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  • Symmetrical Trichlorotriazine Derivatives as Efficient Reagents for One-Pot Synthesis of 3-Acetyl-2-chloroquinolines from Acetanilides under Vilsmeier–Haack Conditions
    Synlett (IF 2.151) Pub Date : 2017-08-28
    Muddam, Bhooshan, Venkanna, P., Venkateswarlu, M., Satish Kumar, M., Rajanna, K. C.

    Symmetrical trichlorotriazine derivatives such as 2,4,6-trichloro-1,3,5-triazine and trichloroisocyanuric acid were explored as Vilsmeier–Haack type reagents in the presence of N,N-dimethylacetamide for the effective synthesis of 3-acetyl-2-chloroquinolines from acetanilides. Ultrasonication led to shorter reaction times than conventional heating and gave yields comparable to those obtained under reflux conditions.

    更新日期:2017-08-29
  • Tetrabutylammonium Bifluoride as an Efficient Activating Agent for Copper-Catalyzed Vinylsilane Cross-Coupling Reactions
    Synlett (IF 2.151) Pub Date : 2017-08-25
    Cornelissen, Loïc, Nagy, Audric, Leyssens, Tom, Riant, Olivier

    Vinylsilanes are versatile and efficient nucleophiles in cross-coupling reactions. Herein is described the use of tetrabutylammonium bifluoride as a mild, cheap and scalable activating agent in several copper-catalyzed vinylsilane cross-couplings.

    更新日期:2017-08-26
  • Synthesis of Stereoselectively Functionalized Silacyclopentanes
    Synlett (IF 2.151) Pub Date : 2017-08-25
    Igawa, Kazunobu, Kuroo, Akihiro, Yoshihiro, Daisuke, Yamanaka, Yuki, Tomooka, Katsuhiko

    An efficient approach to a variety of chiral silacyclopentanes having silicon stereogenic center based on the stereospecific transformations of C4 carbon stereogenic center of silacyclopentenols by ­Mitsunobu reaction or Tsuji–Trost reaction has been developed. The thus obtained substitution products can be converted into novel silacyclopentane triols, amines, and carboxylic acids in stereospecific manner.

    更新日期:2017-08-26
  • DFT Studies Provide Mechanistic Insight into Nickel-Catalyzed Cross-Coupling Involving Organoaluminum-Mediated C–O Bond Cleavage
    Synlett (IF 2.151) Pub Date : 2017-08-25
    Yang, Ze-Kun, Wang, Chao, Uchiyama, Masanobu

    Density functional theory (DFT) calculations were performed to examine the reaction pathway of Ni-catalyzed cross-coupling with organoaluminum through C–O bond cleavage. The results indicate that the strong Lewis acidity of organoaluminums significantly facilitates the transmetalation step, but not the oxidative addition or reductive elimination step.

    更新日期:2017-08-26
  • New Triazole-Containing Branched Bis(dipeptidomimetic) – Switching from Self-Dimerization to Anion-Binding Properties
    Synlett (IF 2.151) Pub Date : 2017-08-25
    Chui, Tin-Ki, Chow, Hak-Fun

    A triazole-containing branched bis(dipeptidomimetic) 2 using l-lysine as a flexible branching unit was synthesized and characterized. The compound was found to form weak dimers (K dim = 19 M–1) in chloroform as shown by vapor pressure osmometry (VPO) and concentration-dependent 1H NMR studies. On the other hand, the compound was capable of binding chloride and monobasic diethyl phosphate (DEP) in chloroform. Job plot analysis, MALDI-TOF mass spectrometry, and NMR titration studies revealed a 1:1 binding stoichiometry with good binding affinities (K a ≈ 640–780 M–1). Structural studies using ­ROESY NMR spectroscopy and molecular modelling on the 2–DEP complex indicated the adoption of a helix-like conformation by the host with the guest situated near the branching juncture.

    更新日期:2017-08-26
  • Sequential O-Arylation/Lanthanide(III)-Catalyzed [3,3]-Sigmatropic Rearrangement of Bromo-Substituted Allylic Alcohols
    Synlett (IF 2.151) Pub Date : 2017-08-25
    Ramadhar, Timothy R., Kawakami, Jun-ichi, Batey, Robert A.

    Lanthanide(III)-catalyzed aryl-Claisen rearrangement of substrates bearing halo-substituted allyl groups, specifically 2-bromoallyl aryl ethers, afford ortho-2-bromoallylphenols. Aryl ether substrates were synthesized from brominated allylic alcohols via Mitsunobu reaction, Cu(II)-catalyzed arylation using potassium aryltrifluoroborate salts, or SNAr reaction. Aryl-Claisen rearrangements proceeded in moderate to excellent yields using Eu(III) catalysis. The alkenylbromide functionality remains intact, illustrating the compatibility of synthetically important alkenylhalides during C–O/C–C σ-bond migration processes. Subsequent derivatization of the ortho-2-bromoallylphenol products through O-alkylation or C-arylation/alkenylation via Suzuki–Miyaura cross-coupling demonstrate the potential to access densely-functionalized molecules.

    更新日期:2017-08-26
  • New Efficient Synthesis of 1,2,4-Trisubstituted Furans by a ­Sequential Passerini/Wittig/Isomerization Reaction Starting from Baylis–Hillman β-Bromo Aldehydes
    Synlett (IF 2.151) Pub Date : 2017-08-25
    Ren, Zhi-Lin, Sun, Mei, Guan, Zhi-Rong, Ding, Ming-Wu

    A new and efficient synthesis of 1,2,4-trisubstituted furans from a Baylis–Hillman β-bromo aldehyde, an acid, an isocyanide, and methyl(diphenyl)phosphine, by a sequential Passerini condensation, Wittig reaction, and isomerization in the presence of triethylamine is reported.

