- Sustainable Route Toward N-Boc Amines: AuCl3/CuI-Catalyzed N-tert-butyloxycarbonylation of Amines at Room Temperature
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N-tert-butoxycarbonyl (N-Boc) amines are useful intermediates in synthetic/medicinal chemistry. Traditionally, they are prepared via an indirect phosgene route with poor atom economy. Herein, a step- and atom-economic synthesis of N-Boc amines from amines, t-butanol, and CO was reported at room temperature. Notably, this N-tert-butyloxycarbonylation procedure utilized ready-made substrates, commercially available AuCl3/CuI as catalysts, and O2 from air as the sole oxidant. This catalytic system provided unique selectivity for N-Boc amines in good yields. More significantly, gram-scale preparation of medicinally important N-Boc amine intermediates was successfully implement, which demonstrated a potential application prospect in industrial syntheses. Furthermore, this approach also showed good compatibility with tertiary and other useful alcohols. Investigations of the mechanisms revealed that gold catalyzed the reaction and copper acted as electron transfer mediator in the catalytic cycle.
- Cao, Yanwei,He, Lin,Huang, Yang
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- Photoredox catalysis on unactivated substrates with strongly reducing iridium photosensitizers
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Photoredox catalysis has emerged as a powerful strategy in synthetic organic chemistry, but substrates that are difficult to reduce either require complex reaction conditions or are not amenable at all to photoredox transformations. In this work, we show that strong bis-cyclometalated iridium photoreductants with electron-rich β-diketiminate (NacNac) ancillary ligands enable high-yielding photoredox transformations of challenging substrates with very simple reaction conditions that require only a single sacrificial reagent. Using blue or green visible-light activation we demonstrate a variety of reactions, which include hydrodehalogenation, cyclization, intramolecular radical addition, and prenylationviaradical-mediated pathways, with optimized conditions that only require the photocatalyst and a sacrificial reductant/hydrogen atom donor. Many of these reactions involve organobromide and organochloride substrates which in the past have had limited utility in photoredox catalysis. This work paves the way for the continued expansion of the substrate scope in photoredox catalysis.
- Shon, Jong-Hwa,Kim, Dooyoung,Rathnayake, Manjula D.,Sittel, Steven,Weaver, Jimmie,Teets, Thomas S.
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p. 4069 - 4078
(2021/04/06)
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- Cobalt-Catalyzed C(sp2)-C(sp3) Suzuki-Miyaura Cross Coupling
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A cobalt-catalyzed method for the C(sp2)-C(sp3) Suzuki-Miyaura cross coupling of aryl boronic esters and alkyl bromides is described. Cobalt-ligand combinations were assayed with high-throughput experimentation, and cobalt(II) sources with trans-N,N′-dimethylcyclohexane-1,2-diamine (DMCyDA, L1) produced optimal yield and selectivity. The scope of this transformation encompassed steric and electronic diversity on the aryl boronate nucleophile as well as various levels of branching and synthetically valuable functionality on the electrophile. Radical trap experiments support the formation of electrophile-derived radicals during catalysis.
- Ludwig, Jacob R.,Simmons, Eric M.,Wisniewski, Steven R.,Chirik, Paul J.
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supporting information
(2020/11/02)
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- Desulfonylative Arylation of Redox-Active Alkyl Sulfones with Aryl Bromides
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We describe the development of the first reductive cross-electrophile coupling between alkyl sulfones and aryl bromides. The use of alkyl sulfones offers strategic advantages over other alkyl electrophiles as they can be incorporated into molecules in unique ways and permit α-functionalization prior to coupling. The conditions developed here enable incorporation of a wide array of aromatic rings onto (fluoro)alkyl scaffolds with broad functional group tolerance and generality, making this a practical method for late-stage diversification.
- Hughes, Jonathan M. E.,Fier, Patrick S.
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p. 5650 - 5654
(2019/08/01)
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- A Simple, efficient, Catalyst-Free and Solvent-Less Microwave-Assisted process for N-Cbz Protection of Several amines
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A simple, green and chemo-selective method for the N-benzyloxycarbonylation of amines, β-amino alcohols, α-amino esters and sulfonamides has been developed under microwave irradiation. Good to excellent yields of the N-benzyloxy-carbamates compounds were obtained in short times without any side products.
