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Showing papers in "Synlett in 2014"


Journal ArticleDOI
10 Jul 2014-Synlett
TL;DR: In this paper, formic acid derivatives are used as carbon monoxide (CO) surrogates in synthetic organic chemistry, in terms of their good availability, stability, and ease of handling.
Abstract: This account describes our findings on formic acid derivatives as practical carbon monoxide (CO) surrogates in synthetic organic chemistry. Among the known CO surrogates, formic acid derivatives are advantageous in terms of their good availability, stability, and ease of handling. We adopted two approaches to expand the synthetic utility of formic acid derivatives. One is the use of formic acid esters for reactions with alkenes based on the finding that substituted imidazoles can function as the ligands in ruthenium-catalyzed hydroesterifications of alkenes. The other approach involves the use of formic acid derivatives for reactions with (hetero)aryl or alkenyl halides based on the finding that phenyl formate undergoes decomposition to give CO and phenol by simply reacting with a weak base such as triethylamine. In addition to phenyl formate, electrophilic formic acid derivatives such as 2,4,6-trichlorophenyl formate and N-formylsaccharin were found to be stable on storage, but highly reactive, even under ambient reaction conditions, functioning as CO-generating compounds. The in situ generated CO can be incorporated efficiently into products under metal catalysis, thus providing a novel carbonylation. Notably, the carbonylation process did not require the use of external gaseous CO, thus significantly enhancing the safety and practicality of the approach. 1 Introduction 2 Ruthenium-Catalyzed Hydroesterification 3 Palladium-Catalyzed Aryloxycarbonylation 3.1 Decomposition of Phenyl Formate under Weakly Basic Conditions 3.2 Aryloxycarbonylation Using Phenyl Formate 3.3 Room-Temperature Aryloxycarbonylation Using 2,4,6-Trichlorophenyl Formate 4 Reductive Carbonylation Using N-Formylsaccharin 5 Fluorocarbonylation Using N-Formylsaccharin 6 Conclusion

95 citations


Journal ArticleDOI
22 Oct 2014-Synlett
TL;DR: In this article, the authors describe chelation-assisted catalytic transformations of unreactive carbon bonds in aromatic and olefinic compounds, which are achieved by catalytic addition of C-H bonds to alkenes and alkynes, and via coupling reactions such as those of C−H, C−O, C-N, and C−F bonds with boronic esters.
Abstract: Transition-metal-catalyzed functionalization of unreactive carbon bonds such as C–H, C–O, C–N, and C–F bonds has been extensively studied over the last two decades. In this account we describe our studies on chelation-assisted catalytic transformations of unreactive carbon bonds in aromatic and olefinic compounds. Various C–C bond forming reactions are achieved by catalytic addition of C–H bonds to alkenes and alkynes, and via coupling reactions such as those of C–H, C–O, C–N, and C–F bonds with boronic esters. Methods for the conversion of C–H bonds into C–Si and C–X (X = halogen) bonds are also developed. The C–C bond forming reactions are applied to short syntheses of polycyclic aromatic hydrocarbons. 1 Introduction 2 Conversion of C–H Bonds into C–C Bonds 2.1 C–H Alkylation 2.1.1 Scope and Limitations 2.1.2 Mechanistic Studies 2.2 C–H Arylation 2.3 C–H Alkenylation 2.4 Introduction of Carbonyl Functionality via C–H Bond Cleavage 3 Conversion of Aromatic C–O, C–N and C–F Bonds into C–C Bonds by Coupling with Organoboronates 3.1 Coupling with Organoboronates via Aromatic C–O Bond Cleavage 3.2 Coupling with Organoboronates via Aromatic C–N Bond Cleavage 3.3 Coupling with Organoboronates via Aromatic C–F Bond Cleavage 4 Introduction of Heteroatoms at C–H Bonds 4.1 Silylation of C–H Bonds 4.1.1 Silylation of Aromatic C–H Bonds with Hydrosilanes 4.1.2 Silylation of Benzylic C(sp3)–H Bonds with Hydrosilanes 4.1.3 C–H Silylation with Vinylsilanes 4.2 Aromatic C–H Halogenation by Palladium-Catalyzed C–H Bond Cleavage and Electrochemical Oxidation 4.2.1 C–H Chlorination and Bromination 4.2.2 C–H Iodination and One-Pot C–H Iodination/Suzuki–Miyaura Coupling by ON/OFF Switching of Electric Current 5 Applications of C–H Functionalization in Short Syntheses of Polycyclic Aromatic Hydrocarbons (PAHs) 5.1 Convenient Synthesis of Multiarylanthracenes 5.2 Short Synthesis of Alkyl-Substituted Anthracenes and Pentacenes 5.3 Short Synthesis of Dibenzo[a,h]anthracenes and Picenes 6 Conclusions