    更新日期:2017-08-26
  • Palladium-Catalyzed Cross-Coupling of 1,3,4-Oxadiazoles and Styrenes: An Efficient Method to Synthesize 2-Alkenyl-1,3,4- Oxadiazoles§
    Synlett (IF 2.151) Pub Date : 2017-08-25
    Salvanna, N., Reddy, P. Raghavendar, Das, Biswanath

    2-Alkenyl-1,3,4-oxadiazole derivatives have been prepared by cross-coupling of 1,3,4-oxadiazoles with styrenes by using palladium(II) trifluoroacetate [Pd(TFA)2] as a catalyst, 1,10-phenanthroline as a ligand, silver trifluoroacetate as an oxidant, and toluene as a solvent. The products were formed in high yields and no byproducts were detected.

    更新日期:2017-08-26
  • A Synthesis of Functionalized Thiazoles and Pyrimidine-4(3H)-thiones from 1,1,3,3-Tetramethylguanidine, Acetylenic Esters, and Aryl Isothiocyanates
    Synlett (IF 2.151) Pub Date : 2017-08-25
    Yavari, Issa, Amirahmadi, Asiyeh, Halvagar, Mohammad Reza

    Aryl isothiocyanates react with dialkyl 2-{[bis(dimethylamino)methylene]amino}maleates, generated from 1,1,3,3-tetramethylguanidine and acetylenic esters, to afford 2-(dimethylamino)-1,3-thiazole derivatives, functionalized 2-(dimethylamino)-6-thioxo-1,6-dihydropyrimidines, and ethyl 2-(dimethylamino)-6-[(4-nitrophenyl)im­ino]-4-phenyl-6H-1,3-thiazine-5-carboxylate, in moderate to good yields.

    更新日期:2017-08-26
  • Asymmetric Total Synthesis of (+)-Minfiensine by an Asymmetric Cascade Cyclization Strategy
    Synlett (IF 2.151) Pub Date : 2017-08-25
    Zhang, Ze-Xin, Chen, Si-Cong, Jiao, Lei

    The Strychnos alkaloid minfiensine and a series of akuammiline alkaloids, such as vincorine, aspidophylline A, and picrinine, possess a common core skeleton, a 4a,9a-heterocycle-fused tetrahydrocarbazole. Efficient construction of this core structure in a highly enantioselective manner would facilitate the total synthesis of these alkaloids. In this article, we briefly summarize the established strategies for obtaining this core structure, together with the corresponding total-synthesis routes, and we describe our own effort on the development of a new strategy, the asymmetric cascade dearomative cyclization, for the efficient total synthesis of (+)-minfiensine.

    更新日期:2017-08-26
  • Highly Active Manganese-Mediated Acylation of Alcohols with Acid Chlorides or Anhydrides
    Synlett (IF 2.151) Pub Date : 2017-08-24
    Joo, Seong-Ryu, Youn, Young-Jin, Hwang, Young-Ran, Kim, Seung-Hoi

    To explore further the practical uses of highly active manganese (Mn*), a variety of alcohols were treated with Mn*, and the resulting complexes were coupled with acid chlorides and/or acetic anhydride in the absence of any extra catalyst. The subsequent reactions took place smoothly under mild conditions, providing the corresponding O-acylation products in good to excellent isolated yields.

    更新日期:2017-08-25
  • Diastereoselective Palladium-Catalyzed Conjugate Addition of Arylboronic Acids to α-Substituted Cyclic Enones
    Synlett (IF 2.151) Pub Date : 
    Gao, Ang, Liu, Xiu-Yan, Ding, Chang-Hua, Hou, Xue-Long

    A palladium-catalyzed conjugate addition of arylboronic acids to α-substituted cyclic enones was developed to give α,β-disubstituted ketones with high diastereoselectivity. Mechanistic investigation showed that the high diastereoselectivity was realized through epimerization.

    更新日期:2017-08-24
  • Regioselectivity of Mercury-Promoted Oxacyclizations of Alkynyl Diols
    Synlett (IF 2.151) Pub Date : 
    Hurtak, Jessica A., McDonald, Frank E.

    Hg(OTf)2-catalyzed cyclization of an alkynyl alcohol on a tetra­hydropyran template gives the bispyranyl ketone arising from dehydrative cyclization and alkyne hydration, rather than the targeted fused pyran-oxepane product. The combination of stoichiometric Hg(OTf)2 and triethylsilane gives reductive cyclization, but affords the fused pyran-oxocane corresponding to an 8-endo-mode oxacyclization process.

    更新日期:2017-08-24
  • Biology-Oriented Synthesis of Decahydro-4,8-epoxyazulene Scaffolds
    Synlett (IF 2.151) Pub Date : 2017-08-23
    Jia, Zhi-Jun, Merten, Christian, Knauer, Lena, Murarka, Sandip, Strohmann, Carsten, Waldmann, Herbert

    Guided by the principle of biology-oriented synthesis, a collection of compounds with decahydro-4,8-epoxyazulene scaffold occurring in bioactive natural products was synthesized by the rhodium(II)-catalyzed 1,3-dipolar cycloaddition reaction of pentafulvenes and carbonyl ylides. The products can be obtained in moderate to high yields, with moderate enantioselectivity and excellent diastereoselectivity and regioselectivity.

    更新日期:2017-08-24
  • A General Strategy for the Preparation of Thalidomide-Conjugate Linkers
    Synlett (IF 2.151) Pub Date : 2017-08-23
    Papatzimas, James W., Gorobets, Evgueni, Brownsey, Duncan K., Maity, Ranjan, Bahlis, Nizar J., Derksen, Darren J.

    The synthesis of small-molecule linkers for installation of thalidomide-based conjugates is described. Linker properties have been recognized as vital to conjugate success in drug discovery and delivery systems. These small-molecule tethers act as linkages between molecules, can also aid in cell permeability, and act as solubilizing agents. This work shows our progress in synthesizing conjugates with a variety of linker characteristics. The adaptability and manipulation of these and other linkers holds potential in improving synthetic control of chemical connectivities toward therapeutic development.

