Manirul
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- Evaluation of ethyl: N -(2-phenethyl) carbamate analogues as biofilm inhibitors of methicillin resistant Staphylococcus aureus
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A small molecule library consisting of 45 compounds was synthesized based on the bacterial metabolite ethyl N-(2-phenethyl) carbamate. Screening of the compounds revealed a potent analogue capabale of inhibiting several strains of Methicillin Resistant S. aureus biofilms with low to moderate micromolar IC50 values.
- Stephens, Matthew D.,Yodsanit, Nisakorn,Melander, Christian
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p. 6853 - 6856
(2016/07/21)
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- BMIm HCO3: an ionic liquid with carboxylating properties. Synthesis of carbamate esters from amines
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1-Butyl-3-methylimidazolium hydrogen carbonate (BMIm HCO3) was used as an ionic liquid with carboxylating properties able to convert, in the presence of an alkyl halide, amines into the corresponding carbamate esters. Moderate to good yields of
- Di Nicola,Arcadi,Rossi
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supporting information
p. 9895 - 9898
(2016/12/07)
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- An efficient one-pot synthesis of: N, N ′-disubstituted ureas and carbamates from N -acylbenzotriazoles
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A facile and high-yielding one-pot synthesis of carbamates and N,N′-disubstituted symmetrical ureas from N-acylbenzotriazoles has been devised. It is believed that, the intermediate acyl-azide undergo Curtius rearrangement and in different solvents gives different products i.e. carbamates in alcohols and N,N′-disubstituted symmetrical urea in THF.
- Singh, Anoop S.,Kumar, Dhananjay,Mishra, Nidhi,Tiwari, Vinod K.
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p. 84512 - 84522
(2016/10/12)
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- Heterobimetallic dinuclear lanthanide alkoxide complexes as acid-base bifunctional catalysts for synthesis of carbamates under solvent-free conditions
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Heterobimetallic dinuclear lanthanide alkoxide complexes Ln2Na8(OCH2CH2NMe2)12(OH)2 [Ln: I (Nd), II (Sm), III (Yb) and IV (Y)] were used as efficient acid-base bifunctional catalysts for the synthesis of carbamates from dialkyl carbonates and amines as well as the N-Boc protection of amines. The cooperative catalysts showed high catalytic activity and a wide scope of substrates with good to excellent yields under solvent-free conditions. The systems have shown higher catalytic activities due to the noteworthy synergistic interactions of Lewis acid center-Br?nsted basic center. The comparison of catalytic efficiency between mono- and dinuclear heterobimetallic lanthanide alkoxide analogues was also investigated.
- Zeng, Ruijie,Bao, Linquan,Sheng, Hongting,Sun, Lili,Chen, Man,Feng, Yan,Zhu, Manzhou
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p. 78576 - 78584
(2016/09/09)
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- N-Substituted carbamate synthesis using urea as carbonyl source over TiO2-Cr2O3/SiO2 catalyst
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The use of urea as an active form of carbon dioxide is a feasible way to substitute phosgene in the chemical industry. This paper reports an effective route for the synthesis of N-substituted carbamates from amines, urea and alcohols. Under the optimized reaction conditions, several important N-substituted carbamates were successfully synthesized in 95-98% yields over a TiO2-Cr2O3/SiO2 catalyst. The catalyst could be reused for several runs without deactivation. The catalysts were characterized by BET, XPS, XRD, and TPD, which suggested that the strength and amount of the acidic and basic sites might be the major reason for the high catalytic activity of TiO2-Cr2O3/SiO2.
- Wang, Peixue,Ma, Yubo,Liu, Shimin,Zhou, Feng,Yang, Benqun,Deng, Youquan
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p. 3964 - 3971
(2015/07/15)
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- Amide synthesis from alcohols and amines catalyzed by a RuII-N-heterocyclic carbene (NHC)-carbonyl complex
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Treatment of [Ru2(CO)4(CH3CN)6](BF4)2 with 3-methyl-1-(pyridin-2-yl)-imidazolium bromide in the presence of tetrabutylammonium bromide at room temperature in dichloromethane affords a RuII-N-heterocyclic carbene-carbonyl complex [Ru(py-NHC)(CO)2Br2] (1). Catalyst 1 displays diverse substrate scope for phosphine-free acceptorless coupling between alcohols and amines to amides at low catalyst loading. A RuII-dihydride/Ru0 sequence is proposed in the catalytic cycle.
- Saha, Biswajit,Sengupta, Gargi,Sarbajna, Abir,Dutta, Indranil,Bera, Jitendra K.
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p. 124 - 130
(2014/12/11)
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- Direct reductive amination using triethylsilane and catalytic bismuth(III) chloride
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Direct reductive amination (DRA) using triethylsilane (TESH) and catalytic bismuth(III) chloride (BiCl3) is described for the first time. The use of TESH and BiCl3 provides easy handling, low cost, non-toxicity, and a mild Lewis acid activity, thereby meeting the demand for green and sustainable chemistry. The developed DRA is highly chemoselective and applicable to less-basic amines. The experimental results of this study revealed that the developed DRA could be catalyzed by BiCl3, which was gradually reduced to Bi(0) or bismuth with a low valency by TESH, but TESCl, Bi(0), and Bi(0) with TESCl catalyzed the DRA to some extent.
