pinecone/core-2020-05-10-deduplication huggingface dataset:
Microwave-Enhanced Asymmetric Transfer Hydrogenation of N-(tert-Butylsulfinyl)imines

Microwave irradiation has considerably enhanced the efficiency of the asymmetric transfer hydrogenation of N-(tert-butylsulfinyl)imines in isopropyl alcohol catalyzed by a ruthenium complex bearing the achiral ligand 2-amino-2-methylpropan-1-ol. In addition to shortening reaction times for the transfer hydrogenation processes to only 30 min, the amounts of ruthenium catalyst and isopropyl alcohol can be considerably reduced in comparison with our previous procedure assisted by conventional heating, which diminishes the environmental impact of this new protocol. This methodology can be applied to aromatic, heteroaromatic and aliphatic N-(tert-butylsulfinyl)ketimines, leading, after desulfinylation, to the expected primary amines in excellent yields and with enantiomeric excesses of up to 96 %.This work was generously supported by the Spanish Ministerio de Ciencia e Innovación (MICINN) (grant numbers CONSOLIDER INGENIO 2010, CSD2007-00006, CTQ2007-65218 and CTQ2011-24151) and the Generalitat Valenciana (PROMETEO/2009/039 and FEDER). O. P. thanks the Spanish Ministerio de Educación for a predoctoral fellowship (grant number AP-2008-00989)
Diastereoselective Synthesis of Spirocyclic Dihydrofurans and 1-Oxaspiro[4.5]decan-6-one Derivatives from Norbornyl α-Diketones

A diastereoselective zinc-mediated propargylation of non-enolizable norbornyl α-diketones and an efficient AgI-catalyzed cycloisomerization of the resulting α-keto homopropargyl alcohols with terminal alkynes leading to spirocyclic dihydrofurans have been reported. The dihydrofurans obtained were subjected to hydrogenation to afford spiro tetrahydrofuran derivatives in nearly quantitative yields (98-99%). Eventually, the prepared α-spiro tetrahydrofuran norbornyl monoketones were utilized as precursors for acid-mediated Grob-type fragmentation reactions and converted into 1-oxaspiro[4.5]decan-6-one derivatives by treatment with p-toluenesulfonic acid
Cinchona-Derived Picolinamides: Effective Organocatalysts for Stereoselective Imine Hydrosilylation

Picolinamide-cinchona organocatalysts for the successful enantioselective reduction of ketomines were developed. For the first time, a new type of chiral Lewis base, a cationic species, is reported to efficiently organocatalyze the addition of trichlorosilane to imines. Excellent yields with good to high enantioselectivities (up to 91%) were obtained in the reduction of differently substituted substrates. Noteworthy, remarkably high turnover frequencies for the hydrosilylation of imines were observed; the catalyst of choice proved to be active even at a loading of only 1 mol-%. The loading was further reduced to 0.5 mol-%, and for very short reaction times (15 min) very impressive asymmetric catalyst efficiency speed values were reached
Synthesis of [(1,2,3-Triazol-1-yl)methyl]boronic Acids Through Click Chemistry: Easy Access to a Potential Scaffold for Protease Inhibitors

Stereoselective synthesis of previously unreported [(1,2,3-triazol-1-yl)methyl]boronic acids has been achieved from azidomethylboronates by copper-catalyzed azide–alkyne cycloaddition reaction. The proximity of the cycloaddition reaction center to the boronic group is not detrimental to the stability of the sp3 C–B bond or to the stereoisomeric composition, which further expands the field of application of click chemistry to new boronate substrates and offers a new potential scaffold for protease inhibitors
Synthesis, Properties, and Redox Behavior of Tris-(1-azulenyltetracyanobutadiene) and Tris[1-azulenylbis(tetracyanobutadiene)] Chromophores Connected to a 1,3,5-Tri(1-azulenyl)benzene Core

Tris(1-azulenylacetylene) and tris(1-azulenylethynylarylacetylene) chromophores connected to a 1,3,5-tri(1-azulenyl)benzene core have been prepared by the Pd-catalyzed alkynylations of 1-ethynylazulene with tris(3-iodo-1-azulenyl)benzene or iodoarene derivatives substituted with a 1-azulenylethynyl group with tris(3-ethynyl-1-azulenyl)benzene under Sonogashira-Hagihara cross-coupling conditions. These compounds reacted with tetracyanoethylene in formal [2+2] cycloaddition-retroelectrocyclization reactions to afford the corresponding tris(1-azulenyltetracyanobutadiene) and tris[1-azulenylbis(tetracyanobutadiene)] chromophores in excellent yields. The redox behavior of the tetracyanobutadiene (TCBD) derivatives was examined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which revealed their multistep electrochemical reduction properties. Moreover, significant color changes were observed by visible spectroscopy under the electrochemical reduction conditions
Tailor-Made Synthesis of N,N,2,6-Tetrasubstituted 4-Nitroanilines by Three-Component Ring Transformation of Dinitropyridone

