- Synthesis and characterisation of polyamide dendrimers with systematically varying surface functionality
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Remarkable changes of properties result from systematically varying the surface functionality of polyamide dendrimers within a single generation. The Royal Society of Chemistry 2009.
- Willcock, Helen,Cooper, Andrew I.,Adams, Dave J.,Rannard, Steve P.
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Read Online
- Probing the mid-gorge of cholinesterases with spacer-modified bivalent quinazolinimines leads to highly potent and selective butyrylcholinesterase inhibitors
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The spacer structure of homobivalent quinazolinimes acting as potent acetyl-(AChE)- and butyrylcholinesterase (BChE) inhibitors was chemically modified introducing tertiary amine and acyl-amide moieties, and the activities at both ChEs were evaluated. Molecular docking was applied to explain the data and probe the capacity of the mid-gorge site of both ChEs. The novel spacer structures considerably alter the biological profile of bivalent quinazolinimines with regard to both inhibitory activity and selectivity. Mutual interaction of binding to the various sites of the enzymes was further investigated by applying also different spacer lengths and ring sizes of the alicycle of the tricyclic quinazolinimines. In order to achieve selectivity toward BChE and to improve inhibitory activities, the spacer structure was optimized and identified a highly potent and selective BChE inhibitor.
- Chen, Xinyu,Tikhonova, Irina G.,Decker, Michael
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Read Online
- Solvent-freeN-Boc deprotection byex situgeneration of hydrogen chloride gas
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An efficient, scalable and sustainable method for the quantitative deprotection of thetert-butyl carbamate (N-Boc) protecting group is described, using down to near-stoichiometric amounts of hydrogen chloride gas in solvent-free conditions. We demonstrate theex situgeneration of hydrogen chloride gas from sodium chloride and sulfuric acid in a two-chamber reactor, introducing a straightforward method for controlled and stoichiometric release of HCl gas. The solvent-free conditions allow deprotection of a wide variety ofN-Boc derivatives to obtain the hydrochloride salts in quantitative yields. The procedure obviates the need for any work-up or purification steps providing an uncomplicated green alternative to standard methods. Due to the solvent-free, anhydrous conditions, this method shows high tolerance towards acid sensitive functional groups and furnishes expanded functional group orthogonality.
- De Borggraeve, Wim M.,Gilles, Philippe,Van Mileghem, Seger,Verschueren, Rik H.
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supporting information
p. 5782 - 5787
(2021/07/12)
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- Enantioselective Syntheses of Strychnos and Chelidonium Alkaloids through Regio- and Stereocontrolled Cooperative Catalysis
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We describe enantioselective syntheses of strychnos and chelidonium alkaloids. In the first case, indole acetic acid esters were established as excellent partner nucleophiles for enantioselective cooperative isothiourea/Pd catalyzed α-alkylation. This provides products containing indole-bearing stereocenters in high yield and with excellent levels of enantioinduction in a manner that is notably independent of the N-substituent. This led to concise syntheses of (?)-akuammicine and (?)-strychnine. In the second case, the poor performance of ortho-substituted cinnamyl electrophiles in the enantioselective cooperative isothiourea/Ir catalyzed α-alkylation was overcome by appropriate substituent choice, leading to enantioselective syntheses of (+)-chelidonine, (+)-norchelidonine, and (+)-chelamine.
- Fyfe, James W. B.,Hutchings-Goetz, Luke S.,Snaddon, Thomas N.,Yang, Chao
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supporting information
p. 17556 - 17564
(2020/08/14)
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- Organic/inorganic Fe3O4@MCM-41@Zr-piperazine: An impressive magnetite nanocatalyst for N-Tert-Butoxycarbonylation of amines
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Fe3O4@MCM-41@Zirconium magnetic nanoparticles modified with piperazine (Fe3O4@MCM-41@Zr-piperazine), as a newly reported catalyst, shows excellent catalytic activity in N-tertbutoxycarbonylation of amines under the mild and solvent-free conditions. Accordingly, different derivatives of N-tert-butylcarbamates owning diverse aliphatic, aromatic and heteroaromatic amines were prepared efficiently. Good performance of this method for the majority of used complex or acidsensitive substrates and facile separation of this nanocatalyst due to its superparamagnetic nature from the reaction mixture via an external magnetic field for several times are the most important striking features of this protocol.