- Matsumura, Takehiko,Nakada, Masahisa
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p. 1829 - 1834
(2014/03/21)
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- Convenient preparation of primary amides via activation of carboxylic acids with ethyl chloroformate and triethylamine under mild conditions
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Primary amides were easily prepared in 22-99% yields from the corresponding carboxylic acids 1 or 5 with NH4Cl via activation with ClCO 2Et and Et3N. The enantiomers of the corresponding primary amides of Cbz-, Boc-, or Fmoc-α-amino acids can be separated by using a chiral column.
- Noguchi, Takuya,Sekine, Masahiro,Yokoo, Yuki,Jung, Seunghee,Imai, Nobuyuki
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p. 580 - 582
(2013/07/05)
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- N -acyl DBN tetraphenylborate salts as N -acylating agents
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Air-stable and crystalline N-acyl DBN tetraphenylborate salts have been synthesized from 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) and the corresponding acyl chloride in the presence of sodium tetraphenylborate. The salts have been shown to be effective N-acylating agents, reacting with primary amines, secondary amines, and sulfonamides to form the corresponding N-acylated products in good yields. The DBN hydrotetraphenylborate byproduct can be conveniently removed by filtration, providing pure N-acylated products without the need for further purification. The N-acyl DBN tetraphenylborate salts are attractive alternatives to acyl halides as they can be stored in air without decomposition, avoid the production of free acid during acylation reactions, and can be used under more forcing thermal conditions.
- Taylor, James E.,Jones, Matthew D.,Williams, Jonathan M. J.,Bull, Steven D.
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experimental part
p. 2808 - 2818
(2012/04/23)
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- Redox self-sufficient biocatalyst network for the amination of primary alcohols
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Driving the machinery: A biocatalytic redox-neutral cascade for the preparation of terminal primary amines from primary alcohols at the expense of ammonia has been established in a one-pot one-step method (see picture). Applying this artificial biocatalyst network, long-chain 1,ω-alkanediols were converted into diamines, which are building blocks for polymers, in up to 99 % conversion. Copyright
- Sattler, Johann H.,Fuchs, Michael,Tauber, Katharina,Mutti, Francesco G.,Faber, Kurt,Pfeffer, Jan,Haas, Thomas,Kroutil, Wolfgang
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p. 9156 - 9159
(2012/10/30)
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- Heterogeneous CeO2 catalyst for the one-pot synthesis of organic carbamates from amines, CO2 and alcohols
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Heterogeneous CeO2 catalyst can catalyze the one-pot synthesis of methyl benzylcarbamate from benzylamine, CO2 and methanol. The yield of methyl benzylcarbamate reached 92% at >99% benzylamine conversion and 92% benzylamine-based selectivity even in the absence of the dehydrating agents. The catalyst is reusable after the calcination at 873 K for 3 h. Various carbamates can be synthesized with good yield and high selectivity by the reaction of amines + CO2 + alcohols over CeO2. The main formation route of methyl benzylcarbamate is suggested to be the reaction of dimethyl carbonate or the precursor of dimethyl carbonate formation with benzylamine.
- Honda, Masayoshi,Sonehara, Satoru,Yasuda, Hiroshi,Nakagawa, Yoshinao,Tomishige, Keiichi
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scheme or table
p. 3406 - 3413
(2012/01/15)
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- N-substituted carbamates syntheses with alkyl carbamates as carbonyl source over Ni-promoted Fe3O4 catalyst
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A series of catalysts of magnetic iron oxide containing Ni with different nickel content were prepared with co-precipitation method and tested in the syntheses of N-substituted carbamates from various amines and alkyl carbamates. Under the optimized reaction conditions, various N-substituted carbamates were successfully synthesized with 90-98% isolated yield. The catalyst could be recovered based on the magnetic property of the catalyst and reused for five runs without deactivation. The catalysts were characterized with X-ray photoelectron spectroscopy, X-ray diffraction, temperature-programmed reduction, temperature-programmed desorption, and Moessbauer spectroscopy analyses. The results showed that the catalytic activity may be derived from the delicate synergy between Ni and Fe species resulted in specific basic sites. Quasi in situ FT-IR and isotopic tracer revealed that the formation of substituted urea was the key step and the N-substituted carbamate was formed via further alcoholysis of the substituted urea.