    更新日期:2017-08-24
  • Transition-Metal-Free Reactions Between Boronic Acids and N-Sulfonylhydrazones or Diazo Compounds: Reductive Coupling Processes and Beyond
    Synlett (IF 2.151) Pub Date : 2017-08-22
    Paraja, Miguel, Plaza, Manuel, Valdés, Carlos

    The metal-free reaction between diazo compounds and boronic acids has been established in recent years as a powerful C(sp3)–C bond-forming reaction. This account covers the recent advances in this area. First, the various synthetic applications of reactions with N-sulfonylhydrazones as a convenient source of diazo compounds is discussed. These transformations can be regarded as reductive couplings of carbonyl compounds. Also covered is the incorporation of other mild sources of diazo compounds in these reactions: diazotization of amines and oxidation of hydrazones. Finally, the development of sequential and cascade processes is presented.

    更新日期:2017-08-23
  • Iodine-Catalyzed Regioselective Sulfenylation of 4H-Pyrido[1,2-a]pyrimidin-4-ones with Sulfonyl Hydrazides
    Synlett (IF 2.151) Pub Date : 2017-08-22
    Liu, Wenjie, Wang, Shaohua, Cai, Zhihao, Li, Ziying, Liu, Jianwen, Wang, Anda

    A simple and efficient method for direct sulfenylation of 4H-pyrido[1,2-a]pyrimidin-4-ones with sulfonyl hydrazides has been developed. The transformation is catalyzed by iodine under metal-free conditions with high regioselectivity and good functional-group tolerance.

    更新日期:2017-08-23
  • A Solvent-Free Reaction for Silyl Enol Ethers Synthesis
    Synlett (IF 2.151) Pub Date : 2017-08-22
    Morozzi, Chiara, Rosati, Ornelio, Curini, Massimo, Lanari, Daniela

    Silyl enol ethers are extremely useful nucleophilic intermediates for chemical transformations because they are synthetically versatile substrates for a wide range of C–C bond-forming reactions. Here, we present a new, mild, and solvent-free procedure for the synthesis of silyl enol ethers that employs a catalytic amount of solid-supported base and an equimolar amount of N,O-(bistrimethylsilyl)acetamide as a silylating agent.

    更新日期:2017-08-23
  • Regioselective Ylide Formation on Acetal-Functionalized Trialkyl Phosphonium Salts: Extending the Scope of Carbonyl Homologation
    Synlett (IF 2.151) Pub Date : 2017-08-22
    Narayanappa, Arkesh, Hurem, David, McNulty, James

    The discovery of a complex-induced proximity effect and scope of regioselective ylide formation on acetal- and ketal-functionalized trialkylphosphine-derived phosphonium salts is explored as a route to homologated unsaturated carbonyl derivatives.

    更新日期:2017-08-23
  • Enantioselective Palladium-Catalyzed Decarboxylative Allylation of β-Keto Esters Assisted by a Thiourea
    Synlett (IF 2.151) Pub Date : 2017-08-22
    Qian, Hua, Gu, Guoxian, Zhou, Qinghai, Lu, Jiaxiang, Chung, Lung Wa, Zhang, Xumu

    Enantioselective intramolecular decarboxylative allylation of β-keto esters catalyzed by a palladium bis(phosphine)-thiourea complex is reported. This procedure is not only effective for β-keto esters, but also effective for β-keto amides. An intermolecular variant of the asymmetric decarboxylative allylation is also established. DFT calculations indicate that an outer-sphere mechanism is viable for the decarboxylative allylation of β-keto esters.

    更新日期:2017-08-23
  • 4-Ethoxy-1,1,1-trifluoro-3-buten-2-one (ETFBO), a Versatile Precursor for Trifluoromethyl-Substituted Heteroarenes – a Short Synthesis of Celebrex® (Celecoxib)
    Synlett (IF 2.151) Pub Date : 2017-08-22
    Sommer, Heiko, Braun, Max, Schröder, Benjamin, Kirschning, Andreas

    4-Ethoxy-1,1,1-trifluoro-3-buten-2-one (ETFBO) serves as a trifluoromethyl-containing building block for the preparation of trifluoromethyl-substituted thiophenes, furans, pyrrols, and piperazines. Key steps are an addition–elimination reaction to ETFBO followed by the thiazolium-catalyzed Stetter reaction. The scope of this chemistry was demonstrated in a new synthetic approach towards the COX-2 selective, nonsteroidal anti-inflammatory drug Celebrex® (celecoxib).

    更新日期:2017-08-23
  • Trapping of Hexadehydro-Diels–Alder Benzynes with Exocyclic, Conjugated Enals as a Route to Fused Spirocyclic Benzopyran Motifs
    Synlett (IF 2.151) Pub Date : 2017-08-22
    Wang, Tao, Oswood, Christian J., Hoye, Thomas R.

    Exocyclic, conjugated enals react with benzynes generated by heating various triyne-containing substrates to produce spirocyclic benzopyran derivatives. These products are consistent with a mechanistic sequence that involves initial net [2+2] cycloaddition of the benzyne and aldehyde followed by 4π-electrocyclic ring opening and 6π ring closing.

    更新日期:2017-08-23
  • Photoinduced Regioselective Lactonization of ortho-Iodobenzoic Acids with Alkenes: Synthesis of 3,4-Dihydroisocoumarin Derivatives
    Synlett (IF 2.151) Pub Date : 2017-08-22
    Zhang, Xiao, Huang, Binbin, Yang, Chao, Xia, Wujiong

    A photoinduced strategy for the synthesis of a variety of 3,4-dihydroisocoumarins has been realized. The reactions proceeded from ortho-iodobenzoic acids and alkenes through a photodehalogenative lactonization with NaHCO3 as the only additive in dimethyl sulfoxide (DMSO) to provide the desired products in moderate to good yields. This method offers a simple, mild, and environmentally friendly route to 3,4-dihydroisocoumarin derivatives.