- Aouf, Zineb,Mansouri, Rachida,Lakrout, Salah,Berredjem, Malika,Aouf, Nour-Eddine
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p. 151 - 156
(2017/08/02)
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- Orthoester in Cyclodehydration of Carbamate-Protected Amino Alcohols under Acidic Conditions
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The first acid-promoted reaction system to form azaheterocycles from N -carbamate-protected amino alcohols is described. The reaction involves the activation of the hydroxyl group via the use of orthoesters. Despite the reduced nucleophilicity of carbamate nitrogen, this reaction system provides several types of pyrrolidines and piperidines in good to high yields. Using this protocol, prolinol derivatives can also be synthesized from carbamate-protected amino diols with regio- and stereoselectivity.
- Park, Heemin,Kwon, Yongseok,Shin, Jae Eui,Kim, Woo-Jung,Hwang, Soonho,Lee, Seokwoo,Kim, Sanghee
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p. 2761 - 2767
(2017/06/13)
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- Light-Mediated Reductive Debromination of Unactivated Alkyl and Aryl Bromides
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Cleavage of carbon-halogen bonds via either single-electron reduction or atom transfer is a powerful transformation in the construction of complex molecules. In particular, mild, selective hydrodehalogenations provide an excellent follow-up to the application of halogen atoms as directing groups or the utilization of atom transfer radical addition (ATRA) chemistry for the production of hydrocarbons. Here we combine the mechanistic properties of photoredox catalysis and silane-mediated atom transfer chemistry to accomplish the hydrodebromination of carbon-bromide bonds. The resulting method is performed under visible light irradiation in an open vessel and is capable of the efficient reduction of a variety of unactivated alkyl and aryl substrates.
- Devery, James J.,Nguyen, John D.,Dai, Chunhui,Stephenson, Corey R. J.
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p. 5962 - 5967
(2016/09/09)
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- Cis-Trans Conformational Analysis of δ-Azaproline in Peptides
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The cis-trans isomerization and conformer specificity of δ-azaproline and its carbamate-protected form in linear and cyclic peptides were investigated using NMR and α-chymotrypsin assay. Comparisons of the chemical shift value of the α-hydrogen in each case of δ-azaproline-containing peptides with conformer-specific locked diketopiperazines reveal the fact that an upfield chemical shift value corresponds to cis conformer and a downfield value corresponds to a trans conformer. δ-Azaproline adopts cis-conformation in simple amides, dipeptides, and tripeptides whereas its carbamate-protected form adopts trans-conformation. In the case of longer, linear or cyclic peptides, vice versa results are obtained. Interestingly, in all these peptides exclusively one conformer, either cis or trans, is stabilized. This cis-trans isomerization is independent of both temperature and solvents; only the δ-nitrogen protecting group plays key role in the isomerization. δ-Azaproline is conformer-specific in either of its protected or deprotected forms, which is a unique property of this proline. Unlike other covalently modified proline surrogates, this isomerization of δ-azaproline can be tuned easily by a protecting group. The mechanism of cis-trans isomerization of δ-azaproline during deprotection and reprotection is supported by theoretical calculations.
- Duttagupta, Indranil,Misra, Debojyoti,Bhunya, Sourav,Paul, Ankan,Sinha, Surajit
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p. 10585 - 10604
(2015/11/18)
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- Hydrodecarboxylation of Carboxylic and Malonic Acid Derivatives via Organic Photoredox Catalysis: Substrate Scope and Mechanistic Insight
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A direct, catalytic hydrodecarboxylation of primary, secondary, and tertiary carboxylic acids is reported. The catalytic system consists of a Fukuzumi acridinium photooxidant with phenyldisulfide acting as a redox-active cocatalyst. Substoichiometric quantities of Hünigs base are used to reveal the carboxylate. Use of trifluoroethanol as a solvent allowed for significant improvements in substrate compatibilities, as the method reported is not limited to carboxylic acids bearing α heteroatoms or phenyl substitution. This method has been applied to the direct double decarboxylation of malonic acid derivatives, which allows for the convenient use of dimethyl malonate as a methylene synthon. Kinetic analysis of the reaction is presented showing a lack of a kinetic isotope effect when generating deuterothiophenol in situ as a hydrogen atom donor. Further kinetic analysis demonstrated first-order kinetics with respect to the carboxylate, while the reaction is zero-order in acridinium catalyst, consistent with another finding suggesting the reaction is light limiting and carboxylate oxidation is likely turnover limiting. Stern-Volmer analysis was carried out in order to determine the efficiency for the carboxylates to quench the acridinium excited state.