- Shang, Jianpeng,Guo, Xiaoguang,Shi, Feng,Ma, Yubo,Zhou, Feng,Deng, Youquan
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experimental part
p. 328 - 336
(2011/05/14)
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- Structure-activity relationships of a small-molecule inhibitor of the PDZ domain of PICK1
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Recently, we described the first small-molecule inhibitor, (E)-ethyl 2-cyano-3-(3,4-dichlorophenyl)acryloylcarbamate (1), of the PDZ domain of protein interacting with Cα-kinase 1 (PICK1), a potential drug target against brain ischemia, pain and cocaine addiction. Herein, we explore structure-activity relationships of 1 by introducing subtle modifications of the acryloylcarbamate scaffold and variations of the substituents on this scaffold. The configuration around the double bond of 1 and analogues was settled by a combination of X-ray crystallography, NMR and density functional theory calculations. Thereby, docking studies were used to correlate biological affinities with structural considerations for ligand-protein interactions. The most potent analogue obtained in this study showed an improvement in affinity compared to 1 and is currently a lead in further studies of PICK1 inhibition.
- Bach, Anders,Stuhr-Hansen, Nicolai,Thorsen, Thor S.,Bork, Nicolai,Moreira, Irina S.,Frydenvang, Karla,Padrah, Shahrokh,Christensen, S. Brogger,Madsen, Kenneth L.,Weinstein, Harel,Gether, Ulrik,Stromgaard, Kristian
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supporting information; experimental part
p. 4281 - 4288
(2010/11/05)
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- Synthesis and antibacterial activity of isothiazolyl oxazolidinones and analogous 3(2H)-isothiazolones
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The synthesis and antibacterial activity of several new 5-((3-oxoisothiazol-2(3H)-yl)methyl)-3-phenyloxazolidin-2-ones 8 and analogous 2-(4-substituted phenyl)-3(2H)-isothiazolones 3 and 4 substituted at 4 and/or 3-positions of the phenyl moiety with different groups of which some have shown to increase the antibacterial activity of both 3-aryl-2-oxazolidinones and 3(2H)-isothiazolones is described. The most active compounds were isothiazolyl oxazolidinones 8a,j with unsubstituted and 8b with 4-F substituted phenyl rings which showed activities higher than analogous 3(2H)-isothiazolones and comparable or superior to linezolid, vancomycin, and ciprofloxacin against some tested microorganisms. The change in position of F and/or the use of larger substituents gave compounds with reduced or no activity. Evaluation of cytotoxicity to mouse fibroblast (NIH/3T3) cells indicated that these compounds exhibit antibacterial activity at non-cytotoxic concentrations.
- Adibpour, Neda,Khalaj, Ali,Rajabalian, Saeed
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scheme or table
p. 19 - 24
(2010/03/24)
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- Straightforward carbamoylation of nucleophilic compounds employing organic azides, phosphines, and aqueous trialkylammonium hydrogen carbonate
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In the presence of aqueous trialkylammonium hydrogen carbonate, the Staudinger reaction leads to the intermediate formation of the corresponding isocyanate, which, in turn, reacts further with a nucleophilic reagent also present in the mixture and results in carbamoylation with good yield. On the basis of this reaction a practical carbamoylation procedure was devised and a comparative study on suitability of different solvents and phosphorus (III) derivatives for carbamoylation reaction was conducted. The versatility of the method was demonstrated by examples with different classes of nucleophilic compounds that included the aminomethyl resin and natural compounds that display poor solubility in organic solvents.
- Yagodkin, Andrey,L?schcke, Kerstin,Weisell, Janne,Azhayev, Alex
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scheme or table
p. 2210 - 2221
(2010/04/29)
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- Effect of successive increase in alcohol chains on reaction with isocyanates and isothiocyanates
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The reaction of isocyanates and isothiocyanates with long-chain alcohols, e.g. n-hexanol, n-heptanol and n-octanol, exclusively gave N-aryl-O-alkyl carbamates, while N-aryl-O-alkyl carbamates were formed along with symmetrical 1,3-disubstituted ureas and thioureas when the same reactions were carried out with small-chain alcohols at room temperature without using any solvent.
- Perveen, Shahnaz,Yasmin, Arfa,Khan, Khalid Mohammed
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experimental part
p. 18 - 23
(2010/04/23)
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- Unmodified nano-powder magnetite catalyzes a four-component aza-Sakurai reaction
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A new catalyst for an old material: magnetite is an excellent Lewis acid catalyst for the four-component aza-Sakurai reaction. The process could be repeated up to 15-times without losing effectiveness, with the catalyst recycling being as easy as the use of a simple magnet. The catalyst is selective and could discriminate between aldehyde and ketone functionalities, catalyzing first the reaction with the higher electrophilic aldehyde.