- Pourhasan-Kisomi, Reyhaneh,Shirini, Farhad,Golshekan, Mostafa
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p. 3859 - 3870
(2019/05/08)
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- Preparation method of (2-methylamine-ethyl)-tert-butyl carbamate
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The invention discloses a preparation method of (2-methylamine-ethyl)-tert-butyl carbamate, and belongs to the technical field of organic chemical synthesis. The preparation method comprises followingsteps: 1, imidazole is dissolved in dichloromethane, and di-tert-butyl dicarbonate ester is added at room temperature, reaction is carried out for 2 to 3h at room temperature, and water washing drying are carried out so as to obtain an intermediate; and 2, the intermediate is dissolved in toluene, N-methylethylenediamine is added, an obtained mixture is heated to 60 to 70 DEG C, reaction is carried out for 2 to 4h, reduced pressure distillation is carried out to remove toluene, and purification is carried out so as to obtain (2-methylamine-ethyl)-tert-butyl carbamate. The operation steps arefew; by-product content is reduced with ensured (2-methylamine-ethyl)-tert-butyl carbamate synthesis yield; cost is relatively low; and batch production requirements are satisfied.
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Paragraph 0024; 0026; 0028
(2019/07/01)
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- LIPID DELIVERY OF THERAPEUTIC AGENTS TO ADIPOSE TISSUE
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A method of treating a disease mediated by protein expression in adipose tissue by intraperitoneally administering a composition comprising a lipid nanoparticle encapsulating or associated with a therapeutic agent (e.g., a nucleic acid), thereby delivering the therapeutic agent to adipose tissue of the subject and altering protein expression in the adipose tissue is provided herein. A method for delivering a therapeutic agent to adipose tissue of a subject in need thereof is also provided.
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Page/Page column 169-170
(2018/11/10)
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- BRANCHED POLYESTER CARRYING DENDRONS
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Branched polyesters carrying dendrons are a useful class of nanomaterials which exhibit good handling properties and stability, can degrade to a high extent, and are effective encapsulation materials. They can be used to make nanoprecipitated particles which may for example be used in therapy. Furthermore, these materials can be synthesised by economical and tailorable processes. The materials can be prepared by the ring-opening polymerisation (ROP) of monofunctional lactone monomers and difunctional lactone monomers, using dendron initiators.
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Page/Page column 9-10
(2017/07/28)
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- Chemoselective acylation of 2-amino-8-quinolinol in the generation of C2-amides or C8-esters
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Two different ways to carry out the chemoselective acylation of 2-amino-8-quinolinol with unique features to generate C2-amides or C8-esters were developed. The coupling reaction with a variety of carboxylic acids using EDCI and DMAP provided C8-ester derivatives, whereas N-heteroaromatic acids were not introduced on the C8-hydroxy group, but rather on the C2-amino group under the same conditions. To obtain C2-amides selectively, the anionic nucleophile from 2-amino-8-quinolinol was treated with less reactive acyl imidazolides or esters.
- Park, Yongseok,Fei, Xiang,Yuan, Yue,Lee, Sanha,Hur, Joonseong,Park, Sung Jean,Jung, Jae-Kyung,Seo, Seung-Yong
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p. 41955 - 41961
(2017/09/12)
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- Copper nanoparticles catalyzed N-H functionalization: An efficient solvent-free N-tert-butyloxycarbonylation strategy
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A chemoselective transformation of amines to their tert-butyloxycarbonyl (Boc) protected derivatives (NBoc) is described using Cu-NPs under solvent-free conditions. Simple method, rapid reaction rate, mild conditions, tolerance of a wide range of functional groups, excellent yield, ease recovery and high catalytic turnover are the salient features of this approach. tert-Butyloxycarbonylation of chiral amino acid esters and amino alcohols were performed without racemization.
- Deb, Barnali,Debnath, Sudipto,Deb, Anindita,Maiti, Dilip K.,Majumdar, Swapan
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supporting information
p. 629 - 633
(2017/01/25)
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- Preparation, characterization and application of 1,4-disulfopiperazine-1,4-diium chloride ([Piper-(SO3H)2]·2Cl) as an efficient dicationic ionic catalyst for the N-Boc protection of amines
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In this work, 1,4-disulfopiperazine-1,4-diium chloride ([Piper-(SO3H)2]·2Cl), as a novel Br?nsted acidic ionic catalyst is synthesized and characterized using a series of techniques including FT-IR, TGA, DTA, SEM, pH analysis and Hammett acidity function. This substance can significantly catalyze the N-Boc protection of amines without solvent interference at room temperature. The advantages of this manner are chemoselectivity, short reaction times, suitable yields, excellent yields of the products, without solvent interference and ease of preparation as well as reusability of the catalyst.