    更新日期:2017-08-23
  • Syntheses of Dimeric Securinega Alkaloids
    Synlett (IF 2.151) Pub Date : 2017-08-22
    Jeon, Sangbin, Park, Joonoh, Han, Sunkyu

    The isolation of flueggenines A and B by Yue and co-workers in 2006 has triggered a burst of isolation reports of dimeric and oligomeric securinega alkaloid natural products. The compelling molecular structures of these compounds with various modes of connection between monomeric securinega units have posed intriguing challenges to the synthetic organic community. Herein, we have categorized high-order securinega alkaloids based on their biosynthetic mode of dimerization or oligomerization. We then have compiled all reported syntheses of dimeric securinega alkaloids based on our classification.

    更新日期:2017-08-23
  • Highly Strained para-Phenylene-Bridged Macrocycles from Unstrained 1,4-Diketo Macrocycles
    Synlett (IF 2.151) Pub Date : 2017-08-22
    Mitra, Nirmal K., Merryman, Caroline P., Merner, Bradley L.

    The conversion of macrocyclic 1,4-diketones to highly strained para-phenylene rings has recently been reported by our laboratory. This synthetic strategy represents a non-cross-coupling-based approach to arene-bridged macrocycles, and an alternative to palladium- and nickel-mediated processes. In this Synpacts article we discuss the development of endgame aromatization protocols for the synthesis of increasingly strained arene systems, as well as potential advantages of the macrocyclic 1,4-diketone approach to selectively functionalized benzenoid macrocycles for future complexity building reactions.

    更新日期:2017-08-23
  • Heterocyclic Chemistry – Old Science or the Forefront of Chemistry?
    Synlett (IF 2.151) Pub Date : 2017-08-21
    Reiser, Oliver

    Oliver Reiser studied chemistry at the Universities of Hamburg, Jerusalem and Los Angeles (UCLA) and earned his Ph.D. degree from the University of Hamburg (Prof. Armin de Meijere) in 1989. After postdoctoral stays at IBM Research Center (Dr. Robert D. Miller) and Harvard University (Prof. David A. Evans), he started his independent research in 1992 at the University of Göttingen. In 1996, he moved to the University of Stuttgart as an Associate Professor and in 1997, to the University of Regensburg as Professor of Chemistry. His research group specializes in catalysis starting from renewable resources such as furans and pyrroles toward fine chemicals, natural products and drugs. He is currently serving as President of the International Society of Heterocyclic Chemistry.

    更新日期:2017-08-22
  • Unexpected Rearrangement of 2-Bromoaniline under Biphasic Alkylation Conditions
    Synlett (IF 2.151) Pub Date : 2017-08-21
    Barraza, Scott J., Denmark, Scott E.

    Alkylation of 2-bromoaniline with benzyl bromide under ostensibly basic N-alkylation conditions resulted in migration of bromine from the 2- to the 4-aryl position. Herein we report our studies to elucidate the mechanism of this rearrangement with the objective of suppressing this unexpected outcome. We find that careful choice of reagents is critical, and that this behavior may be extrapolated to alkylation reactions of electron-rich bromo- and iodoanilines in general.

    更新日期:2017-08-22
  • Diastereoselective Lithiation of N-Benzyl Pyrroloimidazolones Derived from l-Proline Hydantoin
    Synlett (IF 2.151) Pub Date : 2017-08-21
    Emberson, Kassandra, Tran, Ngan, Metallinos, Costa

    An N-benzyl pyrroloimidazolone derived from l-proline hydantoin undergoes asymmetric lithiation with n-BuLi/TMEDA in toluene to give products of electrophile quench (E+) that range from 87:13 to 91:9 diastereomeric ratio (dr). All products appear to have the same relative stereochemistry as determined by transmetalation of benzylic stannanes, which gave identical major diastereomers for several products as to what was observed by direct lithiation–substitution of the starting material. X-Ray crystallography of the major diastereomer of the benzophenone adduct established (R)-configuration at the benzylic center, i.e., anti stereochemistry with respect to the imidazolone. Lithiation of a selectively deuterated analogue of the starting material according to the optimized conditions, followed by benzophenone quench, gave diastereomeric products with far lower selectivity (53:47 dr) than lithiation of the non-deuterated analogue (91:9 dr) owing to a large primary kinetic isotope effect. These preliminary results imply that metalation of the N-benzyl pyrroloimidazolone may follow an asymmetric deprotonation pathway to give a benzylic carbanion that retains its configuration during electrophile quench.

    更新日期:2017-08-22
  • Catalytic Deuteration of Aldehydes with D2O
    Synlett (IF 2.151) Pub Date : 2017-08-21
    Isbrandt, Eric S., Vandavasi, Jaya Kishore, Zhang, Wanying, Jamshidi, Mohammad P., Newman, Stephen G.

    A procedure is presented that enables the direct deuteration of the formyl C–H bond of aldehydes using D2O as the deuterium source and commercially available RuHCl(CO)(PPh3)3 as the catalyst. Up to 84% deuterium incorporation can be achieved in a single experiment. Multiple iterations can be carried out to further increase the deuteration.

    更新日期:2017-08-22
  • Rapid Continuous Ruthenium-Catalysed Transfer Hydrogenation of Aromatic Nitriles to Primary Amines
    Synlett (IF 2.151) Pub Date : 2017-08-21
    Labes, Ricardo, González-Calderón, Davir, Battilocchio, Claudio, Mateos, Carlos, Cumming, Graham R., de Frutos, Oscar, Rincón, Juan A., Ley, Steven V.