- Martinez, Ricardo,Ramon, Diego J.,Yus, Miguel
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supporting information; experimental part
p. 1235 - 1240
(2009/05/30)
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- Iron-catalyzed four-component reaction for the synthesis of protected primary amines
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The first catalytic four-component reaction (4CR) of carbonyl compounds with alkyl chloroformate, HMDS and Et3SiH has been developed to produce protected primary amines by a novel tandem nitrogen protection/direct reductive amination of carbonyl compounds. In the presence of 5 mol-% of an iron(II) salt, a wide variety of aldehydes and ketones were transformed into their corresponding protected primary amines in good to excellent yields under "pure" multicomponent reaction (MCR) conditions. This chemistry was further extended to masked carbonyl compounds such as acetals, ketals, and vinyl ethers. When compared with previous methods to prepare protected primary amines from a large excess of ammonia or ammonium salts, this 4CR not only saved at least one step of synthetic manipulation, but also utilized nearly stoichiometric nitrogen and hydrogen sources and avoided the formation of (protected) secondary amines. Additional advantages of this protocol include broader substrate scope, the use of an inexpensive and environmentally friendly catalyst, and mild reaction conditions. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Yang, Bai-Ling,Tian, Shi-Kai
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p. 4646 - 4650
(2008/03/12)
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- Electrochemically promoted C-N bond formation from amines and CO 2 in ionic liquid BMIm-BF4: Synthesis of carbamates
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A new electrochemical procedure for the synthesis of organic carbamates from amines and carbon dioxide has been developed using selective cathodic reduction of carbon dioxide in CO2-saturated room-temperature ionic liquid BMIm-BF4 solutions containing amines 1a-j, followed by addition of EtI as an alkylating agent. The synthesis was carried out under mild (PCO2 = 1.0 atm, t = 55 °C) and safe conditions, and the use of volatile and toxic solvents and catalysts (according to the growing demand for ecofriendly synthetic methodologies), as well as of any supporting electrolyte (for a very easy workup of the reaction mixture), was avoided. Carbamates 2a-j were isolated in good to high yields.
- Feroci,Orsini,Rossi,Sotgiu,Inesi
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p. 200 - 203
(2007/10/03)
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- Reactions of cyclopropanone acetals with alkyl azides: Carbonyl addition versus ring-opening pathways
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(Chemical Equation Presented) The Lewis acid-mediated reactions of substituted cyclopropanone acetals with alkyl azides were found to strongly depend on the structure of the ketone component. When cyclopropanone acetal was treated with alkyl azides, N-substituted 2-azetidinones and ethyl carbamate products were obtained, arising from azide addition to the carbonyl, followed by ring expansion or rearrangement, respectively. When 2,2-dimethylcyclopropanone acetals were reacted with azides in the presence of BF3· OEt2, the products obtained were α-amino-α′- diazomethyl ketones, which arose from C2-C3 bond cleavage of the corresponding cyclopropanone, giving oxyallyl cations that were captured by azides. Aryl-substituted cyclopropanone acetals, when subjected to these conditions, afforded [1,2,3]oxaborazoles exclusively, which were also the result of C2-C3 bond rupture, azide capture, and then loss of nitrogen. In the reactions of n-hexyl-substituted cyclopropanone acetals with alkyl azides, a mixture of 2-azetidinones and regioisomeric [1,2,3]-oxaborazoles was obtained. The reasons for the different behavior of the various systems are discussed.
- Grecian, Scott,Desai, Pankaj,Mossman, Craig,Poutsma, Jennifer L.,Aube, Jeffrey
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p. 9439 - 9447
(2008/03/14)
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- Synthesis of carbamates and ureas using Zr(IV)-catalyzed exchange processes
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Equation presented Zirconium(IV)-catalyzed exchange processes have been developed to prepare both carbamates and ureas from dialkyl arbonates and carbamates employing 2-hydroxypyridine (HYP) and 4-methyl-2-hydroxyquinoline (MeHYQ) as catalytic additives, respectively A microwave acceleration effect was observed in Zr(IV)-catalyzed carbamate-urea exchange.
- Han, Chong,Porco Jr., John A.
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p. 1517 - 1520
(2008/02/02)
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- The design and synthesis of 9-phenylcyclohepta[d]pyrimidine-2,4-dione derivatives as potent non-nucleoside inhibitors of HIV reverse transcriptase
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Novel compounds, which can be considered as conformationally restricted analogues of MKC-442, have been synthesized and tested as inhibitors of the reverse transcriptase of human immunodeficiency virus type-1 (HIV-1). Reaction of urea with a β-ketoester furnished 6,7,8,9-tetrahydro-9-phenyl-1H- cyclohepta[d]pyrimidine-2,4-(3H,5H)-dione (6a) and 6,7,8,9-tetrahydro-9-p-tolyl- 1H-cyclohepta[d]pyrimidine-2,4-(3H,5H)-dione (6b) which were then alkylated at the N-1 position with chloromethyl ether, allyl bromide and benzyl bromide to afford the target compounds 7a-b, 8a-b, 9 and 10, respectively. The seven-membered, annelated compounds have a relatively rigid structures and can lock the orientation of the aromatic ring. Chemical modification at N-1 of the pyrinidine ring and the 9-phenyl ring was attempted, with the aim of improving the antiretroviral activity. In particular, replacement of the aliphatic group with the phenyl moiety at the terminus of N-1 side chain can enhance the activity. The most active compounds showed activity in the low micromolar range with IC50 values comparable to that of nevirapine. The biological activity results are in accordance with the docking results. The Royal Society of Chemistry 2006.