- Koodehi, Tahereh Ghauri,Shirini, Farhad,Goli-Jolodar, Omid
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p. 443 - 456
(2017/01/10)
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- POLYIMIDE PRECURSOR COMPOSITION AND PREPARATION METHOD AND USE THEREOF
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The present invention provides a polyimide precursor composition comprising a polyimide precursor and a thermal base generator having the structure of formula (1): wherein R1, R2, R3, R4, R5 and are as defined in the specification. The present invention also provides a polyimide prepared from the aforementioned precursor composition, and a preparation method thereof.
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Page/Page column 19; 20
(2016/10/09)
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- An efficient chelator for complexation of thorium-227
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We present the synthesis and characterization of a highly efficient thorium chelator, derived from the octadentate hydroxypyridinone class of compounds. The chelator forms extremely stable complexes with fast formation rates in the presence of Th-227 (ambient temperature, 20?min). In addition, mouse biodistribution data are provided which indicate rapid hepatobiliary excretion route of the chelator which, together with low bone uptake, supports the stability of the complex in vivo. The carboxylic acid group may be readily activated for conjugation through the ?-amino groups of lysine residues in biomolecules such as antibodies. This chelator is a critical component of a new class of Targeted Thorium Conjugates (TTCs) currently under development in the field of oncology.
- Ramdahl, Thomas,Bonge-Hansen, Hanne T.,Ryan, Olav B.,Larsen, ?smund,Herstad, Gunnar,Sandberg, Marcel,Bjerke, Roger M.,Grant, Derek,Brevik, Ellen M.,Cuthbertson, Alan S.
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supporting information
p. 4318 - 4321
(2016/08/18)
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- Synthesis, nanoprecipitation and pH sensitivity of amphiphilic linear-dendritic hybrid polymers and hyperbranched-polydendrons containing tertiary amine functional dendrons
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The combination of linear polymers with dendritic chain-ends has led to numerous studies of linear-dendritic polymer hybrid materials. Interchain branching within the linear segment of these materials has recently extended this concept to the formation of soluble hyperbranched-polydendrons. Here, the introduction of amphiphilicity into hyperbranched-polydendrons has been achieved for the first time through the use of tertiary amine functional dendritic chain-ends and branched hydrophobic polymer segments. The synthesis and aqueous nanoprecipitation of these branched materials is compared with their linear-dendritic polymer analogues, showing that chain-end chemistry/generation, precipitation medium pH and polymer architecture are all capable of influencing the ability to generate nanoparticles, the resulting nanoparticle diameter and dispersity, and subsequent response to changes in pH.
- Rogers, Hannah E.,Chambon, Pierre,Auty, Sam E. R.,Hern, Faye Y.,Owen, Andrew,Rannard, Steve P.
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p. 7005 - 7015
(2015/09/07)
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- Preparation, characterization and application of succinimidinium hydrogensulfate ([H-Suc]HSO4) as an efficient ionic liquid catalyst for the N-Boc protection of amines
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In this work, succinimidinium hydrogensulfate ([H-Suc]HSO4), as a novel Bronsted acidic ionic liquid is prepared and characterized by studying its FT-IR, 1H NMR, 13C NMR, mass and SEM. This reagent can be used as an efficient catalyst for the N-Boc protection of amines at room temperature and neat conditions. This new method consistently has the advantages of excellent yields and short reaction times. Further, this ionic liquid can be recovered and reused for several times. This journal is
- Shirini, Farhad,Jolodar, Omid Goli,Seddighi, Mohadeseh,Borujeni, Hojatollah Takbiri
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p. 19790 - 19798
(2015/03/18)
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- MgBr 2 · OEt 2: A Lewis Acid Catalyst for the O - And N -Boc Protection of Phenols and Amines
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MgBr2 · OEt2 efficiently catalyzes the O- and N-tert-butoxycarbonylation of functionalized phenols and amines. The presented procedure is operationally simple and done under solvent-free conditions. GRAPHICAL ABSTRACT.
- Schechter, Aaron,Goldrich, David,Chapman, Jessica R.,Uberheide, Beatrix M.,Lim, Daniel
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supporting information
p. 653 - 660
(2015/10/29)
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- POLYDENDRONS
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A method of preparing a non-gelled branched vinyl polymer scaffold carrying dendrons, comprising the living or controlled polymerization of a monofunctional vinyl monomer and a difunctional vinyl monomer, using a dendron initiator and at least one further initiator.