- Griffin, Jeremy D.,Zeller, Mary A.,Nicewicz, David A.
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supporting information
p. 11340 - 11348
(2015/09/21)
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- N-Urethane protection of amines and amino acids in an ionic liquid
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An efficient, solvent-free protocol for the N-fluorenylmethoxycarbonylation and N-benzyloxycarbonylation of amines is described. The reaction of aliphatic and aromatic amines with FmocOSu and Cbz-Osu in [Bmim][BF4] at room temperature afforded the corresponding N-urethane derivatives in excellent yields and do not require any further purification. The method has been extended to the N-Fmoc and N-Cbz protection of amino acids. Absence of bases, very short reaction times, high yields, selectivity and ease of product separation are some advantages of this protocol.
- Di Gioia,Gagliardi,Leggio,Leotta,Romio,Liguori
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p. 63407 - 63420
(2015/08/11)
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- Nickel-catalyzed reductive cyclization of alkyl dihalides
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The reductive coupling protocol to intramolecular cyclization of dihaloalkanes is presented. It leads to five- and six-membered rings, with the former being more efficient. The incorporation of secondary alkyl halides generally promotes coupling efficiency. To the best of our knowledge, this is the first catalytic ring-closure reaction arising from dihaloalkanes under chemical reductive conditions.
- Xue, Weichao,Xu, Hailiang,Liang, Zhuye,Qian, Qun,Gong, Hegui
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p. 4984 - 4987
(2014/12/11)
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- Palladium-catalyzed intermolecular Heck reaction of alkyl halides
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Intermolecular Heck reaction of common alkyl halides, a longstanding problem in palladium catalysis, is realized with a simple Pd/dppf catalyst. Both primary and secondary alkyl halides are suitable for coupling with aromatic olefins. Single electron transfer from (dppf)Pd0 to alkyl halide initiated the catalytic cycle and gave alkyl radicals. This journal is the Partner Organisations 2014.
- Zou, Yinjun,Zhou, Jianrong
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supporting information
p. 3725 - 3728
(2014/04/03)
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- Aminolysis of benzyl 2-pyridyl thionocarbonate and t-butyl 2-pyridyl thionocarbonate: Effects of nonleaving groups on reactivity and reaction mechanism
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A kinetic study is reported for nucleophilic substitution reactions of benzyl 2-pyridyl thionocarbonate (5b) and t-butyl 2-pyridyl thionocarbonate (6b) with a series of alicyclic secondary amines in H2O at 25.0 °C. Generalbase catalysis, which has often been reported to occur for aminolysis of esters possessing a C=S electrophilic center, is absent for the reactions of 5b and 6b. The Bronsted-type plots for the reactions of 5b and 6b are linear with ssnuc = 0.29 and 0.43, respectively, indicating that the reactions of 5b proceed through a stepwise mechanism with formation of a zwitterionic tetrahedral intermediate (T±) being the rate-determining step while those of 6b proceed through a concerted mechanism. The reactivity of 5b and 6b is similar to that of their oxygen analogues (i.e., benzyl 2-pyridyl carbonate 5a and t-butyl 2-pyridyl carbonate 6a, respectively), indicating that the effect of modification of the electrophilic center from C=O to C=S (i.e., from 5a to 5b and from 6a to 6b) on reactivity is insignificant. In contrast, 6b is much less reactive than 5b, indicating that the replacement of the PhCH2 in 5b by the t-Bu in 6b results in a significant decrease in reactivity as well as a change in the reaction mechanism (i.e., from a stepwise mechanism to a concerted pathway). It has been concluded that the contrasting reactivity and reaction mechanism for the reactions of 5b and 6b are not due to the electronic effects of PhCH2 and t-Bu but are caused by the large steric hindrance exerted by the bulky t-Bu in 6b.