- Wang, Xiaowei,Lou, Qinghua,Guo, Ying,Xu, Yang,Zhang, Zhili,Liu, Junyi
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p. 3252 - 3258
(2008/03/13)
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- Pd(OAc)2-catalyzed carbonylation of amines
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A phosphine-free catalytic system [Pd(OAc)2-Cu(OAc) 2-air] induced a substrate-specific carbonylation of amines in boiling toluene under CO gas (1 atm). Symmetrical N,N′-dialkylureas were obtained by the carbonylation of primary amines. N,N,N′-Trialkylureas were selectively formed by addition of a secondary amine to the above reaction vessel. Secondary amines did not give tetraalkylureas. However, dialkylamines with a phenyl group on their alkyl chains, such as N-monoalkylated benzylic amine or phenethylamine derivatives, underwent a direct aromatic carbonylation to afford five- or six-membered benzolactams. In the carbonylation, the chelation effect or steric repulsion between Pd(II) and the meta-substituent in the ortho-palladation and the ring sizes of cyclopalladation products that were formed prior to carbonylation were found to generate good site selectivity and increase the reaction rate. In contrast, carbonylation of ω- arylalkylamines with a hydroxyl group gave neither ureas nor benzolactams but instead produced 1,3-oxazolidinones smoothly. Hydrochlorides of amines also underwent carbonylation to afford the corresponding amides under the conditions used. This procedure made it possible to prepare ureas of amino acid esters and N-alkylcarbamates in practical yields.
- Orito, Kazuhiko,Miyazawa, Mamoru,Nakamura, Takatoshi,Horibata, Akiyoshi,Ushito, Harumi,Nagasaki, Hideo,Yuguchi, Motoki,Yamashita, Satoshi,Yamazaki, Tetsuro,Tokuda, Masao
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p. 5951 - 5958
(2007/10/03)
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- N-acyl and N-alkoxycarbonyl derivatives of 1H-1,2,3-triazolo-[4,5-c] pyridine; preparation and application
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The N-acylating and N-alkoxycarbonylation ability of the N-substituted 1,2,3-triazolo[4,5-c]pyridines 1a-e have been investigated. The alkoxycarbonyl triazolopyridine derivatives (1c-e) were readily prepared in 81-96% yield (the corresponding tetrafluoroborate > 95%). Triazolo[4,5-c]pyridine (1) has been shown to work as a good leaving group by the formation of amido- and carbamate protected derivatives of primary amines. The method was also successful for the N-tert-butoxycarbonyl (N-BOC) protection of the amino acid, phenylalanine. The synthetic transformations are facilitated by the one-pot preparation of 1a-e followed by the direct reaction with the amines or amino acid. The present method thus offers an efficient and convenient protocol for the in situ preparation of triazolopyridine reagents to be used directly for the protection of amines and amino acids. N-Acyl- and N-alkoxycarbonyl triazolopyridines (1a-e) were readily prepared in 4 steps from 4-aminopyridine (4) by amine protection, pyridine nitration, nitro reduction and diazotizations/cyclizations. All reactions offer the advantages of rapid conversions in high yields under very mild conditions.
- Holt, Jarle,Fiksdahl, Anne
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p. 417 - 423
(2007/10/03)
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- Synthesis of Carbamates Using Yttria-Zirconia Based Lewis Acid Catalyst
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A variety of amines react with chloroformates in the presence of catalytic amount of yttria-zirconia based catalyst to afford the corresponding carbamates in excellent yields.
- Pandey, Rajesh K.,Dagade, Sharda P.,Dongare, Mohan K.,Kumar, Pradeep
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p. 4019 - 4027
(2007/10/03)
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- Cyanomethyl anion/carbon dioxide system: An electrogenerated carboxylating reagent. Synthesis of carbamates under mild and safe conditions
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A new carboxylating reagent (-CH2CN/CO2) was obtained by bubbling CO2 in a CH3CN-TEAP (tetraethylammonium perchlorate) solution previously electrolyzed under galvanostatic control. Organic carbamates were isolated from these solutions after addition of amines and an alkylating agent. In this paper, we describe the optimized conditions for the electrochemical synthesis of carbamates from amines and CO2, in mild and safe conditions, without any addition of bases, probases, or catalysts. Carbamates were isolated from primary and secondary aliphatic amines in high to excellent yields and from aromatic amines in moderate yields (dependent on the nucleophilicity of the nitrogen atom).
- Feroci, Marta,Casadei, Maria Antonietta,Orsini, Monica,Palombi, Laura,Inesi, Achille
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p. 1548 - 1551
(2007/10/03)
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- Synthetic and structural studies on 1,2,4-dithiazolidine-3,5-dione derivatives
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Methods have been developed for the N-alkylation of 1,2,4-dithiazolidine-3,5-dione 2 and the subsequent conversion of the N-alkylated derivatives into isocyanates 5. An extension of this methodology onto a solid-support is also reported. X-ray crystallographic analysis has been carried out on potassium 1,2,4-dithiazolidine-3,5-dione 3 for structural comparison with the parent heterocycle 2.