82 citations


Journal ArticleDOI
31 Jan 2014-Synlett
TL;DR: Ferrocene and ruthenocene-based planar chiral ligands have been developed and used in transition-metal-catalyzed asymmetric allylic substitutions, asymmetric hydrogenations, and asymmetric conjugate addition reactions as mentioned in this paper.
Abstract: Ferrocene- and ruthenocene-based planar chiral ligands have been developed and used in transition-metal-catalyzed asymmetric allylic substitutions, asymmetric hydrogenations, and asymmetric conjugate addition reactions. The most common ferrocene ligands, which have bis(oxazoline) substituents on the cyclopentadiene rings, have been modified to create new planar chiral C 2-symmetric ligands, some of which have shown excellent potential in the aforementioned reactions. A series of planar chiral ruthenocene ligands have also been developed and their activities differ from those of their ferrocene counterparts. 1 Introduction 2 The Design and Synthesis of Planar Chiral Ligands 2.1 Ferrocene-Based Ligands 2.2 Ruthenocene-Based Ligands 3 Applications of Planar Chiral Ligands in Asymmetric Reactions 3.1 Asymmetric Allylic Alkylation 3.2 Asymmetric Allylic Amination 3.3 Asymmetric Allylic Alkylation with Enamines as Nucleophiles 3.4 Asymmetric Alkylation of Aryl Aldehydes 3.5 Asymmetric Hydrogenation 3.6 1,4-Asymmetric Conjugation Reactions 4 Summary

67 citations


Journal ArticleDOI
16 Oct 2014-Synlett
TL;DR: In this article, the authors highlight two recent examples from their group outlining the use of concerted PCET as a platform for the development of catalytic and enantioselective reactions of neutral ketyl radicals.
Abstract: Proton-coupled electron transfers (PCET) are unconventional redox processes in which an electron and proton are exchanged together in a concerted elementary step. While these mechanisms are recognized to play a central role in biological redox catalysis, their applications in synthetic organic chemistry have yet to be widely established. In this Account, we highlight two recent examples from our group outlining the use of concerted PCET as a platform for the development of catalytic and enantioselective reactions of neutral ketyl radicals. Central to this work was the recognition that PCET provides a mechanism for independent proton and electron donors to function jointly as a formal hydrogen atom donor competent to activate organic π systems that are energetically inaccessible using conventional H-atom transfer technologies. In addition, we found that neutral ketyls formed in the PCET event are remarkably strong hydrogen-bond donors and remain strongly associated to the conjugate base of the proton donor following the PCET event. When chiral proton donors are used, these successor H-bond complexes provide a basis for asymmetric induction in subsequent reactions of the ketyl radical. 1 Introduction 2 Concerted PCET and Effective Bond Strengths 3 Concerted PCET Activation of Ketones: A Catalytic Protocol for Ketyl–Olefin Coupling and Mechanistic Investigations 4 Enantioselective PCET Catalysis: Development of Catalytic Asymmetric Aza-pinacol Cyclizations 5 Conclusions

66 citations


Journal ArticleDOI
Daniel Seidel1
27 Jan 2014-Synlett
TL;DR: In this article, the authors describe a dual-catalysis approach and its application to the kinetic resolution of amines and other enantioselective acyl-transfer reactions, which are enabled by the combined action of an achiral 4-(N,N-dimethylamino)pyridine (DMAP) derivative and a chiral anion receptor catalyst.
Abstract: This account details the development of a dual-catalysis approach and its application to the kinetic resolution of amines and other enantioselective acyl-transfer reactions. Anion recognition is an essential design element of these processes, which are enabled by the combined action of an achiral 4-(N,N-dimethylamino)pyridine (DMAP) derivative and a chiral anion receptor catalyst. 1 Introduction 2 Kinetic Resolution of Amines 2.1 Benzylic Amines 2.2 Propargylic Amines 2.3 Allylic Amines 2.4 Benzylic Amines Revisited 2.5 Racemic Diamines 3 Desymmetrization of meso-Diamines 4 Miscellaneous Acyl Transfer Reactions 4.1 Steglich Reaction 4.2 Reactions of Isoquinolines with Azlactones 4.3 Acylation of Silyl Ketene Acetals 5 Conclusions