    A continuous flow method for the selective reduction of aromatic nitriles to the corresponding amine is reported. The method is based on a ruthenium-catalysed transfer-hydrogenation process, requires no additives, and uses isopropanol as both solvent and reducing agent. The process utilizes 1 mol% of the commercially available [Ru(p-cymene)Cl2]2, with a residence time of ca. 9 min, and a throughput of 50 mmol/h. The method was successfully applied to a range of aromatic nitriles providing the corresponding primary amines in good yields.

    更新日期:2017-08-22
  • Chemistry 2.0: Developing a New, Solvent-Free System of Chemical Synthesis Based on Mechanochemistry
    Synlett (IF 2.151) Pub Date : 2017-08-17
    Do, Jean-Louis, Friščić, Tomislav

    Mechanochemistry by grinding or milling has grown from a laboratory curiosity to a versatile approach for the synthesis and discovery of molecules, materials and reactivity. Focusing on organic synthesis and the chemistry of organic solids in general, we now provide a snapshot of this exciting, rapidly developing area, with the intention to illustrate its potential in establishing a more efficient and environmentally friendly system of chemical and materials synthesis, based on solid-state transformations rather than conventional, solution-dependent chemistry.

    更新日期:2017-08-17
  • Rhodium-Catalyzed Reductive Cleavage of Aryl Carbamates Using Isopropanol as a Reductant
    Synlett (IF 2.151) Pub Date : 2017-08-17
    Yasui, Kosuke, Higashino, Masaya, Chatani, Naoto, Tobisu, Mamoru

    Despite the widespread use of carbamates as a directing group in C–H bond-functionalization reactions, reductive removal of this directing group is not straightforward. Currently available methods are limited to nickel-catalyzed reactions using i PrMgX or hydrosilane as a reductant, leaving the functional group compatibility issue to be solved. Herein, we report rhodium-catalyzed reductive cleavage of aryl carbamates using iPrOH as a milder reductant.

    更新日期:2017-08-17
  • Lithiation–Substitution of N-Boc-2-phenylazepane
    Synlett (IF 2.151) Pub Date : 2017-08-17
    Aeyad, Tahani, Williams, Jason D., Meijer, Anthony J. H. M., Coldham, Iain

    Preparation of 2,2-disubstituted azepanes was accomplished from N-tert-butoxy(N-Boc)-2-phenylazepane by treatment with butyllithium then electrophilic quench. The lithiation was followed by in situ ReactIR spectroscopy and the rate of rotation of the carbamate was determined by variable temperature (VT)-NMR spectroscopy and by DFT studies. Most electrophiles add α to the nitrogen atom but cyanoformates and chloroformates gave ortho-substituted products. Cyclic carbamates were formed from an aldehyde or ketone electrophile. Kinetic resolution with sparteine was only poorly selective. Removal of the Boc group promoted cyclization to a homoindolizidine or an isoindolinone.

    更新日期:2017-08-17
  • Synthesis of Novel BTPhen-Functionalized Silica-Coated Magnetic Nanoparticles for Separating Trivalent Actinides and Lanthanides
    Synlett (IF 2.151) Pub Date : 2017-08-17
    Afsar, Ashfaq, Cowell, Joseph, Distler, Petr, Harwood, Laurence M., John, Jan, Westwood, James

    Bis-(1,2,4-triazin-3-yl)-1,10-phenanthroline (BTPhen) functionalized magnetic nanoparticles (MNPs), which selectively extract Am(III) over europium(III) from 0.1 M HNO3 with fast kinetics and a separation factor of 30 have been synthesized. These MNPs also show a small but significant selectivity for Am(III) over Cm(III) with a separation factor of around 3 in 0.1 M HNO3. We report also the synthesis of these BTPhen and related ligands via an improved synthetic route bypassing the problematic benzylic oxidation with stoichiometric SeO2.

    更新日期:2017-08-17
  • Selective Oxidation of Secondary Amines to N,N-Disubstituted Hydroxylamines by Choline Peroxydisulfate
    Synlett (IF 2.151) Pub Date : 2017-08-17
    Banan, Alireza, Valizadeh, Hassan, Heydari, Akbar, Moghimi, Abolghasem

    N,N-Disubstituted hydroxylamines were prepared directly from secondary amines by a reliable method using an oxidizing task-specific ionic liquid, choline peroxydisulfate. The operational simplicity, high selectivity, and green reaction conditions, make this method efficient and practical.

    更新日期:2017-08-17
  • Copper-Catalyzed Asymmetric 1,2-Addition of Grignard Reagents to 3-Acyl 2H-chromenes
    Synlett (IF 2.151) Pub Date : 2017-08-17
    Calvo, Beatriz C., Minnaard, Adriaan J.

    Enones in which the carbon–carbon double bond is part of the pharmacologically important 2H-chromene (2H-1-benzopyran) nucleus undergo asymmetric copper-catalyzed 1,2-addition of Grignard reagents. High yields and enantiomeric excesses up to 84% are obtained and access to these novel enantio-enriched tertiary alcohols is provided.

    更新日期:2017-08-17
  • Photochemistry of ortho-Azidocinnamoyl Derivatives: Facile and Modular Synthesis of 2-Acylated Indoles and 2-Substituted Quinolines under Solvent Control
    Synlett (IF 2.151) Pub Date : 2017-08-17
    Chaabouni, S., Pinkerton, N. M., Abid, S., Galaup, C., Chassaing, S.

    The light-promoted potential of ortho-azidocinnamoyl compounds is evaluated for heterocycle synthesis. Depending on the nature of the solvent, 2-acylated indoles were obtained under aprotic conditions, whereas the use of a protic medium led to 2-substituted quinolines. The synthetic significance of this metal-free method is that, by simply changing the solvent, the reaction outcome can be directed towards different key heterocyclic scaffolds.