The ring transformation of dinitropyridone afforded various kinds of 2,6-disubstituted-4-nitroanilines upon treatment with aliphatic ketones in the presence of ammonium acetate as a nitrogen source, wherein dinitropyridone behaved as the synthetic equivalent of unstable nitromalonaldehyde. The benzene ring, as well as the amino group of the nitroaniline framework, was easily modified by only changing a ketone and the nitrogen source, which afforded N,N,2,6-tetrasubstituted 4-nitroanilines in good to excellent yields
Pyrimidine-Derived Prolinamides as Recoverable Bifunctional Organocatalysts for Enantioselective Inter- and Intramolecular Aldol Reactions under Solvent-Free Conditions

Chiral L-prolinamides 2 containing the (R,R)- and (S,S)-trans-cyclohexane-1,2-diamine scaffold and a 2-pyrimidinyl unit are synthesized and used as general organocatalysts for intermolecular and intramolecular aldol reactions with 1,6-hexanedioic acid as a co-catalyst under solvent-free conditions. The intermolecular reaction between ketone–aldehyde and aldehyde–aldehyde must be performed under wet conditions with catalyst (S,S)-2b at 10 °C, which affords anti-aldols with high regio-, diastereo-, and enantioselectivities. For the Hajos–Parrish–Eder–Sauer–Wiechert reaction, both diastereomers of catalyst 2 give similar results at room temperature in the absence of water to give the corresponding Wieland–Miescher ketone and derivatives. Both types of reactions were scaled up to 1 g, and the organocatalysts were recovered by extractive workup and reused without any appreciable loss in activity. DFT calculations support the stereochemical results of the intermolecular process and the bifunctional role played by the organocatalyst by providing a computational comparison of the H-bonding networks occurring with catalysts 2a and 2b.The Spanish Ministerio de Ciencia e Innovación (MICINN) (projects CTQ2010-20387 and Consolider Ingenio 2010, CSD2007-00006), the Spanish Ministerio de Economia y Competitividad (MINECO) (projects CTQ2013-43446-P and CTQ2014-51912-REDC), Fondos Europeos para el Desarrollo Regional (FEDER), Generalitat Valenciana (PROMETEO 2009/039 and PROMETEOII/2014/017), the Basque Government (GV Grant IT-291-07), the European Commission, FP7 Marie Curie Actions through the ITN ECHONET network (MCITN-2012-316379), the University of Alicante, and the University of the Basque Country are gratefully acknowledged for financial support
Large-scale synthesis of crystalline 1,2,3,4,6,7-hexa-O-acetyl-l-glycero-α-d-manno-heptopyranose.

The higher-carbon sugar l-glycero-d-manno-heptose is a major constituent of the inner core region of the lipopolysaccharide (LPS) of many Gram-negative bacteria. All preparative routes used to date require multiple steps, and scalability has been rarely addressed. Here a highly practical synthesis of crystalline 1,2,3,4,6,7-hexa-O-acetyl-l-glycero-α-d-manno-heptopyranose by a simple four-step sequence starting from l-lyxose is disclosed. Only two recrystallisations are required and the process was demonstrated on a >100 mmol scale, yielding 41 g of the target compound
The Suzuki-Miyaura reaction performed using a palladium-N-Heterocyclic carbene catalyst and a weak inorganic base

We gratefully acknowledge the EC for funding through the seventh framework program SYNFLOW, the ERC (Advanced Investigator Award ‘FUNCAT’ to SPN) and the EPSRC. S.P.N. is a Royal Society Wolfson Research Merit Award holder.N-Heterocyclic carbenes (NHCs) have been shown to be useful ligands for the Suzuki-Miyaura cross-coupling at low catalyst loadings. We now report that the commercially available and air-stable [Pd(IPr)(cin)Cl] pre-catalyst permits the formation of various functionalized biaryls from aryl chlorides and boronic acids (37 examples) under very mild conditions using a mixture of ethanol/water as solvent and an inorganic base.PostprintPeer reviewe
Swivel-cruciform stilbenes based on bithiophene