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Page/Page column 31; 32
(2015/01/09)
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- General solvent-free highly selective N-tert-butyloxycarbonylation strategy using protic ionic liquid as an efficient catalyst
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A simple, rapid and solvent-free protocol is described for the chemo-selective transformation of amines to tert-butyloxycarbonyl protected derivatives (NHBoc) using Boc2O and imidazolium trifluoroacetate protic ionic liquid (5-20 mol%). Unwanted side products such as isocyanate, urea or N,N-di-Boc were not detected. The scope of the protection strategy was successfully explored for substrate alcohols, phenols and thiol at elevated temperatures. Optically pure amino acids, amino acid esters and amino alcohols were efficiently converted to the corresponding N-Boc protected derivatives in excellent yields without racemization at the chiral center. The distinct advantages of this method are: operational simplicity, cleaner reaction, high selectivity, excellent yield, rapid reaction convergence, easy preparation and recyclability of the catalyst.
- Majumdar, Swapan,De, Jhinuk,Chakraborty, Ankita,Maiti, Dilip K.
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p. 24544 - 24550
(2014/07/07)
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- Iron(III)triflate as a highly efficient, recyclable and green catalyst for the N-Boc protection of amines
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Iron (III) triflate was used as an efficient catalyst for N-t-butoxycarbonylation of amines with di-t-butyl dicarbonate under solvent-free conditions at room temperature. Various aliphatic, aromatic, heterocyclic amines and aminols were protected as their corresponding mono-carbamates in excellent yields and short reaction times. Only two of the 23 monocarbamates were new. No competitive side reactions such as isocyanate, urea, nor N,N-di-Boc formation were observed. The reported method is mild and has the advantages of low cost, chemoselectivity and, because no solvent is used and the catalyst can be recycled, it is classifiable as a green procedure.
- Feng, Chengliang,Chu, Ningning,Zhang, Shuguang,Cai, Jin,Chen, Junqing,Hu, Huayou,Ji, Min
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p. 757 - 760
(2014/01/23)
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- BASE GENERATOR
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The present invention provides a base generator having the structure of formula (1): wherein R1, R2, R3, R4, R5, and Y{circle around (?)} are defined as in the specification. The base generator of the present invention can be used for imidization of a polyimide precursor, promoting crosslinking of epoxy monomers, or crosslinking of polyurethane or polyurea.
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Paragraph 0053; 0054
(2013/07/19)
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- Solvent free N-Boc protection of amines using amberlystr a 21 solid base resin as a reusable heterogeneous catalyst
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An efficient, environmentally benign, highly facile and convenient synthetic protocol for the selective t-butyl carboxylation of aliphatic, aromatic and heterocyclic amines using AmberlystR A 21 catalyst; a mild basic solid resin under solvent free conditions is reported. This method explores several advantages such as reusability of the heterogeneous catalyst, cleaner reaction profile, mild and solvent free system, short reaction time, operational simplicity, high conversions , excellent product yields and low cost of the catalyst. Furthermore since the catalyst is mild basic, decomposition of the carbamate formed is not observed if the reaction is continued for prolonged time as in the case of Lewis acid catalyzed N-Boc protection. This makes the present protocol a useful and attractive for N-Boc protection of amines.
- Tekale, Sunil U.,Kauthale, Sushama S.,Pawar, Rajendra P.
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p. 1619 - 1623
(2013/09/12)
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- 1,3-Disulfonic acid imidazolium hydrogen sulfate as an efficient and reusable ionic liquid catalyst for the N-Boc protection of amines
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1,3-Disulfonic acid imidazolium hydrogen sulfate is easily prepared and used as an efficient and recyclable ionic liquid for the N-Boc protection of amines at room temperature and neat conditions. This new method consistently has the advantages of excellent yields and short reaction times. Further, the catalyst can be reused and recovered for several times without loss of activity.
- Shirini, Farhad,Khaligh, Nader Ghaffari
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p. 386 - 393
(2013/03/14)
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- N-sulfonic acid poly(4-vinylpyridinium) chloride: An efficient and reusable solid acid catalyst in N-Boc protection of amines
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N-sulfonic acid poly(4-vinylpyridinium) chloride is easily prepared by the reaction of poly(4-vinylpyridine) with neat chlorosulfonic acid. This reagent can be used as an efficient catalyst for the N-Boc protection of amines at room temperature and neat conditions. This new method consistently has the advantages of excellent yields and short reaction times. Further, the catalyst can be reused and recovered for several times.