- Wood, Mark E.,Cane-Honeysett, Daniel J.,Dowle, Michael D.,Coles, Simon J.,Hursthouse, Michael B.
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p. 3015 - 3023
(2007/10/03)
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- Catalytic activity of MCM-41-TBD in the selective preparation of carbamates and unsymmetrical alkyl carbonates from diethyl carbonate
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The synthesis of carbamates 3 and unsymmetrical alkyl carbonates 5 by reaction of diethyl carbonate with aliphatic amines or alcohols has been realized by using as heterogeneous catalyst a hybrid organic-inorganic material prepared by anchoring TBD to MCM-41 silica. Products are obtained in high yield and very good selectivity and the solid catalyst can be recovered simply by filtration and reused for different cycles without apparent lowering of activity. A supported N -carbethoxyguanidinium active intermediate is proposed, and some spectroscopic data are shown to support the mechanistic hypothesis.
- Carloni, Silvia,De Vos, Dirk E.,Jacobs, Pierre A.,Maggi, Raimondo,Sartori, Giovanni,Sartorio, Raffaella
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p. 199 - 204
(2007/10/03)
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- Traceless synthesis of urea, semicarbazide and carbamate derivatives using Bromo-Wang resin and Bromo-Wang SynPhase Lantern
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Traceless synthesis of urea, semicarbazide and carbamate derivatives has been carried out successfully on bromo-Wang resin and SynPhase Lantern. The synthetic route is simple and convenient to perform. Most of the products are obtained in high yields and purities after acidic cleavage.
- Phoon, Chee Wee,Sim, Mui Mui
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p. 697 - 699
(2007/10/03)
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- Kinetics and mechanism of the aminolysis of O-ethyl S-aryl thiocarbonates in acetonitrile
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The Kinetics and mechanism of the reactions of O-ethyl S-(Z)aryl thiocarbonates with (X)benzylamines in acetonitrile at 45.0 °C are studied. Relatively small values of βx (βnuc) = 0.6 to approximately 0.8 and βz (βlg) = -0.5 to approximately -0.7 together with a negative cross-interaction constant ρxz (= -0.47) and failure of the reactivity-selectivity principle (RSP) are interpreted to indicate a concerted mechanism. The normal kinetic isotope effects (kH/kD = 1.3 to approximately 1.8) involving deuterated benzylamine nucleophiles suggest a hydrogen-bonded, four-center-type transition state.
- Oh, Hyuk Keun,Lee, Yun Ho,Lee, Ikchoon
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p. 131 - 135
(2007/10/03)
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- The reaction of amines with an electrogenerated base. Improved synthesis of arylcarbamic esters
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The electrogenerated base of 2-pyrrolidone reacts with amines and anilines yielding the corresponding alkyl and aryl carbamates, after addition of carbon dioxide and ethyl iodide. Arylcarbamic esters are obtained in very good yields under mild reaction conditions with respect to the methods so far reported. (C) 2000 Elsevier Science Ltd.
- Feroci, Marta,Inesi, Achille,Rossi, Leucio
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p. 963 - 966
(2007/10/03)
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- 1,2,4-Dithiazolidine-3,5-dione: A nucleophilic isocyanate 'building block'
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Mild conditions are described for the direct N-alkylation of 1,2,4-dithiazolidine-3,5-dione 1 using a variety of alkyl halides with subsequent conversion of the products 2 into alkyl isocyanates using triphenylphosphine.
- Cane-Honeysett,Dowle,Wood
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p. 1622 - 1624
(2007/10/03)
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- Direct conversion of azides to carbamates and sulfonamides using Fe/NH4Cl: Effect of sonication
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A simple, direct and effective conversion of azides to carbamates and sulfonamides is achieved using Fe/NH4Cl in methanol. The influence of sonication and direct application in solution phase combinatorial chemistry are also studied by developing a 6x4 matrix library. (C) 2000 Elsevier Science Ltd.
- Chandrasekhar,Narsihmulu
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p. 7969 - 7972
(2007/10/03)
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- Kinetics and mechanism of the aminolysis of ethyl aryl carbonates in acetonitrile
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The aminolysis reactions of ethyl aryl carbonates with benzylamines in acetonitrile at 25.0°C are investigated. The base-catalyzed path, k2, disappears when strong nucleophiles (X = p-CH3O and p-CH3) react with a substrate activated by a strong nucleofuge (Z = p-NO2). The large magnitude of ρ(x) (-1.7 to -2.5), ρ(z) (3.4 to 4.3), and ρ(xz) (1.4) values, and relatively large k(H)/k(D) (1.6 to 1.8) found for the uncatalyzed path (k1) can be accounted for in terms of a stepwise mechanism with rate-limiting expulsion of the phenoxide leaving group. The catalyzed process (k2) is characterized by the much smaller magnitude of ρ(x) (-1.0 to -1.7), ρ(z) (0.4 to 0.7), and ρ(xz) (0.2), the larger k(H)/k(D) (2.1 to 2.5) values, and the lower ΔH(+) values (1.8-1.9 kcal mol-1) than those of the uncatalyzed process (k1) with large negative ΔS(+) values (-65 to -67 cal K-1 mol- 1). These results are consistent with four- and six-centered transition states for the two processes, k1 and k2, respectively.