Bithiophene-based cruciforms with different stilbenoid arms at the 3,3′- and 5,5′-positions have been synthesized by various combinations of Suzuki and Horner–Wadsworth–Emmons (HWE) reactions. According to DFT calculations, the steric hindrance between the arms at the 3,3′-positions produces a twist angle of 57.6° between the two thiophene rings that form the 2,2′-bithiophene unit, an arrangement that leads to a swivel-cruciform structure. The UV/Vis spectra contained strong absorption bands at wavelengths consistent with a twisted molecule with little interaction between the arms. The ability of these compounds to form highly stable radical cations was demonstrated by cyclic voltammetry and this, together with their good solubility in organic solvents, indicates that these materials have potential for the development of solution-processed electronic devices.This research was funded by the Spanish Ministerio de Economía y Competitividad (MINECO) and the European Union (EU) (FEDER project BFU2011-30161-C02-02). The Junta de Comunidades de Castilla-La Mancha (JCCM) is thanked for financial support (FEDER project PEII-2014-005-A) and a doctoral fellowship to A. G.-R.Peer reviewe
Epoxidation of multi-walled carbon nanotubes by organocatalytic oxidation

Even though many functionalization methodologies for covalent modification of carbon nanotubes (CNTs) have been proposed, mild but effective approaches are still needed. Here we describe the epoxidation of multi-walled carbon nanotubes (MWCNTs) with dioxirane for an environmentally friendly oxidation process with an organocatalyst. Thank to the choice of dioxiranes (accessible and easy to handle and to store), multiple oxidation cycles could be performed on the same sample, thus allowing for a final improvement in the degree of oxidation at the CNT sidewall. The obtained derivatives were then used as electrophilic platforms for successive modification with an amine, with a high degree of functionalization (about 750 mu molg(-1) from TGA analysis) being obtained
Remote Substituent Effects on the Stereoselectivity and Organocatalytic Activity of Densely Substituted Unnatural Proline Esters in Aldol Reactions

The organocatalytic activities of highly substituted proline esters obtained through asymmetric [3+2] cycloadditions of azomethine ylides derived from glycine iminoesters have been analyzed by 19F NMR and through kinetic isotope effects. Kinetic rate constants have been determined for unnatural proline esters incorporating different substituents. It has been found that exo-L and endo-L unnatural proline methyl esters yield opposite enantiomers in aldol reactions between cyclic ketones and aromatic aldehydes. The combined results reported in this study show subtle and remote effects that determine the organocatalytic behavior of these synthetic but readily available amino acid derivatives. These data can be used as design criteria for the development of new pyrrolidine-based organocatalysts.Financial support was provided by the Spanish Ministerio de Economía y Competitividad (MINECO) and the Fondo Europeo de Desarrollo Regional (FEDER) (projects CTQ2010-16959/BQU, CTQ2012-35535, CTQ2013-40855-R, CTQ2007-62771/BQU, CTQ2010-20387, CTQ2010-17436, and Consolider-Ingenio CSD2007-00006), the University of the Basque Country (UPV/EHU, UFI11/22 QOSYC), the Basque Government (GV/EJ, grant IT-324-07), the Generalitat Valenciana-FEDER (PROMETEO/2009/039), the Gobierno de Aragón-FSE (research group E40), and the University of Alicante. M. d. G. R. thanks the Donostia International Physics Center (DIPC) for a postdoctoral contract. M. S. and L. C. gratefully thank MINECO for a contract funding their PhD projects
Application of 9-phenyl-fluoren-9-yl Protected Amino Acids in the Synthesis of Tetrahydro-ß-Carbolines

Tetrahydro-ß-carbolines are a prominent group of tricyclic natural products belonging to the indole alkaloids. The large diversity of complex polycyclic compounds in the family coupled with their medicinal properties has made them an extensively studied and extremely attractive target for synthetic organic chemists during the last decades. Reserpine, previously proscribed against hypertension, and tadalafil, a potent PDE5 inhibitor and currently one of the top grossing small molecule pharmaceuticals illustrates the importance of the compound class.
The asymmetric synthesis of tetrahydro-ß-carbolines traditionally relies on a few proven methodologies. The chirality has either been introduced diastereoselectively by substrate controlled reactions, using e.g. chiral auxiliaries, or by external asymmetric induction utilizing e.g. chiral catalysts. Our knowledge and experience on the use of amino acids as starting material in natural product synthesis prompted us to investigate the possibility of transferring the inherent chirality of amino acids to the tetrahydro-ß-carboline scaffold via a chiral pool approach. The use of amino acids as chiral starting material is however hampered by their propensity to undergo racemization/epimerization under certain reaction conditions. To this effect, the 9-phenyl-fluoren-9-yl protecting group was introduced as a means to both protect the amine functionality and at the same time also to protect the vulnerable stereocenter at the alpha-position on the amino acid derivatives.
This thesis aims to provide the reader with a short literature background on the chemistry of tetrahydro-ß-carbolines as well as an overview of different methods available to suppress racemization/epimerization of amino acid derived carbonyl compounds. The thesis will then culminate in the author's own work regarding the synthesis of the tetrahydro-ß-carboline natural products harmicine and eleagnine, by use of a chiral pool approach coupled with a 9-phenyl-fluoren-9-yl protecting group strategy. Herein is furthermore described the synthesis of chiral 2-indolyl methanamines, a structurally closely related group of compounds to the tetrahydro-ß-carbolines largely overlooked in the chemical literature. The thesis will finally end on a discussion regarding the mechanism behind the ability of the 9-phenyl-fluoren-9-yl amine protecting group to retain the stereochemical integrity of amino acid derived carbonyl compounds
Synthesis of Chromen[4,3-b]pyrrolidines by Intramolecular 1,3-Dipolar Cycloadditions of Azomethine Ylides: An Experimental and Computational Assessment of the Origin of Stereocontrol