    更新日期:2017-08-17
  • N-Arylation of Heterocycles by a Tandem Aza-Michael Addition Reaction and Aromatization Sequence
    Synlett (IF 2.151) Pub Date : 2017-08-17
    Chittimalla, Santhosh Kumar, Nakka, Srinuvasu, Koodalingam, Manikandan, Bandi, Chennakesavulu

    Cyclohexa-2,4-dien-1-one derivatives, upon reaction with N-heterocycles in the presence of scandium(III) triflate, underwent a tandem Michael addition reaction followed by aromatization of the ­Michael adduct generated in situ to give N-aryl heterocycles in good yields. Because of the ready accessibility of variously substituted cyclohexa-2,4-dien-1-ones, a range of N-aryl heterocycles have become available.

    更新日期:2017-08-17
  • Palladium-Catalyzed Arylation of Benzylic C–H Bonds of Azaarylmethanes with Aryl Sulfides
    Synlett (IF 2.151) Pub Date : 2017-08-17
    Gao, Ke, Yamamoto, Keita, Nogi, Keisuke, Yorimitsu, Hideki

    Benzylic C–H arylation of azaarylmethanes with aryl sulfides has been developed by using a Pd-NHC catalyst and an amide base. Various azaarylmethanes and aryl sulfides were involved in the reaction to afford the corresponding diarylmethanes in good to excellent yields. Moreover, triarylmethane synthesis was accomplished through iterative arylations of 2- or 4-methylpyridine with two different aryl sulfides.

    更新日期:2017-08-17
  • Palladium-Catalysed Sonogashira Reactions of 16-(Hydroxymethylidene)-3-methoxy-α-estrone
    Synlett (IF 2.151) Pub Date : 2017-08-17
    Jopp, Stefan, Liesegang, Marko, Ehlers, Peter, Frank, Eva, Schneider, Gyula, Wölfling, János, Villinger, Alexander, Langer, Peter

    Sonogashira reactions of steroids have been studied. The reaction of α-estron-16-methylidenyloxy triflate with various alkynes afforded novel alkynylvinylidene steroids. The reactions proceeded in good to quantitative yields, with excellent E-selectivity and with a broad synthetic scope.

    更新日期:2017-08-17
  • Synthesis of Cyanamides from Cyanogen Bromide under Mild Conditions through N-Cyanation of Allylic Tertiary Amines
    Synlett (IF 2.151) Pub Date : 2017-08-17
    Liang, Honggang, Bao, Lingxiang, Du, Yao, Zhang, Yiying, Pang, Siping, Sun, Chenghui

    Cyanamides were selectively formed through a one-step nucleophilic substitution reaction of allylic tertiary amines with cyanogen bromide. Because of the mild reaction conditions and good yields of the reaction, as well as the commercial availability of the starting materials, this new method represents a valuable tool for the synthesis of cyan­amides through an N-deallylation reaction and an N-cyanation reaction in one pot.

    更新日期:2017-08-17
  • Synthetic Studies Towards the Synthesis of 6-Substituted 3-Fluoro-5,6-dihydropyran-2-ones
    Synlett (IF 2.151) Pub Date : 2017-08-17
    Mandal, Samir K., Sarkar, Apurba, Chakraborty, Puskin, Chattopadhyay, Ashoke P.

    The synthesis of 6-substituted 3-fluoro-5,6-dihydropyran-2-ones under mild conditions is described. The key step of the synthesis involves a Julia–Kocienski olefination.

    更新日期:2017-08-17
  • Nicholas Reactions of Alkynyl- and Alkenyltrifluoroborates
    Synlett (IF 2.151) Pub Date : 2017-08-17
    Onge, Brent St., Green, James R.

    The Lewis acid mediated Nicholas reaction of potassium alkynyltrifluoroborates and propargyl acetate-hexacarbonyldicobalt complexes affords 1,4-diyne dicobalt hexacarbonyl complexes in good yields. The analogous Nicholas reactions of potassium alkenyltrifluoro­borates give 1,3-enyne dicobalt hexacarbonyl complexes in most cases, although the initial site of reaction can vary. Potassium vinyltrifluoroborate itself affords alkynylcyclopropane complexes.

    更新日期:2017-08-17
  • An Efficient and Practical Process for the Synthesis of Glimepiride
    Synlett (IF 2.151) Pub Date : 2017-08-17
    Tanwar, Dinesh Kumar, Surendrabhai, Vaghela Ravikumar, Gill, Manjinder Singh

    A novel and simple approach to the synthesis of glimepiride is reported. It involves the preparation of a carbamate of 3-ethyl-4-methyl-1H-pyrrol-2(5H)-one, followed by its reaction with 4-(2-aminoethyl)benzenesulfonamide to produce the intermediate sulfonamide. This sulfonamide, upon reaction with phenyl (trans-4-methylcyclohexyl)carbamate, gave glimepiride. This process avoids the use of phosgene, isocyanates, or chloroformates. Furthermore, sulfonation of the aryl group was eliminated, rendering the product free of the impurities reported in earlier processes.

    更新日期:2017-08-17
  • Rhodium-Catalyzed Regioselective C7-Functionalization of Indole Derivatives with Acrylates by Using an N-Imino Directing Group
    Synlett (IF 2.151) Pub Date : 2017-08-17
    Xu, Lanting, Tan, Lushi, Ma, Dawei

    An efficient rhodium-catalyzed method for C–H olefination at the C7 position of indoles has been developed. The N-imino directing group was shown to be crucial for high regioselectivity and reactivity of the metal catalyst. The utility of this protocol was further demonstrated through a concise, four-step synthesis of pyroquilon from indole.