- Koh, Han Joong,Lee, Ji-Won,Lee, Hai Whang,Lee, Ikchoon
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p. 710 - 716
(2007/10/03)
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- New facile alkoxycarbonylating agent, alkyl pyrazole-1-carboxylates. The preparation and the utilities
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Alkyl pyrazole-1-carboxylates (2), which were readily prepared from alkyl chloroformate or carbazate in good yields, were provided as the new facile alkoxycarbonylating agents toward the Grignard reagents for the synthesis of one carbon higher carboxylic esters. Also amines were alkoxycarbonylated by 2 to produce the corresponding urethanes even in an aqueous medium. Benzyl 3,5-dimethylpyrazole-1-carboxylate (2d) could be utilized for the Cbz-protection of amino acids and esters in good yield without any racemization.
- Kashima, Choji,Tsuruoka, Shiro,Mizuhara, Saori
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p. 14679 - 14688
(2007/10/03)
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- A versatile synthon for chemoselective N-acylation reagents, 2-fluoro-N-mesylaniline
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2-Fluoro-N-mesylaniline 3b undergoes various N-acylalions easily to give 2-fluoro-N-acyl-N-mesylanilines 4b-8b, which function as good chemoselective N-acylation reagents, especially for benzyloxycarbonylation.
- Kondo, Kazuhiro,Sekimoto, Erika,Miki, Kazuki,Murakami, Yasuoki
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p. 2973 - 2974
(2007/10/03)
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- Electrogenerated Superoxide-Activated Carbon Dioxide. A New Mild and Safe Approach to Organic Carbamates
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The electrochemical reduction of O2 (E = -1.0 V vs SCE) in dipolar aprotic solvents in the presence of CO2 gave a carboxylating reagent (O2·-/CO2) able to convert amines and different types of their derivatives into carbamates. Primary and secondary aliphatic and aromatic amines were converted into the corresponding ethyl carbamates by the addition of EtI to the carbamate anions generated in the first step of the reactions. The yields were dependent on the nucleophilicity of the nitrogen atom ω-Bromoethyl- and propylamine gave 2-oxazolidinone and tetrahydro-l,3-oxazm-2-one in moderate yields. N-Acyl or N-(alkoxycarbonyl)alkylamines bearing a leaving group at the β position of the alkyl substituent were converted into 3-substituted-2-oxazolidinones in high yields. By using chiral substrates, enantiopure 3-alkoxycarbonyl(or acyl)-4-substituted oxazolidin-2-ones (70-85% isolated yields) were obtained. This represents a new mild and safe route to these important auxiliaries for asymmetric synthesis. Some limitations of the process are also evidenced and accounted for.
- Casadei, Maria Antonietta,Moracci, Franco Micheletti,Zappia, Giovanni,Inesi, Achille,Rossi, Leucio
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p. 6754 - 6759
(2007/10/03)
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- Specificity of DNA alkylation by 1-(2-chloroethyl)-3-alkyl-3- acyltriazenes depends on the structure of the acyl group: Kinetic and product studies
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The reactions of calf thymus DNA with ten 1-(2-chloroethyl)-3-alkyl-3- acyltriazenes of varying acyl side chain structure were studied alone, or in the presence of porcine liver esterase in pH 7.0 phosphate buffer. In several of the key triazenes, the acyl substituent contained a free carboxylic acid group. With esterase present in the reaction mixture, the resultant levels of DNA alkylation could be correlated with the kinetic rates of decomposition of the triazenes. Under these conditions, the predominant pathway of decomposition involved deacylation of the parent triazene and eventual production of an alkanediazonium ion. This intermediate subsequently alkylated DNA-guanine to give 7-alkylguanine as the principal reaction product. In the absence of esterase, the order of DNA alkylation for all of the acyltriazenes did not correlate with their respective rates of decomposition, leading to the conclusion that the triazenes did not decompose by the expected mode of uncatalyzed N(2)-N(3) heterolyic cleavage. The major DNA alkylation product from the N(3)-methyltriazenes was 7-methylguanine, instead of the expected 7-(chloroethyl)- and 7-(hydroxyethyl)guanine products, which suggested that the acyl group was being hydrolyzed. However, acyltriazenes with an N(3)-benzyl group rather than a methyl in this position produced very little 7-benzylguanine product, contrary to prediction. An alternative mechanism involving internally assisted hydrolysis of the side chain ester is proposed to explain these results. NMR product analysis and computational studies were carried out to lend support to the postulated mechanism.
- Smith,Schmidt,Czerwinski,Taneyhill,Snyder,Kline,Michejda,Smith Jr.