- Kim, Min-Young,Lee, Jae-In,Um, Ik-Hwan
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p. 1115 - 1119
(2013/07/28)
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- Aminolysis of benzyl 4-pyridyl carbonate in acetonitrile: Effect of modification of leaving group from 2-pyridyloxide to 4-pyridyloxide on reactivity and reaction mechanism
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A kinetic study is reported for nucleophilic substitution reactions of benzyl 4-pyridyl carbonate 6 with a series of alicyclic secondary amines in MeCN. The plot of pseudo-first-order rate constant (kobsd) vs. [amine] curves upward, which is typical for reactions reported previously to proceed through a stepwise mechanism with two intermediates (i.e., a zwitterionic tetrahedral intermediate T± and its deprotonated form T-). Dissection of kobsd into the second-and third-order rate constants (i.e., Kk2 and Kk3, respectively) reveals that Kk3 is significantly larger than Kk2, indicating that the reactions proceed mainly through the deprotonation pathway (i.e., the k3 process) in a high [amine] region. This contrasts to the recent report that the corresponding aminolysis of benzyl 2-pyridyl carbonate 5 proceeds through a forced concerted mechanism. An intramolecular H-bonding interaction was suggested to force the reactions of 5 to proceed through a concerted mechanism, since it could accelerate the rate of leaving-group expulsion (i.e., an increase in k2). However, such H-bonding interaction, which could increase k2, is structurally impossible for the reactions of 6. Thus, presence or absence of an intramolecular H-bonding interaction has been suggested to be responsible for the contrasting reaction mechanisms (i.e., a forced concerted mechanism for the reaction of 5 vs. a stepwise mechanism with T± and T-as intermediates for that of 6).
- Bae, Ae Ri,Um, Ik-Hwan
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p. 2719 - 2723
(2012/11/07)
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- Kinetics and reaction mechanism of aminolyses of benzyl 2-pyridyl carbonate and t-butyl 2-pyridyl carbonate in acetonitrile
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Second-order rate constants (kN) have been measured spectrophotometrically for the reactions of benzyl 2- pyridyl carbonate 3 and t-butyl 2-pyridyl carbonate 4 with a series of alicyclic secondary amines in MeCN at 25.0 ± 0.1 ° C. Substrate 4 is much less reactive than 3 and the steric hindrance exerted by the bulky t-Bu group in 4 has been attributed to its decreased reactivity. The Bronsted-type plots for the reactions of 3 and 4 are linear with ssnuc = 0.57 and 0.45, respectively. Thus, the reactions have been concluded to proceed through a concerted mechanism, although the current reactions were expected to proceed through a stepwise mechanism with a zwitterionic tetrahedral intermediate T±. It has been proposed that the rate of leaving-group expulsion is accelerated by the intramolecular H-bonding interaction in T± and the "push" provided by the RO group through the resonance interaction. Thus, the enhanced nucleofugality forces the reactions to proceed through a concerted mechanism. The reactivity-selectivity principle (RSP) is not applicable to the current reaction systems, since the reaction of the less reactive 4 results in a smaller ssnuc than that of the more reactive 3. Steric hindrance exerted by the bulky t-Bu group in 4 has been suggested to be responsible for the failure of the RSP. Copyright
- Bae, Ae Ri,Um, Ik-Hwan
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scheme or table
p. 1547 - 1550
(2012/07/28)
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- Amberlyst-15 catalyzed Cbz protection of amines under solvent-free conditions
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Amberlyst-15 can effectively catalyze Cbz protection of aliphatic and aromatic amines within 10-15 min under solvent-free conditions. The catalyst can be used repeatedly without loss of activity, and the reaction requires no workup and gives excellent yields. Taylor & Francis Group, LLC.
- Bora, Pranja P.,Vanlaldinpuia, Khiangte,Rokhum, Lalthazuala,Bez, Ghanashyam
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experimental part
p. 2674 - 2683
(2011/08/22)
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- Bromodimethyl sulfonium bromide mediated rapid and facile protection of amines
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A new clean protocol for protection of aryl and aliphatic amines with t-butoxycarbonyl (t-BOC) and benzyloxycarbonyl (Cbz) catalyzed by simple (bromodimethyl) sulfonium bromide has been developed. Rapid protection of amines in excellent yields in totally solvent-free conditions has been achieved. Copyright
- Shailaja,Manjula,Vittal Rao
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experimental part
p. 2073 - 2080
(2011/07/31)
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- Cobalt-catalyzed reductive allylation of alkyl halides with allylic acetates or carbonates
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An efficient method for the direct allylation of alkyl halides catalyzed by simple cobalt(II) bromide has been developed. This reaction, using a variety of substituted allylic acetates or carbonates, provides the linear product as the major product. It displays broad substrate scope and good functional group tolerance. Copyright
- Qian, Xin,Auffrant, Audrey,Felouat, Abdellah,Gosmini, Corinne
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supporting information; experimental part
p. 10402 - 10405
(2011/12/03)
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- An excellent method for Cbz-protection of amines
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Cbz-protection of aliphatic and aromatic amines can be accomplished with benzylchloroformate using a catalytic amount of dodecatungstophosphoric acid hydrate (0.05 equiv). The reaction is simple, fast, does not require aqueous work-up and gives excellent yields.