Azomethine ylides, generated from imine-derived O-cinnamyl or O-crotonyl salicylaldeyde and α-amino acids, undergo intramolecular 1,3-dipolar cycloaddition, leading to chromene[4,3-b]pyrrolidines. Two reaction conditions are used: (a) microwave-assisted heating (200 W, 185 °C) of a neat mixture of reagents, and (b) conventional heating (170 °C) in PEG-400 as solvent. In both cases, a mixture of two epimers at the α-position of the nitrogen atom in the pyrrolidine nucleus was formed through the less energetic endo-approach (B/C ring fusion). In many cases, the formation of the stereoisomer bearing a trans-arrangement into the B/C ring fusion was observed in high proportions. Comprehensive computational and kinetic simulation studies are detailed. An analysis of the stability of transient 1,3-dipoles, followed by an assessment of the intramolecular pathways and kinetics are also reported.Financial support was provided by the Brasilian Universiade Federal do Rio de Janeiro (UFRJ), the Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), by the Spanish Ministerio de Ciencia e Innovación (MICINN) (projects CTQ2010-20387, Consolider Ingenio 2010, CSD2007-00006), the Spanish Ministerio de Economía y Competitividad (MINECO) (projects CTQ2013-43446-P, CTQ2014-51912-REDC, and CTQ2013-45415-P), the Fondos Europeos para el Desarrollo Regional (FEDER), the Generalitat Valenciana (PROMETEO 2009/039 and PROMETEOII/2014/017), the Basque Government (GV/EJ, grant IT-324-07), and the Universities of Alicante and of the Basque Country (UPV/EHU) (UFI11/22 QOSYC)
Functionalization of a Pyridine Framework through Intramolecular Reissert-Henze Reaction of N-(Carbamoyloxy)pyridinium Salts and Unexpected Insertion of Ethereal Solvents

A new strategy for synthesis of the 2-pyridyl carbamates is reported. This strategy exploits a new intramolecular transformation of an acyloxy group from N-carbamoyloxypyridinium salts (Reissert-Henze-type reaction) as the key step. Addition of a silver salt effectively accelerates the intramolecular attack of the carbonyl oxygen at the 2-position of the pyridine ring. Additionally, a new rearrangement of the acyloxy group, combined with insertion of an ethereal solvent to give pyridine derivatives having a coordinating tether, is reported
(E)-2-(4-Arylbut-1-en-3-yn-1-yl)chromones as synthons for the synthesis of xanthone-1,2,3-triazole dyads

Xanthone-1,2,3-triazole dyads have been synthesized by two different approaches, both starting from novel (E)-2-(4-arylbut-1-en-3-yn-1-yl)chromones, prepared through a base-catalyzed aldol reaction of 2-methylchromone and arylpropargyl aldehydes. In the first method, the xanthone moiety is built by Diels-Alder reaction of the referred unsaturated chromones with N-methylmaleimide under microwave irradiation, followed by oxidation of the obtained adducts with DDQ, whereas the 1,2,3-triazole ring results from the cycloaddition reaction of the acetylene moiety with sodium azide. The second strategy first involves the cycloaddition reaction with sodium azide to provide the 1,2,3-triazole ring, followed by methylation of the triazole NH group prior to Diels-Alder reaction with N-methylmaleimide. The last step in this synthesis of novel xanthone-1,2,3-triazole dyads entails oxidation of the cycloadducts with DDQ
Postfunctionalization of the BODIPY Core: Synthesis and Spectroscopy