61 citations


Journal ArticleDOI
06 Nov 2014-Synlett
TL;DR: This work focused on studying the reactivity of enamides and enecarbamates as promising representatives, and gradually developed other cycloaddition reactions and, more generally, an extended range of methods for α,β-difunctionalization.
Abstract: As demonstrated by earlier successes with enamines, nitrogen-activated C=C double bonds have considerable potential for use in the construction of various nitrogen-containing products. To expand the applications of this class of substrates, we focused on studying the reactivity of enamides and enecarbamates as promising representatives. Starting from the well-known Povarov reaction, we gradually developed other cycloaddition reactions and, more generally, an extended range of methods for α,β-difunctionalization. Our most recent work, which involves radical processes, has contributed to a significant increase in the diversity of scaffolds accessible from these nitrogenous substrates and is potentially applicable to various natural and bioactive synthetic targets. 1 Introduction 2 General Design 3 Asymmetric Bronsted Acid-Catalyzed α,β-Difunctionalization of Enamides 3.1 Intramolecular α,β-Difunctionalization of Enamides Through Cycloaddition Reactions 3.1.1 Povarov Reactions 3.1.2 Diels–Alder Reactions of 1-Azadienes 3.2 Intermolecular α,β-Difunctionalization of Enamides 3.2.1 Mannich Reactions 3.2.2 Addition to Azo Compounds 3.2.3 Halogenation Reactions 4 Radical Tandem Difunctionalization: β-Alkylation Followed by α-Functionalization of Enamides 4.1 Photoredox-Mediated Tandem α,β-Difunctionalization of Enamides 4.1.1 Oxyalkylation 4.1.2 Oxy-, Amino- and Carbotrifluoromethylation 4.2 Single-Electron Transfer-Mediated Tandem α,β-Difunctionalization of Enamides 5 Conclusion

61 citations


Journal ArticleDOI
28 Apr 2014-Synlett
TL;DR: In this article, the first example of polymerization of polar vinyl monomers bearing the C=C-C=N functionality by Frustrated Lewis pairs (FLPs) was reported.
Abstract: Reported herein is the first example of polymerization of polar vinyl monomers bearing the C=C–C=N functionality by Frustrated Lewis pairs (FLPs). In particular, FLPs based on Al(C6F5)3 and N-heterocyclic carbenes rapidly convert 2-vinyl pyridine and 2-isopropenyl-2-oxazoline into medium to high molecular weight, N-functionalized vinyl polymers. Activated monomer-alane adduct 1 and initiated zwitterionic intermediate 2 have been isolated and structurally characterized, providing strong evidence for the proposed bimolecular, activated monomer polymerization mechanism.

58 citations


Journal ArticleDOI
21 May 2014-Synlett
TL;DR: In this paper, the results of a recent mechanistic study on unimolecular C-C bond fragmentation (β-scission and O-neophyl rearrangement) and bimolecular hydrogen atom transfer (HAT) reactions of alkoxyl radicals were presented.
Abstract: This account describes the results of our recent mechanistic studies on unimolecular C–C bond fragmentation (β-scission and O-neophyl rearrangement) and bimolecular hydrogen atom transfer (HAT) reactions of alkoxyl radicals. Particular attention is devoted to the study of solvent effects on these reactions by means of time-resolved techniques such as laser flash photolysis. Information is provided on the effect of ring substituents and of the solvent on the spectral properties of arylcarbinyloxyl radicals and on their reactivity in β-scission and O-neophyl rearrangement reactions, showing that a change in solvent can influence the fragmentation reactivity and selectivity. Detailed information has also been obtained on the role of the substrate structure and of the solvent on HAT reactions involving the cumyloxyl radical, showing the importance of solvent hydrogen bond interactions with the substrate and/or the radical on these processes, and providing a general mechanistic description of the kinetic solvent effects observed in HAT reactions from C–H bonds, as well as expanding on the previously available description for HAT from phenolic O–H bonds. The possible application of these findings to synthetically useful C–H functionalization procedures is discussed. 1 Introduction 2 C–C β-Scission Reactions 3 O-Neophyl Rearrangement 4 Hydrogen Atom Transfer (HAT) Reactions 5 Concluding Remarks

57 citations


Journal ArticleDOI
08 May 2014-Synlett
TL;DR: In this paper, a brief review of manganese-catalyzed hydrosilylation is presented along with a personal account of how the design for the highly active catalyst, (Ph2PPrPDI)Mn, was conceived.
Abstract: A brief review of manganese-catalyzed hydrosilylation is presented along with a personal account of how the design for the highly active catalyst, (Ph2PPrPDI)Mn, was conceived. The reductive transformations achieved using this catalyst are described and put into further context by comparing the observed activities with those attained for leading late first-row transition-metal catalysts.