- Vanlaldinpuia, Khiangte,Sema, H. Atoholi,Rokhum, Lalthazuala,Bez, Ghanashyam
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experimental part
p. 228 - 229
(2010/08/20)
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- A catalyst-free N-benzyloxycarbonylation of amines in aqueous micellar media at room temperature
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N-Benzyloxycarbonylation of amines was carried out in aqueous micellar media. Aliphatic (open and cyclic), aromatic and heteroaromatic amines react with Cbz-Cl to give excellent yields of products. The reactions were carried out in water and at room temperature.
- Shrikhande, Janhavi J.,Gawande, Manoj B.,Jayaram, Radha V.
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p. 4799 - 4803
(2008/12/22)
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- An efficient and chemoselective Cbz-protection of amines using silica-sulfuric acid at room temperature
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A simple, facile, and chemoselective N-benzyloxycarbonylation of amines using silica-sulfuric acid that proceeds under solvent-free conditions at room temperature has been achieved. These reactions are applicable to a wide variety of primary (aliphatic and cyclic) secondary amines, amino alcohols, and heterocyclic amines.
- Gawande, Manoj B.,Polshettiwar, Vivek,Varma, Rajender S.,Jayaram, Radha V.
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p. 8170 - 8173
(2008/03/13)
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- Reactions of iminium ions with Michael acceptors through a Morita-Baylis-Hillman-type reaction: Enantiocontrol and applications in synthesis
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(Chemical Equation Presented) All adducts one way: Iminium ions, generated in situ from the corresponding N,O-acetals, can be used as electrophiles in a Morita-Baylis-Hillman-type reaction with a wide range of Michael acceptors (enones, enals, S- and O-acrylates). The reaction has been rendered asymmetric using sulfide 1 (see scheme; DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene, TMSOTf=trimethylsilyl trifluoromethanesulfonate).
- Myers, Eddie L.,De Vries, Johannes G.,Aggarwal, Varinder K.
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p. 1893 - 1896
(2008/03/12)
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- Iron-catalyzed cross-coupling of alkyl halides with alkenyl Grignard reagents
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(Chemical Equation Presented) Cheap and safe: An iron-catalyzed cross-coupling reaction between alkyl halides and alkenyl Grignard reagents is described. This C-C bond coupling reaction is promoted by the cheap and nontoxic FeCl3 and displays good tolerance against various functional groups.
- Guerinot, Amandine,Reymond, Sebastien,Cossy, Janine
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p. 6521 - 6524
(2008/09/16)
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- Photochemical protection of amines with Cbz and Fmoc groups
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The photochemical conversion of amines into carbamates was achieved using N-Cbz-, N-Fmoc-, and N-Boc-5,7-dinitroindolines. This reaction allows the protection of amines in neutral medium. Primary and unhindered secondary amines were protected to yield their benzyloxycarbonyl- and 9-fluorenylmethoxycarbonyl derivatives efficiently, whereas bulky amines or anilines gave low yields or no product. On the other hand, the formation of N-Boc compounds, although possible, proceeded only with low yields.
- Helgen, Celine,Bochet, Christian G.
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p. 2483 - 2486
(2007/10/03)
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- Benzyl 4,6-dimethoxy-1,3,5-triazinyl carbonate as N-protecting reagent
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A new active carbonate ester, benzyl 4,6-dimethoxy-1,3,5-triazinyl carbonate (Z-DMT), was prepared, and found to be a useful reagent for the introduction of benzyloxycarbonyl group into amines. Since Z-DMT is neither unstable nor irritating, it is practically useful.