- Shirini, Farhad,Khaligh, Nader Ghaffari,Jolodar, Omid Goli
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p. 181 - 188
(2013/07/26)
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- {[[K.18-Crown-6]Br3}n: A tribromide catalyst for the catalytic protection of amines and alcohols
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{[K.18-Crown-6]Br3}n, a unique tribromide-type catalyst, was utilized for the N-boc protection of amines and trimethylsilylation (TMS) and tetrahydropyranylation (THP) of alcohols. The method is general for the preparation of N-boc derivatives of aliphatic (acyclic and cyclic) and aromatic, and primary and secondary amines and also various TMS-ethers and THP-ethers. The simple separation of the catalyst from the product is one of the many advantages of this method.
- Chehardoli, Gholamabbas,Zolfigol, Mohammad Ali,Derakhshanpanah, Fateme
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p. 1730 - 1733
(2013/10/21)
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- Synthesis and thermal studies of aliphatic polyurethane dendrimers: A geometric approach to the Flory-Fox equation for dendrimer glass transition temperature
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A new convergent synthesis for polyurethane dendrons to generation 4, and dendrimers to generation 3, is presented with control of surface functionality. The systematic synthesis of twenty-six new dendritic materials has led to a study of the factors affecting Tg using widely accepted approaches. The established understanding of dendritic polymer Tg behaviour is that the Flory-Fox models, used for linear polymers, are unsuitable as the high number of chain ends and globular nature of dendrimers requires special consideration. In our review of the accepted understanding we have shown that the conventional Flory-Fox models predict Tg∞ accurately and generate identical values to the established modifications of the Flory-Fox equation that consider 'dendrimer-relevant' aspects such as the non-zero values of ne/M at infinite molecular weight. We also present a new approach using the geometric parameters of dendrimer mass evolution suggesting that the Flory-Fox equation is indeed appropriate for determination of dendrimer T g∞.
- Stoddart, Alison,Feast, W. James,Rannard, Steve P.
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experimental part
p. 1096 - 1108
(2012/05/21)
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- CDI-mediated monoacylation of symmetrical diamines and selective acylation of primary amines of unsymmetrical diamines
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A highly efficient and green protocol for monoacylation of symmetrical diamines and chemoselective acylation of primary amines of unsymmetrical diamines has been developed.
- Verma, Sanjeev K.,Ghorpade, Ramarao,Pratap, Ajay,Kaushik
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experimental part
p. 326 - 329
(2012/04/10)
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- Solvent free, N,N'-carbonyldiimidazole (CDI) mediated amidation
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The method involves CDI mediated amidation under solvent-free conditions. The protocol is green, simple, and scalable and has broad structural applicability. The protocol has also been used for BOC protection of amine. The protocol has reduced the time for CDI mediated amidation from 2-4 h to 5-10 min without the use of any dry organic solvent and nitrogen atmosphere.
- Verma, Sanjeev K.,Ghorpade, Ramarao,Pratap, Ajay,Kaushik
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experimental part
p. 2373 - 2376
(2012/05/31)
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- Poly(4-vinylpyridine) catalyzed chemoselective O-TMS protection of alcohols and phenols and N-Boc protection of amines
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Poly(4-vinylpyridine) (PVP) acts as an efficient and reusable catalyst for the selective and efficient trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) and N-tert-butoxycarbonylation of amines with (Boc)2O. All reactions were performed under mild conditions in good to high yields. Iranian Chemical Society 2012.
- Shirini, Farhad,Khaligh, Nader Ghaffari
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p. 495 - 502
(2013/02/22)
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- Succinimide sulfonic acid (SuSA): An efficient and recyclable catalyst for the chemoselective N-Boc protection of amines
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Succinimide sulfonic acid (SuSA) as a stable reagent is easily prepared by the reaction of succinimide with neat chlorosulfonic acid. This compound is able to catalyze the chemoselective conversion of amines to their corresponding N-Boc protected derivatives with (Boc)2O. All reactions were performed under mild conditions, giving the desired products in good to high yields. Springer-Verlag 2011.
- Shirini, Farhad,Khaligh, Nader Ghaffari
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experimental part
p. 631 - 635
(2012/07/03)
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- Simple and efficient method for n-boc protection of amines using PEG-400 as a reaction medium under mild conditions
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Simple and efficient method for N-Boc protection of amines using PEG-400 as an ecofriendly reaction medium at room temperature is described. Various aromatic, heteroaromatic, and aliphatic amines were converted to the corresponding N-tert-butyl-carbamates in good to excellent yields in short times.