57 citations


Journal ArticleDOI
01 Jun 2014-Synlett
TL;DR: A large variety of halogenated nitroarenes have been selectively reduced with hydrazine hydrate in the presence of Pd/C to give the corresponding (halogenated) anilines in good yield.
Abstract: A large variety of halogenated nitroarenes have been selectively reduced with hydrazine hydrate in the presence of Pd/C to give the corresponding (halogenated) anilines in good yield.

50 citations


Journal ArticleDOI
25 Mar 2014-Synlett
TL;DR: One-pot, three-component condensation of phenols, aromatic aldehydes, and amides in the presence of 3-methyl-1-sulfonic acid imidazolium chloride {[Msim]Cl} as ionic liquid and catalyst under solvent-free condition to prepare a new category of compounds, namely amido-alkyl-phenols has been described in this paper.
Abstract: One-pot, three-component condensation of phenols, aromatic aldehydes, and amides in the presence of 3-methyl-1-sulfonic acid imidazolium chloride {[Msim]Cl} as ionic liquid and catalyst under solvent-free condition to prepare a new category of compounds, namely amido-alkyl-phenols has been described. In the presented work, all products have been reported for the first time.

Journal ArticleDOI
10 Jan 2014-Synlett
TL;DR: An overview of the wide variety of available structures that share the common name "squaraines" with particular attention to the results achieved by our group in the last ten years is given in this paper.
Abstract: The purpose of this account is to give an overview of the wide variety of available structures that share the common name ‘squaraines’, with particular attention to the results achieved by our group in the last ten years. The first section of the report is an introduction and a description of the motivation for our interest in squaraine compounds. The second section includes a survey of the history of squaraines in the scientific literature, and the third section contains a general description of their synthesis and reactivity, together with reports on our direct experiences of their use in materials science, with a focus on squaraines in third-generation photovoltaics, nonlinear optics, and photodynamic therapy. In all of the cases, we highlight the establishment of structure–property relationships directed at the design of materials with improved properties. 1 Introduction and Motivation 2 Squaraines in the Scientific Literature 3 Synthesis of Squaraine Compounds 3.1 Symmetric Derivatives 3.2 Nonsymmetric Derivatives 3.3 Bis-squaraines 3.4 Core-Substituted Squaraines 3.5 Squaraines That We Have Not (Yet) Tried To Make 4 Conclusion

Journal ArticleDOI
10 Jan 2014-Synlett
TL;DR: In this paper, an efficient and novel method for the copper-catalyzed arylation of sulfonamides in water under ligand-free conditions is reported, with high yields, simple workup procedure, and elimination of toxic materials.
Abstract: An efficient and novel method for the copper-catalyzed arylation of sulfonamides in water under ligand-free conditions is reported. The significant advantages of this methodology are high yields, simple workup procedure, and elimination of toxic materials.

Journal ArticleDOI
01 Jan 2014-Synlett
TL;DR: A unique catalyst system comprised of an acridinium photooxidant and a hydrogen atom transfer reagent allows for a range of alkene anti-Markovnikov hydrofunctionalization reactions including hydroalkoxylation, hydroamination, and hydroacetoxylations.
Abstract: The development of a general catalyst system for the ­direct anti-Markovnikov hydrofunctionalization of alkenes is pres­ented. A unique catalyst system comprised of an acridinium photooxidant and a hydrogen atom transfer reagent allows for a range of alkene anti-Markovnikov hydrofunctionalization reactions including hydroalkoxylation, hydroamination, and hydroacetoxylation.