    更新日期:2017-08-17
  • Tracking On-Surface Chemistry with Atomic Precision
    Synlett (IF 2.151) Pub Date : 2017-08-17
    Jacobse, Peter H., Moret, Marc-Etienne, Klein Gebbink, Robertus J. M., Swart, Ingmar

    The field of on-surface synthesis has seen a tremendous development in the past decade as an exciting new methodology towards atomically well-defined nanostructures. A strong driving force in this respect is its inherent compatibility with scanning probe techniques, which allows one to ‘view’ the reactants and products at the single-molecule level. In this article, we review the ability of noncontact atomic force microscopy to study on-surface chemical reactions with atomic precision. We highlight recent advances in using noncontact atomic force microscopy to obtain mechanistic insight into reactions and focus on the recently elaborated mechanisms in the formation of different types of graphene nanoribbons.

    更新日期:2017-08-17
  • Visible-Light-Mediated Synthesis of Pyrazines from Vinyl Azides Utilizing a Photocascade Process
    Synlett (IF 2.151) Pub Date : 2017-08-16
    Hossain, Asik, Pagire, Santosh K., Reiser, Oliver

    A convenient method for the synthesis of substituted pyrazines from vinyl azides has been developed. This method is enabled by a dual-energy and electron-transfer strategy by visible-light photocatalysis. Initially, vinyl azides are activated by a triplet sensitization process from an excited ruthenium photocatalyst in the presence of water to form dihydropyrazines, followed by a single-electron-transfer (SET) process under oxygen (air) atmosphere that leads to the tetrasubstituted pyrazines in good to excellent yields.

    更新日期:2017-08-16
  • Taming Silylium Ions for Synthesis: N-Heterocycle Synthesis via Stereoselective C–C Bond Formation
    Synlett (IF 2.151) Pub Date : 2017-08-16
    Moyer, Brandon S., Gagné, Michel R.

    Silylium ions (formally [R3Si]+) have long been the subject of investigations and significant debate in both theoretical and experimental chemistry, but few catalytic, synthetic applications have been reported due to the exceptionally high reactivity and Lewis acidity of these elusive species. Results to be discussed include the application of easily accessible silylium ion catalysts to the stereoselective synthesis of various N-heterocyclic pyrrolidine and piperidine scaffolds. The tested substrates are derived from the chiral pool and can be obtained in three high-yielding steps from amino alcohols; subsequent stereoselective silylium ion catalyzed Prins cyclization and trapping with R3Si–Nu nucleophiles (e.g., Nu = H, allyl, azide, and enol ethers) results in novel nitrogen-containing polycyclic scaffolds with potential medicinal chemistry applications.

    更新日期:2017-08-16
  • A Bench-Stable Vilsmeier Reagent for in situ Alcohol Activation: Synthetic Application in the Synthesis of 2-Amino-2-Thiazolines
    Synlett (IF 2.151) Pub Date : 2017-08-16
    Corbett, Michael T., Caille, Seb

    A robust, chemoselective direct condensation/cyclization of thioureas and amino alcohols is described. Employing a bench-stable Vilsmeier reagent, methoxymethylene-N,N-dimethyliminium methyl sulfate, the selective in situ activation of alcohols is achieved with high efficiency and broad functional-group tolerance. The reversible interaction of the Vilsmeier reagent with substrate was key to the success of this activation strategy.

    更新日期:2017-08-16
  • Efforts Toward a Synthesis of Crotogoudin and Crotobarin
    Synlett (IF 2.151) Pub Date : 2017-08-16
    Mai, Duy N., Uchenik, Dmitriy, Vanderwal, Christopher D.

    Two synthesis designs for the diterpenoid crotogoudin are discussed, and efforts to achieve each are described. First, a Cope rearrangement/intramolecular Diels–Alder cascade reaction was investigated. Second, a bioinspired sequence of cationic bicyclization and A-ring oxidative fragmentation set-up for a lactonization induced by a phenolic oxidation, ultimately providing a tricyclic intermediate that required only installation of the bridging ring of the salient bicyclo[2.2.2]octane system. This last endeavor was fraught with difficulty, but did lead to the development of conditions for cyclization of related keto-alkenes via manganese(III)-based radical chemistry.

    更新日期:2017-08-16
  • Concise Synthesis of Lamellarin Alkaloids by C–H/N–H Activation: Evaluation of Metal Catalysts in Oxidative Alkyne Annulation
    Synlett (IF 2.151) Pub Date : 2017-08-16
    Mei, Ruhuai, Zhang, Shou-Kun, Ackermann, Lutz

    The performance of various transition-metal catalysts was explored in the step-economical synthesis of naturally occurring lamellarin alkaloids by C–H/N–H activation. The oxidative alkyne annulation proceeded efficiently by using sustainable ruthenium(II) catalysis, which set the stage for a concise synthesis of lamellarin D, lamellarin H and derivatives thereof.

    更新日期:2017-08-16
  • Pursuit of Enantioselective Synthesis of Heterocycle-Bearing ­Stereocenters: The Development of a Stereocontrolled BINOL-­Catalyzed Conjugate Addition of Organoboron Nucleophiles
    Synlett (IF 2.151) Pub Date : 2017-08-15
    May, Jeremy A., Nguyen, Thien S., Nguyen, Truong N., Le, Phong Q., Chen, Po-An, Vallakati, Ravikrishna

    This account chronicles the iterative development of an enantioselective conjugate addition of organoboron nucleophiles to α,β-unsaturated enones and enals catalyzed by BINOL derivatives. Beginning with a specific application of this transformation to the total synthesis of the flinderole alkaloids, the transformation progressed to encompass a much larger scope of heterocycle-substituted electrophiles. The next phase saw progress toward the use of a broader scope of functional nucleophiles, with application in a strategy to synthesize discoipyrrole D. At each stage of this chronologically organized discussion, key problems, hypotheses, and solutions are presented to show the sources of discovery and solutions to problems as the catalyst and other reaction components were made more reactive. The interplay of target-directed reaction development, efforts to increase the scope of compatible functional groups, mechanistic studies, and empirical exploration is described to illustrate sources of chemical discovery.