- Zeng, Hongyao,Li, Yongjia,Shao, Huawu
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experimental part
p. 25 - 32
(2011/10/19)
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- Guanidine hydrochloride as an organocatalyst for N-Boc protection of amino groups
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A simple and efficient method for the chemoselective N-Boc protection of the amine moiety in a variety of compounds is described using di-tert-butyl dicarbonate and guanidine hydrochloride as an organocatalyst in ethanol at 35-40°C. Selective mono-N-Boc protection of diamines and chemoselective protection of hydroxylamines without formation of any side products is achieved. Amino acids and peptides are N-Boc protected efficiently in excellent yields under convenient reaction conditions.
- Jahani, Fatemeh,Tajbakhsh, Mahmood,Golchoubian, Hamid,Khaksar, Samad
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supporting information; experimental part
p. 1260 - 1264
(2011/04/15)
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- An efficient and highly chemoselective N-Boc protection of amines, amino acids, and peptides under heterogeneous conditions
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A simple and efficient procedure for chemoselective mono-N-Boc protection of various structurally diverse amines, amino acids, and peptides with di-tert-butyl dicarbonate using Amberlyst-15 as catalyst in ethanol is described. The catalyst can be readily separated from the reaction products with simple filtration and recovered for direct reuse. No competitive side-reactions such as formation of isocyanate, urea, oxazolidinone, and N,N-di-Boc derivatives were observed.
- Jahani, Fatemeh,Tajbakhsh, Mahmood,Khaksar, Samad,Azizi, Mohamad Reza
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experimental part
p. 1035 - 1043
(2012/07/27)
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- ZnO nanorods as an efficient and heterogeneous catalyst for N-Boc protection of amines and amine derivatives
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An efficient ZnO nano catalyst, which was readily prepared from Zn(CH3CO2)2, 2H2O and PVP by a chemical solution approach has successfully catalyzed N-tertbutoxy carbonylation of amines. The ZnO nanorods were successful and gave promising results for highly active and chemoselective as well as easily recyclable catalyst for the NBoc protection reaction of a wide variety of amines. The catalyst could be easily recycled for five times without noticeable decrease in catalytic activity. The ZnO nanocatalyst was characterized with XRD and SEM.
- Nouria, Azita,Akbari, Jafar,Heydaric, Akbar,Nouri, Arezu
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experimental part
p. 38 - 42
(2012/05/04)
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- Synthesis and crystal structure determination of [H2-cryptand 222](Br3)2: A unique tribromide catalyst for the catalytic chemoselective N-boc protection of amines
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The organic tribromide, [H2-cryptand 222](Br3) 2 was synthesized and characterized by X-ray crystallography, and was utilized as an active catalyst for the N-boc protection of amines. The method is general for the preparation of N-boc derivatives of aliphatic (acyclic and cyclic), aromatic, primary and secondary amines. We also applied our new reaction protocols for the N-boc protection of some new amines and spectral and physical data for the obtained products are reported.
- Chehardoli, Gholamabbas,Zolfigol, Mohammad Ali,Khakyzadeh, Vahid,Golbedaghi, Reza,Hall, Nikita A.,Blackman, Allan G.
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experimental part
p. 538 - 543
(2012/01/03)
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- Protic ionic liquid [TMG][Ac] as an efficient, homogeneous and recyclable catalyst for Boc protection of amines
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An efficient and practical protocol for the chemoselective N-Boc protection of various structurally different aryl, aliphatic and heterocyclic amines was carried out with (Boc)2O using protic 1, 1, 3, 3-tetra-methylguanidinium acetate (10 mol%) as recyclable catalyst under solvent free condition at ambient temperature. No competitive side reactions (isocyanate, urea and N, N-di-Boc) were observed. α-Amino alcohols afforded the N-Boc-derivative without oxazolidinone formation.
- Akbari, Jafar,Heydari, Akbar,Ma'mani, Leila,Hassan Hosseini, Seyed
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experimental part
p. 544 - 547
(2010/11/05)
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- Ethynyl-1,2-benziodoxol-3(1H)-one (EBX): An exceptional reagent for the ethynylation of keto, cyano, and nitro esters
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Hot alkyne! The in situ generation of ethynyl-1,2-benziodoxol-3(1H)-one (EBX) from a silyl-protected reagent by using TBAF is reported. EBX displayed exceptional acetylene transfer ability onto stabilized enolates (see scheme), even at -78 □°C. The mild reaction conditions allowed the first ethynylation reactions of linear keto, cyano, and nitro esters in high yields to give all-carbon quaternary centers or non-natural amino acids after selective reduction of the nitro group.