Journal ArticleDOI
27 Mar 2014-Synlett
TL;DR: In this article, the magnetic nanoparticles were recycled six times without any significant loss of catalytic activity, and the catalyst could be recovered simply by using an external magnetic field, which was shown to be useful in the case of E-vinyl boronates.
Abstract: Iron nanoparticles or ferric chloride catalyze the monoborylation of alkynes using bis(pinacolato)diboron to provide E-vinyl boronates with high regio- and stereoselectivity in good to excellent yields. High catalytic activity was observed and the catalyst could be recovered simply by using an external magnetic field. The magnetic nanoparticles were recycled six times without any significant loss of catalytic activity.

Journal ArticleDOI
21 Aug 2014-Synlett
TL;DR: This article highlights recently important developments in the synthesis of difluoromethylated arenes by examining cross-Coupling with Copper, Palladium, and Other Metals.
Abstract: The growing importance of fluorinated compounds in pharmaceuticals, agrochemicals, and materials has triggered the development of new methods for the introduction of fluorine into small molecules. Although it is a challenge to prepare fluorinated compounds, new developed reactions are addressing this challenge and facilitating the synthesis of difluoromethylated arenes. In this article, we highlight recently important developments in the synthesis of difluoromethylated arenes. 1 Introduction 2 Cross-Coupling with Copper 3 Cross-Coupling with Palladium 4 Cross-Coupling with Other Metals 5 C(sp2)–H Activation 6 C(sp3)–H Activation 7 Conclusion

Journal ArticleDOI
11 Apr 2014-Synlett
TL;DR: In this paper, the synthesis and reactions of trifluoromethylated alkynes are described, and the most powerful synthetic intermediates for the preparation of fluorine-containing materials are described.
Abstract: Trifluoromethylated alkynes (CF3 alkynes) are among the most powerful synthetic intermediates for the preparation of ­fluorine-containing materials. In this account, our recent advances on the synthesis and reactions of trifluoromethylated alkynes are described. 1 Introduction 2 Synthesis of Trifluoromethylated Alkynes 3 Addition Reactions of H–M, C–M and M–M (M = Metal) with Trifluoromethylated Alkynes 3.1 Hydrostannation (H–Sn) 3.2 Hydroboration (H–B) 3.3 Hydrosilylation (H–Si) 3.4 Other Hydrometallations (H–Cu, H–Al) 3.5 Carbostannylation (C–Sn) 3.6 Carbocupration (C–Cu) 3.7 Carbopalladation (C–Pd) 3.8 Bisstannylation (Sn–Sn) 3.9 Silylstannylation (Si–Sn) 4 Cyclization Using Trifluoromethylated Alkynes 4.1 Synthesis of Trifluoromethylated Dihydroisoxazoles 4.2 Synthesis of Trifluoromethylated Indoles 4.3 Synthesis of Trifluoromethylated Benzofurans 4.4 Synthesis of Trifluoromethylated Isoquinolines 4.5 Synthesis of Trifluoromethylated Cyclopentenones 4.6 Synthesis of Trifluoromethylated Benzenes 5 Concluding Remarks

Journal ArticleDOI
27 Jan 2014-Synlett
TL;DR: The work in this article summarizes ten years of projects in the Felpin group involving Pd/C as a catalyst for cross-coupling reactions, from early studies to recent developments, the story tells of the successes and the failures, and it shows the progress gained in understanding of factors governing the catalytic activity and efficiency.
Abstract: This account summarizes ten years of projects in the Felpin group involving Pd/C as a catalyst for cross-coupling reactions. From early studies to recent developments, the story tells of the successes and the failures, and it shows the progress gained in understanding of factors governing the catalytic activity and efficiency of Pd/C catalysts. This account could serve as a textbook for synthetic chemists interested in practical methodologies involving C–C bond formation. 1 Introduction 2 Pd/C: Basic Knowledge 3 Early Studies 4 Homemade Pd/C Catalysts 5 Future Prospects 6 Summary and Outlook

Journal ArticleDOI
Jia-Ling Zhang1, Yu Liu1, Ren-Jie Song1, Guo-Fang Jiang1, Jin-Heng Li1 
14 Mar 2014-Synlett
TL;DR: A new visible-light promoted strategy for the difunctionalization of activated alkenes with two C–H bonds has been developed and it is shown that a variety of N-arylacrylamides underwent the 1,2-alkylarylation reaction with acetonitrile or acetone to give the corresponding functionalized oxindoles in moderate to good yields.
Abstract: A new visible-light promoted strategy for the difunctionalization of activated alkenes with two C–H bonds has been developed. In the presence of [Ru(bpy)3Cl2], 4-MeOC6H4N2BF4, Na2CO3 and 36 W compact fluorescent light, a variety of N-arylacrylamides underwent the 1,2-alkylarylation reaction with acetonitrile or acetone to give the corresponding functionalized oxindoles in moderate to good yields.