    更新日期:2017-08-15
  • Sharpless Asymmetric Dihydroxylation on α,β-Unsaturated Diazoketones: A New Entry for the Synthesis of Disubstituted Furanones
    Synlett (IF 2.151) Pub Date : 2017-08-15
    Talero, Alexánder G., Burtoloso, Antonio C. B.

    The synthesis of enantiomerically pure 4,5-disubstituted 2-furanones is accomplished in three steps from aldehydes. The steps involve a highly enantioselective Sharpless asymmetric dihydroxylation of α,β-unsaturated diazoketones, followed by a photochemical Wolff rearrangement.

    更新日期:2017-08-15
  • A One-Pot Methodology for the Synthesis of the Yohimban Skeleton
    Synlett (IF 2.151) Pub Date : 2017-08-15
    Parra, Claudio, Solís, Pablo, Bonjoch, Josep, Bradshaw, Ben

    A simple and straightforward assembly of the yohimban skeleton was achieved by condensation of an acyclic β-keto ester with tryptamine, followed by consecutive cross metathesis and tandem cyclization reactions, leading to the formation of three new rings. The whole process was readily carried out in the one-flask providing a rapid entry to the pentacyclic scaffold of yohimbine alkaloids.

    更新日期:2017-08-15
  • Synthesis of (–)-Muricatacin and (–)-(R,R)-L-Factor Involving an Organocatalytic Direct Vinylogous Aldol Reaction
    Synlett (IF 2.151) Pub Date : 2017-08-14
    Cooze, Christopher, Manchoju, Amarender, Pansare, Sunil V.

    Concise syntheses of the polyketide natural product (–)-muricatacin and (–)-(R,R)-L-factor (natural product enantiomer) were achieved in four steps by employing an organocatalytic asymmetric direct vinylogous aldol reaction of γ-crotonolactone and suitable aliphatic aldehydes as the key step.

    更新日期:2017-08-15
  • Iron-Catalyzed C3-Formylation of Indoles with Formaldehyde and Aqueous Ammonia under Air
    Synlett (IF 2.151) Pub Date : 2017-08-14
    Wang, Qing-Dong, Zhou, Bin, Yang, Jin-Ming, Fang, Dong, Ren, Jiangmeng, Zeng, Bu-Bing

    An efficient iron-catalyzed C3-selective formylation of free (N–H) or N-substituted indoles was developed by employing formaldehyde and aqueous ammonia, with air as the oxidant. This new method gave 3-formylindoles in moderate to excellent yields with fairly short reaction times. Moreover, this procedure for catalytic formylation of indoles can be applied to gram-scale syntheses.

    更新日期:2017-08-15
  • Nef–Perkow–Mumm Cascade towards Imido Phosphate Derivatives
    Synlett (IF 2.151) Pub Date : 2017-08-11
    Dos Santos, Aurélie, Cordier, Marie, El Kaïm, Laurent

    A one-pot, four-component synthesis of imido phosphates has been achieved using a Nef–Perkow sequence followed by addition of carboxylic acid derivatives. The final imido moiety is formed via a Mumm rearrangement of an intermediate imidate.

    更新日期:2017-08-12
  • Nonenzymatic Biomimetic Synthesis of Black Tea Pigment Theaflavins
    Synlett (IF 2.151) Pub Date : 2017-08-11
    Matsuo, Yosuke, Oowatashi, Ryosuke, Saito, Yoshinori, Tanaka, Takashi

    Theaflavins are reddish-orange black tea pigments with a benzotropolone chromophore, and their various biological activities have been reported. Theaflavins are produced by oxidative coupling between catechol-type and pyrogallol-type catechins via bicyclo[3.2.1]octane-type intermediates. In this study, a new method for nonenzymatic biomimetic synthesis of theaflavins was developed using the DPPH radical as an oxidizing agent.

    更新日期:2017-08-12
  • β-Lactam-Synthon-Interceded Metal/Acid-Free Diastereoselective Access to Highly Functionalized Oxazol-5-ones and Dihydroimidazoles
    Synlett (IF 2.151) Pub Date : 2017-08-11
    Singh, Amandeep, Kaur, Harleen, Sharma, Palak, Anand, Amit, Kumar, Vipan

    Facile diastereoselective access to functionalized oxazol-5-ones and dihydroimidazoles was accomplished through base-promoted intramolecular amidolysis and methoxide-assisted tandem intramolecular amidolysis/ring opening/intramolecular cyclization, respectively, of C-3-functionalized azetidin-2-ones.

    更新日期:2017-08-12
  • Asymmetric Synthesis of Pyrrolizidines, Indolizidines and Quinolizidines via a Double Reductive Cyclisation Protocol
    Synlett (IF 2.151) Pub Date : 2017-08-08

    This account describes an overview of the asymmetric syntheses of pyrrolizidines, indolizidines and quinolizidines via a common double reductive cyclisation protocol. The highly diastereoselective conjugate addition of an enantiopure lithium amide to an α,β-unsaturated ester incorporating a terminal C=C bond installed the nitrogen-bearing stereogenic centre and was followed by enolate functionalisation to introduce the second olefinic functionality. Alternatively, conjugate addition to the corresponding α-alkenyl α,β-unsaturated ester followed by α-protonation of the intermediate enolate may also be used to access the cyclisation precursor. After oxidation of the two terminal olefinic units to give the corresponding dialdehyde, tandem hydrogenolysis/hydrogenation was employed to efficiently construct the azabicyclic core of each target molecule. This double reductive cyclisation strategy was successfully utilised in the syntheses of 13 azabicyclic alkaloids or closely related analogues.

    更新日期:2017-08-09
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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