- Gonzalez, Davinia Fernandez,Brand, Jonathan P.,Waser, Jerome
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supporting information; experimental part
p. 9457 - 9461
(2010/10/03)
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- Susceptibility of methyl 3-Amino-1H-pyrazole-5-carboxylate to acylation
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In the search for a new method of synthesis of hybrid peptides with aminopyrazole carboxylic acid, we tried to force selective acylation at the aromatic amino group instead of at the ring nitrogen atom with fairly gentle acylating agents. The acylating agents used were acid anhydrides: acetic anhydride, tert-butyl pyrocarbonate, and 2-(2-methoxyethoxy)ethoxyacetic acid/dicyclohexylcarbodiimide. We succceded in acylation at this amino group with almost none at the ring nitrogen atom. Sometimes, however, acylation in small quantities at the ring nitrogen atom was observed as a by-product. To remove this by-product, imidazole was used. Thus, we were able to obtain the hybrid peptides in question with no protection and subsequent removal required. We synthesized a few these free peptides with no protection of the pyrazole ring. This is a simpler method than that being used currently.
- Kusakiewicz-Dawid, Anna,Gorecki, Lukasz,Masiukiewicz, Elzbieta,Rzeszotarska, Barbara
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experimental part
p. 4122 - 4132
(2009/12/24)
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- An efficient and chemoselective Br?nsted acidic ionic liquid-catalyzed N-Boc protection of amines
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The first report of a Br?nsted acidic ionic liquid, 1-methylimidazolium tetrafluoroborate [(HMIm)BF4], catalyzed efficient and chemoselective N-Boc protection of various amines using (Boc)2O is presented. Optically pure amino alcohols and amino acid esters were converted efficiently to their corresponding optically pure N-Boc derivatives. The reported method is mild, solvent-free and has the advantages of both homogeneous and heterogeneous catalysis with high product yields, selectivity and ease of product separation.
- Sunitha, Sadula,Kanjilal, Sanjit,Reddy, P. Srinivasa,Prasad, Rachapudi B.N.
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p. 2527 - 2532
(2008/09/19)
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- Hydrogen bond catalyzed chemoselective N-tert-butoxycarbonylation of amines
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A novel, chemoselective mono-N-Boc protection of various structurally diverse amines with di-tert-butoxypyrocarbonate (Boc)2O is described that relies on selective carbonyl activation by hydrogen bond formation. This mild, acid- and metal-free process requires only catalytic amounts of thiourea as hydrogen bond donor.
- Khaksar, Samad,Heydari, Akbar,Tajbakhsh, Mahmood,Vahdat, Seyed Mohammad
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p. 3527 - 3529
(2008/09/21)
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- 1,1,1,3,3,3-Hexafluoroisopropanol: A recyclable organocatalyst for N-Boc protection of amines
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A simple and efficient protocol for the chemoselective mono-N-Boc protection of various structurally diverse amines with di-tert-butyl dicarbonate using 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) as solvent and catalyst is described. The catalyst can be readily separated from the reaction products and recovered for direct reuse. No competitive side reactions such as formation of isocyanate, urea, and N,N-di-Boc were observed. α-Amino alcohols afforded the N-Boc derivatives without oxazolidinone formation. Georg Thieme Verlag Stuttgart.
- Heydari, Akbar,Khaksar, Samad,Tajbakhsh, Mahmood
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experimental part
p. 3126 - 3130
(2009/04/06)
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- Environmentally benign N-Boc protection under solvent- and catalyst-free conditions
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A practical and highly efficient method for the protection of amines to their corresponding N-Boc derivatives is reported. In the absence of any solvent and catalyst, the present strategy works well for a series of electron-deficient and electron-rich aromatic amines as well as some sterically hindered substrates. Georg Thieme Verlag Stuttgart.