- Hioki, Kazuhito,Fujiwara, Miho,Tani, Shohei,Kunishima, Munetaka
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- Efficient Cs2CO3-promoted solution and solid phase synthesis of carbonates and carbamates in the presence of TBAI
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Novel solution and solid-phase methods for the synthesis of carbonates and carbamates were developed using cesium bases and TBAI via a three-component coupling. Cesium carbonate not only promoted successful carbonylations of alcohols and carbamations of amines, but also suppressed common side reactions traditionally seen using existing protocols. Various alcohols and amines were examined, using a wide array of alkyl halides, and the results demonstrated this methodology was highly chemoselective. In particular, use of either sterically demanding substrates or amino acid derivatives afforded the corresponding products exclusively, offering a wide variety of applications such as novel protecting groups and peptidomimetic syntheses.
- Salvatore, Ralph N,Chu, Feixia,Nagle, Advait S,Kapxhiu, Elona A,Cross, Richard M,Jung, Kyung Woon
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p. 3329 - 3347
(2007/10/03)
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- THF-CONTAINING SULFONAMIDE INHIBITORS OF ASPARTYL PROTEASE
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The present invention relates to a class of THF-containing sulfonamides which are aspartyl protease inhibitors. This invention also relates to pharmaceutical compositions comprising these compounds. The compounds and pharmaceutical compositions of this invention are particularly well suited for inhibiting HIV-1 and HIV-2 protease activity and consequently, may be advantageously used as anti-viral agents against the HIV-1 and HIV-2 viruses. This invention also relates to methods for inhibiting the activity of HIV aspartyl protease using the compounds of this invention.
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- Biohydroxylations of Cbz-protected alkyl substituted piperidines by Beauveria bassiana ATCC 7159
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N-Benzyloxycarbonyl (Cbz) protected piperidines are hydroxylated with greater regioselectivity than the corresponding N-benzoyl analogues when incubated with the fungus Beauveria bassiana ATCC 7159. Cbz-protected piperidines 1-3, 5-7, have been biotransfo
- Aitken, Suzanne J.,Grogan, Gideon,Chow, Cathy S.-Y.,Turner, Nicholas J.,Flitsch, Sabine L.
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p. 3365 - 3370
(2007/10/03)
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- Convenient protection of amines as carbamates using polymer-bound HOBT as catalyst
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A method for the facile protection of primary and secondary amines as carbamate (Cbz, Fmoc and t-Boc) derivatives using polymer bound 1-hydroxybenzotriazole (HOBT) is reported.
- Dendrinos, Kleanthis G.,Kalivretenos, Aristotle G.
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p. 1463 - 1464
(2007/10/03)
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- ANTITHROMBOTIC AGENTS
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This invention relates to thrombin inhibiting compounds having the FormulaIX--Y--NH--(CH 2) r--G I where X, Y, r and G have the values defined in the description, as well as pharmaceutical formulations containing those compounds and methods of their use as thrombin inhibitors, coagulation inhibitors, and thromboembolic disorder agents.
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- ANTITHROMBOTIC AGENTS
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This invention relates to thrombin inhibiting compounds having the FormulaIX--Y--NH--(CH 2) r--G I where X, Y, r and G have the values defined in the description, as well as pharmaceutical formulations containing those compounds and methods of their use as thrombin inhibitors, coagulation inhibitors, and thromboembolic disorder agents.
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- ANTITHROMBOTIC AGENTS
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This invention relates to thrombin inhibiting compounds having the FormulaIX--Y--NH--(CH 2) r--G I where X, Y, r and G have the values defined in the description, as well as pharmaceutical formulations containing those compounds and methods of their use as thrombin inhibitors, coagulation inhibitors, and thromboembolic disorder agents.
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- Aryl substituted heterocycles
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The present invention concerns the novel use of aryl substituted heterocycles of formula I, set out below, which antagonize the pharmacological actions of one of ent endogenous neuropeptide tachykinins an the neurokinin 2 (NK2) receptor making them useful whenever such antagonism is desired, such as in the treatment of asthma and related conditions. The invention also provides pharmaceutical compositions containing the aryl substituted heterocycles for use in such treatment. Certain novel aryl substituted heterocycles of formula I and novel intermediates for their manufacture are also provided. STR1
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- Alkyl 1-Chloroalkyl Carbonates: Reagents for the Synthesis of Carbamates and Protection of Amino Groups
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The synthesis of 1-chloroalkyl carbonates and their reaction with various type of amines are described.This reaction is useful for the synthesis of carbamate pesticides and for the protection of various amino groups, including amino acids.