Journal ArticleDOI
01 Jan 2014-Synlett
TL;DR: In this paper, the first homogeneous catalysts for photochemical C-H borylation with no precious metal catalysts were proposed. But these catalysts do not have the capability of mediating two-electron redox mechanisms and thus require precious metals such as Pd, Ru, Rh, or Ir.
Abstract: Homogeneous catalysts for C–H functionalization typically require precious metals such as Pd, Ru, Rh, or Ir because of their facility in mediating two-electron redox mechanisms. Base metals such as Cu or Fe instead tend to undergo one-electron redox processes. By coupling together two base metal sites in a hetero­bimetallic catalyst design, base metal catalysts for photochemical C–H borylation were discovered. The optimal catalyst, (IPr)Cu–FeCp(CO)2, represents the first homogeneous catalyst for C–H borylation that contains no precious metals. Using metal–metal cooperativity in this way allows for base metal catalysts to replace precious metal catalysts while maintaining advantageous regio­selectivity patterns. The proposed mechanism for heterobimetallic C–H borylation features bimetallic versions of classic organometallic reaction steps, serves as a guide for future catalyst designs, and opens the possibility for other precious metal transformations to be approached using metal–metal cooperativity as a design strategy.

Journal ArticleDOI
17 Dec 2014-Synlett
TL;DR: This account describes the use of phosphines as simple organocatalysts that catalyze the synthesis of complex spirocyclic compounds and their applications, including asymmetric variants and synthetic applications.
Abstract: This account describes the use of phosphines as simple organocatalysts that catalyze the synthesis of complex spirocyclic compounds. Besides our own results, coverage of relevant literature in this field is also provided, including asymmetric variants and synthetic applications. 1 Introduction 2 Cycloaddition Reactions Involving Allenoates or 2-Butynoates 2.1 [3+2] Cycloadditions 2.2 [4+2] Cycloadditions 2.3 [4+1] Cycloadditions 3 [3+2] Cycloadditions with Morita–Baylis–Hillman Adducts 4 Cycloaddition Reactions Using Ynone Derivatives 5 Cycloaddition Reactions Involving Methyl Vinyl Ketone ­ Derivatives 6 Miscellaneous Reactions 7 Conclusions

Journal ArticleDOI
28 Nov 2014-Synlett
TL;DR: In this paper, the second generation of trifluoromethanesulfenamide was used for direct triflomethylthiolation of various aromatic and heteroaromatic compounds, variously substituted.
Abstract: Direct trifluoromethylthiolation of various aromatic and heteroaromatic compounds, variously substituted, can be performed with the second generation of trifluoromethanesulfenamide via a ‘Friedel–Crafts-like reaction’. This reaction requires mild conditions with a catalytic amount of protic or Lewis acid. Good results have been obtained, even with aromatic compounds bearing deactivating substituents.

Journal ArticleDOI
14 Jan 2014-Synlett
TL;DR: In this article, transition metal-free multicomponent reactions involving arynes, N-heterocycles, and various carbonyl compounds have been reported, with (iso)quinoline as the nucleophile and aldehydes, ketones, and N-substituted isatins as electrophiles.
Abstract: Transition-metal-free multicomponent reactions involving arynes, N-heterocycles, and various carbonyl compounds have been reported. With (iso)quinoline as the nucleophile and carbonyl compounds, such as aldehydes, ketones, and N-substituted isatins as electrophiles, the reaction afforded oxazino (iso)quinoline derivatives and the reaction proceeded via 1,4-dipolar intermediates. Interestingly, when the nucleophilic trigger used is pyridine, the reaction furnished indolin-2-one derivatives, and it is probable that the reaction proceeds via a pyridylidene intermediate.

Journal ArticleDOI
24 Mar 2014-Synlett
TL;DR: An efficient synthesis of 2H-indazole derivatives based on the one-pot three-component reaction of 2-chloro- and 2-bromobenzaldehydes, primary amines and sodium azide is described in this paper.
Abstract: An efficient synthesis of 2H-indazole derivatives based on the one-pot three-component reaction of 2-chloro- and 2-bromobenzaldehydes, primary amines and sodium azide is described. The reaction is catalyzed by copper(I) oxide nanoparticles (Cu2O-NP) under ligand-free conditions in polyethylene glycol (PEG 300) as a green solvent.