- Jia, Xueshun,Huang, Qing,Li, Jian,Li, Shaoyu,Yang, Qiushi
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p. 806 - 808
(2007/12/26)
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- N-tert-Butoxycarbonylation of amines using H3PW12O40 as an efficient heterogeneous and recyclable catalyst
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The commercially available heteropoly acid H3PW12O40 (0.5 mol %) is a very efficient and environmentally benign catalyst for N-tert-butoxycarbonylation of amines (primary, secondary) with di-tert-butyl dicarbonate at room temperature in short reaction times (10 min). No competitive side products such as isocyanates, ureas, N,N-di-tert-butoxycarbonyls, O-Boc and oxazolidinones were observed. Chiral α-amino alcohols and esters afforded the corresponding N-Boc derivatives chemoselectively in excellent yields.
- Heydari, Akbar,Shiroodi, Roohollah Kazem,Hamadi, Hossein,Esfandyari, Maryam,Pourayoubi, Mehrdad
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p. 5865 - 5868
(2008/02/09)
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- Molecular iodine-catalyzed facile procedure for N-Boc protection of amines
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An efficient and practical protocol for the protection of various structurally and electronically divergent aryl and aliphatic amines using (Boc)2O in the presence of a catalytic amount of molecular iodine (10 mol%) under solvent-free conditions at ambient temperature is presented.
- Varala, Ravi,Nuvula, Sreelatha,Adapa, Srinivas R.
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p. 8283 - 8286
(2007/10/03)
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- N-boc protection of amines with di-tert-butyldicarbonate in water under neutral conditions in the presence of β-cyclodextrin
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A new protocol for protection of aryl and aliphatic amines was developed with (Boc)2O in the presence of β-cyclodextrin in water. A catalytic amount of β-cyclodextrin is specific for activation of amines. This procedure works well on a wide variety of both electron-rich and electron-deficient amines. Georg Thieme Verlag Stuttgart.
- Somi Reddy,Narender,Nageswar,Rama Rao
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p. 1110 - 1112
(2007/10/03)
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- Synthesis of polyamine compounds
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This invention relates to methods of preparing the compounds of formula (V): Each variable in this formula is defined in the specification.
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Page/Page column 9-10
(2008/06/13)
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- Stereoselective glycosylation of exo-glycals by microwave-assisted Ferrier rearrangement
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exo-Glycosyl carbonates were shown to be efficient glycosyl donors in microwave-assisted glycosylation. In these reactions α-glycosyl additions occurred with excellent stereoselectivity and were complete in 4-8 min with 75-92% yield. Interestingly exo-glycals were found to have higher activity than endo-glycals and common glycosides, the reactions of which can be improved by the addition of Lewis acid to result in a higher yield and enhanced stereoselectivity.
- Lin, Hui-Chang,Chang, Chih-Chun,Chen, Jia-Yi,Lin, Chun-Hung
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p. 297 - 301
(2007/10/03)
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- Lithium perchlorate-catalyzed Boc protection of amines and amine derivatives
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A new mild and chemoselective method for mono-N-protection of amines and amine derivatives as tert-butoxycarbonyl derivatives is reported. The reaction proceeds with lithium perchlorate (20 mol %) and pyrocarbonates, and shows general applicability. The catalytic action of LiClO4 is specific for the activation of Boc2O, thus acid-sensitive functionalities of the starting materials remain unchanged in the protection process. This procedure works well for sterically hindered primary amine as well as electron-deficient primary arylamines, primary and secondary amino alcohols, α-amino acid esters, hydroxylamines, hydrazines and sulfonamides.
- Heydari, Akbar,Hosseini, Seyed Esmaeil
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p. 1929 - 1932
(2007/10/03)
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- Rapid and facile Lewis acid catalysed Boc protection of amines
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Efficient Boc protection of amines using (Boc)2O in the presence of a catalytic amount of ZrCl4 (10 mol %) in acetonitrile at room temperature is reported with short reaction times and high yields. Efficient Boc protection of amines was carried out using (Boc)2O in the presence of a catalytic amount of ZrCl4 (10 mol %) in acetonitrile at room temperature. The reaction times are very short and the yields are generally high.
- Sharma,Janardhan Reddy,Sree Lakshmi,Radha Krishna, Palakodety
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p. 6963 - 6965
(2007/10/03)
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- Selective convergent synthesis of aliphatic polyurethane dendrimers
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An overview is given of the first convergent synthesis of aliphatic polyurethane homodendrimers. The synthesis only uses urethane links and has a repeating structure that is consistent from the surface groups through to the core nitrogen atom. Dendrimer molecules up to the third generation and dendrons up to the fourth generation have been synthesized with masses over 7000 Da.
- Feast, W. James,Rannard, Steve P.,Stoddart, Alison
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p. 9704 - 9706
(2007/10/03)
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