In this review we describe the various new methodologies for synthetic postmodification of the BODIPY core designed and developed by our research groups, as well as their electronic spectroscopic properties. We discuss the different strategies created for functionalization of the BODIPY framework at the pyrrole C-ring positions and the meso-position. Halogenated boron dipyrrins are substrates for nucleophilic substitution or Pd-catalyzed cross-coupling reactions. α-Unsubstituted BODIPYs can be functionalized with N and C nucleophiles through oxidative or vicarious nucleophilic substitution (VNS) of the α-hydrogen atoms. Combining this methodology with reversible Michael addition onto nitrostyrenes provides a route to 3-styrylated BODIPYs. Furthermore, the one-step, Pd-catalyzed C–H arylation of 3,5-unsubstituted BODIPYs leads to 3- and 3,5-arylated dyes. Finally, radical C–H arylation at the 3,5-positions of α-unsubstituted BODIPYs provides an additional synthesis route to arylated dyes.status: publishe
Reactivity of polar organometallic compounds in unconventional reaction media : challenges and opportunities

Developing new green solvents in designing chemical products and processes or successfully employing the already existing ones is one of the key subjects in green chemistry and is especially important in organometallic chemistry, which is an interdisciplinary field. Can we advantageously also use unconventional reaction media in place of current harsh organic solvents for polar organometallic compounds? This microreview critically analyses the state of the art with regard to this topic and showcases recent developments and breakthroughs that are becoming new research directions in this field. Because metals cover a vast swath of the Periodic Table the content is organised into three sections discussing the reactivity of organometallic compounds of s-, p- and d-block elements in unconventional solvents
Synthesis of 5-/8-Halogenated or Ethynylated Lipophilic Nucleobases as Potential Synthetic Intermediates for Supramolecular Chemistry

This is the peer reviewed version of the following article:  European Journal of Organic Chemistry 2015.32 (2015): 7160-7175, which has been published in final form at http://dx.doi.org/10486/10.1002/ejoc.201501026A series of lipophilic nucleobases that are substituted at the 5- (pyrimidines) or 8- (purines) position with either a halogen atom or a terminal triple bond have been synthesized. The sequences and reactions studied in this work, which mainly comprise halogenation, alkylation, Sonogashira coupling, and trimethylsilylacetylene deprotection, have been carefully optimized, to reach the final compounds in the most straightforward and convenient way, with the highest possible purity and yield. These compounds include cytosine, isocytosine, and uracil derivatives as pyrimidine heterocycles, and guanine, isoguanine, and 2-aminoadenine derivatives as complementary purine bases. Variability was introduced at the N-1/N-9 positions of these pyrimidine/purine nucleobases, which were functionalized with alkyl or benzyl groups, as well as with protected amine or carboxylic acid substituents. The molecules prepared constitute a useful collection of synthetic intermediates for the field of chemical self-assembly. A series of lipophilic nucleobases substituted at the 5- (pyrimidines) or 8-position (purines) with either a halogen atom or a terminal triple bond have been synthesized. These molecules comprise a useful collection of synthetic intermediates for the field of chemical self-assemblyFunding from the European Research Council (ERC-StG 279548) and MINECO (CTQ2011-23659) is gratefully acknowledged. V.V.-G. is grateful for a F.P.I. fellowship from MINECO
One-pot synthesis, crystallization and deracemization of isoindolinones from achiral reactants

The synthesis, crystallization, and complete solid-state deracemization of isoindolinones was realized in one pot simply by grinding achiral reaction components in a suitable solvent with an achiral catalyst. Previously, this concept was applied to a reversible reaction, but herein we showed that it could also be used in combination with reactions in which product formation is irreversible. A controlled final configuration of the product was obtained by using small amounts of chiral additives or seed crystals of the product
Synthetic Studies towards Communesins: Diastereoselective Oxidative Rearrangement of Aurantioclavine Derivatives

Communesins are a class of heptacyclic indole alkaloids that contain two aminal moieties and two contiguous quaternary carbon centers. We have investigated the construction of the pentacyclic skeleton of the communesins by employing the oxidative rearrangement of aurantioclavine derivatives, which are believed to be biosynthetic intermediates of the polycyclic communesin alkaloids. The quaternary C-7 carbon center was constructed in a stereoselective manner, whereas the installation of the C-11 stereocenter requires an epimerization process. The isolation of a 2-ethoxyindolenine prior to the reduction of the nitro group and cyclization steps was critical to the success of this strategy. The pentacyclic skeleton of the communesins has been prepared by the oxidative rearrangement of aurantioclavine derivatives, which are believed to be biosynthetic intermediates of the communesin alkaloids. The quaternary C-7 carbon center was constructed in a stereoselective manner, and the isolation of a 2-ethoxyindolenine intermediate was critical to the success of the strategy