- Barcelo, Gerard,Senet, Jean-Pierre,Sennyey, Gerard,Bensoam, Jean,Loffet, Albert
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p. 627 - 632
(2007/10/02)
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- 3-Alkoxycarbonyl-2-oxazolones and Their Homopolymers as Highly Preservable Amino-Protecting Reagents. tert-Butoxy-carbonylation and Benzyloxycarbonylation of Amino Groups
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Highly preservable amino protecting reagents derived from the 2-oxazolone moiety as a common activating mediator have been developed. 3-Alkoxycarbonyl-2-oxazolones serve as easily handled reagents for amino protection, including tert-butoxycarbonylation, benzyloxycarbonylation, p-methoxybenzyloxycarbonylation, methoxycarbonylation and ethoxycarbonylation.For example, high yield N-protection of α-amino acids has been smoothly performed by the use of 3-tert-butoxycarbonyl and 3-benzyloxycarbonyl-2-oxazolones in aqueous solution at room temperature.A series of homopolymers, poly(3-alkoxycarbonyl-2-oxazolone), is readily obtainable by radical-initiated chain reaction of the corresponding 4,5-unsubstituted oxazolone monomers (except for the tert-butoxy derivate, which failed to give polymeric compounds), and these were successfully used for amino protection as well.Use of the polymer reagents greatly simplifies the purification procedure, though a longer reaction time is required.Keywords - 3-alkoxycarbonyl-2-oxazolone; poly(2-alkoxycarbonyl-2-oxazolone); 3-tert-butoxycarbonyl-2-oxazolone; 3-benzyloxycarbonyl-2-oxazolone; amino protection
- Kunieda, Takehisa,Higuchi, Tsunehiko,Abe, Yoshihiro,Hirobe, Masaaki
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p. 2174 - 2181
(2007/10/02)
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- Monitored Aminolysis of 3-Acyl-1,3-thiazolidine-2-thiones: Synthesis of Amides and Amide Alkaloids
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A functional heterocycle, 3-acyl-1,3-thiazolidine-2-thione has been shown to be effective as an acylating reagent for the amino group.ATT (1) was readily prepared by several methods, and reacted with various amino compounds in CHCl3, CH2Cl2, THF, EtOH, THF-H2O, or sulfolane to afford the corresponding amides, 2a-w and 3-10 in very high yields within a short time.This reagent exhibits high chemo-selectivity.Its reaction with the diamines 13 and 15 and the triamine 29, which include a primary amino group(s) and a secondary amino group, gave the products acylated only at the primary amino group(s), 14, 16, and 30, respectively, in high yields.Aminoalcohols and aminophenols were chemoselectively converted into acylaminoalcohols and acylaminophenols, respectively, by ATT (1).By utilizing this method, several amide alkaloids (26, 28, 30, and 34) were efficiently synthesized.This new aminolysis can be monitored by the disappearance of the yellow color of the starting materials, ATT (1); it is remarkably characteristic of this reaction. Keywords - monitored aminolysis; 3-acyl-1,3-thiazolidine-2-thione; high chemo-selectivity; amide synthesis; fagaramide; dolicotheline; spermidine; maytenine; N-ferulyltryptamine
- Nagao, Yoshimitsu,Seno, Kaoru,Kawabata, Kohji,Miyasaka, Tadao,Takao, Sachiko,Fujita, Eiichi
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p. 2687 - 2699
(2007/10/02)
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- 3-ACYL- AND 3-ALKOXYCARBONYL-2-OXAZOLONES AND THEIR HOMOPOLYMERS AS AMINO-PROTECTING REAGENTS
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3-Acyl and 3-alkoxycarbonyl-2-oxazolones as well as their homopolymers serve as practically usefull N-protecting reagents of amines including α-amino acids.
- Kunieda, Takehisa,Higuchi, Tsunehiko,Abe, Yoshihiro,Hirobe, Masaaki
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p. 3065 - 3066
(2007/10/02)
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