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p. 466 - 475
(2007/10/03)
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- Electrochemical activation of carbon dioxide: Synthesis of carbamates
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Electrochemically activated CO2 reacts with amines and EtI under mild reaction conditions affording the corresponding carbamates in high to excellent yields.
- Casadei, Maria A.,Inesi, Achille,Moracci, Franco Micheletti,Rossi, Leucio
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p. 2575 - 2576
(2007/10/03)
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- Chemoselective Reactions of Tellurium Tetraethoxide towards Thioamides and Amides
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Tellurium tetraethoxide reacts with primary thioamides at room temperature, forming nitriles in high yields. On the other hand, the reactions with amides are largely temperature-dependent, giving predominantly esters at 80 deg C and nitriles at a higher temperature. Similarly, tellurium tetraethoxide readily induces the C-N bond cleavage of ureas to give carbamates and amines.
- Omote, Kazushi,Aso, Yoshio,Otsubo, Tetsuo,Ogura, Fumio
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p. 1759 - 1761
(2007/10/02)
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- Nucleophilic Attack vs General Base Assisted Hydrolysis in the Reactions of Acetic Anhydride with Primary and Secondary Amines. pH-Yield Studies in the Recognition and Assessement of the Nucleophilic and General Base Reactions
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The reaction of a set of primary and secondary amines with acetic anhydride in water at 25 deg C gave variable yields of the N-substituted acetamide in seven of the eight amines studied.The yield of the amide as a function of pH revealed the incursion in the most cases of a general base assisted hydrolysis of the acetic anhydride by the amine.From the pKa's of the amines and kw and kOH for acetic anhydride (the specific rates for the reaction of the anhydride with water and hydroxide, respectively), both kDN (for the formation of acetamides) and kGB (for the general base assisted hydrolysis) may be readily evaluated by fitting the pH-yield-data to pH-yield or pH-product ratio profiles.The reactions of ethyl chloroformate with aniline and benzylamine in water also showed the presence of the general base assisted reaction.It is concluded that (a) pH-yield data provide a new way of showing the existence of general base assisted hydrolysis in the presence of a direct nucleophilic displacement reaction, (b) the general base promoted reaction is sufficiently prevalent that it would be prudent to check specifically for its presence in any investigation of mechanisms of acyl transfer in water, and (c) until the extent of general base promoted hydrolysis can be predicted adequately, the possibility of such a reaction makes it difficult to predict yields of the products of the direct attack, and hence just how suitable a medium water may be for a particular preparative acyl transfer reaction.
- King, James F.,Guo, Zhen Rong,Klassen, Darryl F.
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p. 1095 - 1101
(2007/10/02)
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- AMINO ACID DERIVATIVES CYCLIZED AT THE C-TERMINAL
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Novel α-substituted Trp dipeptoid derivatives cyclized at the C-terminal useful as agents in the treatment of obesity, hypersecretion of gastric acid in the gut, gastrin-dependent tumors, or as antipsychotics are disclosed. Further, the compounds are antianxiety agents and antiulcer agents. They are agents useful for preventing the response to the withdrawal from chronic treatment with or use of nicotine, diazepam, alcohol, cocaine, caffeine, or opioids. The compounds of the invention are also useful in treating and/or preventing panic attacks. Also disclosed are pharmaceutical compositions and methods of treatment using the compounds as well as processes for preparing them and novel intermediates useful in their preparation. An additional feature of the invention is the use of the compounds in diagnostic compositions.
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- Intermolecular reactions of N-alkoxycarbonyliminium ions with propargyltrimethylsilane; oxazinone versus allene formation
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Intermolecular reactions of N-alkoxycarbonyliminium ions with propargyltrimethylsilane mainly lead to 6-(trimethylsilyl)methyl-3,4-dihydro-2H-1,3-oxazinones, formed by intramolecular trapping of a stabilized β-sily vinylic cation. α-Allenyl carbamates are obtained as minor products. The oxazinone/allene ratio is dependent on the nature of the Lewis acid and the solvent used.
- Esch,Hiemstra,Speckamp
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p. 3445 - 3462
(2007/10/02)
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- DICHLORONITROACETIC ACID DERIVATIVES AS ACYLATING AGENTS FOR PRIMARY AMINES, AMMONIA, AND PHENYLHYDRAZINE
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The corresponding carbamic acid derivatives were obtained (28-91percent) yields) as a result of the reaction of dichloronitroacetic acid derivatives, O2NCCl2COR, (1a-c, R=OEt, OCH2Ph, NH2) with ammonia, methylamine, benzylamine, glycine, phenylhydrazine, and aniline. The probable mechanism of the process and factors that affect the nature of the departing group were discussed. Keywords: dichloronitroacetic acid derivatives, aminolysis, intermediate states, mechanisms of reactions.
- Yurtanov, A. I.,Adkhamova, Z. M.,Baidildaeva, S. K.
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p. 891 - 894
(2007/10/02)
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