Journal ArticleDOI
10 Apr 2014-Synlett
TL;DR: In this paper, the authors examine a specific strategy for asymmetric halocyclization reactions, desymmetrizing cyclizations, and highlight recent contributions in this area, highlighting recent contributions.
Abstract: Halocyclization reactions such as halolactonization are powerful synthetic methods for the functionalization of alkenes and alkynes. However, asymmetric versions were thought of as difficult reactions and only recently have new asymmetric, organocatalytic halocyclization methods been reported. Herein, we examine a specific strategy for asymmetric halocyclization reactions, desymmetrizing cyclizations, and highlight recent contributions in this area.

Journal ArticleDOI
28 May 2014-Synlett
TL;DR: Transition-metal-catalyzed C–H activation and C–N bond formation has become one of the most important methods to generate heterocycles through Pd- and Cu-catalystzed intramolecular C(sp3)–H amidation.
Abstract: Transition-metal-catalyzed C–H activation and C–N bond formation has become one of the most important methods to generate heterocycles. Herein, recent progress in the synthesis of functionalized β-lactams through Pd- and Cu-catalyzed intramolecular C(sp3)–H amidation is highlighted.

Journal ArticleDOI
10 Nov 2014-Synlett
TL;DR: An iron-catalyzed hydrogenation of biomass-derived EL to γ-valerolactone (GVL) has been developed using formic acid as hydrogen source.
Abstract: An iron-catalyzed hydrogenation of biomass-derived ethyl levulinate (EL) to γ-valerolactone (GVL) has been developed using formic acid as hydrogen source. Ethyl levulinate was converted into γ-valerolactone quantitatively under optimized reaction conditions. This catalytic process does not require the use of any base or additives.

Journal ArticleDOI
08 Jan 2014-Synlett
TL;DR: Sodium hypochlorite pentahydrate crystals containing less free sodium hydroxide and sodium chloride have been developed as an improved oxidant for secondary alcohols.
Abstract: Sodium hypochlorite pentahydrate crystals containing less free sodium hydroxide and sodium chloride have been developed as an improved oxidant. Primary and secondary alcohols have been oxidized to the corresponding aldehydes and ketones with ­NaOCl·5H2O in the presence of TEMPO/Bu4NHSO4. This new oxidation method does not require pH adjustment and is applicable to sterically hindered secondary alcohols.

Journal ArticleDOI
20 Nov 2014-Synlett
TL;DR: In this paper, a base-promoted ring-opening of siloxydifluorocyclopropanes is presented for a convenient access to cyclic fluoroketones.
Abstract: A convenient access to cyclic fluoroketones that involves base-promoted ring-opening of siloxydifluorocyclopropanes is presented. Selective formation of gem-difluorinated cycloalkanones and monofluorinated enones has been achieved.

Journal ArticleDOI
31 Jan 2014-Synlett
TL;DR: The development of palladium(II)-catalyzed decarboxylative cross-coupling of α-oxocarboxylic acids and their derivatives is summarized in this paper.
Abstract: The development of palladium(II)-catalyzed decarboxylative cross-coupling of α-oxocarboxylic acids and their derivatives is summarized in this account. Acetanilides, 2-phenyl-pyridines, and benzoic acids were found to be suitable substrates for direct acylation through decarboxylative cross-coupling with α-oxo­carboxylic acids. Potassium aryl trifluoroborates were also transformed into ketones, amides, and esters with α-oxocarboxylic acids, oxamic acids, and oxalate monoesters, respectively, in modified catalytic systems. 1 Introduction 2 Palladium-Catalyzed Decarboxylative Cross-Coupling Through C–H Bond Functionalization 2.1 Direct ortho-Acylation of Acetanilides 2.2 Direct Acylation of 2-Phenylpyridines 2.3 Direct ortho-Acylation of Benzoic Acids 3 Transformation of Potassium Aryl Trifluoroborates into Ketones, Esters, and Amides 3.1 Formation of Aryl Ketones from Potassium Aryl Trifluoroborates 3.2 Preparation of Aryl Amides and Esters from Potassium Aryl Trifluoroborates 3.3 Mechanistic Studies 4 Conclusions and Outlook