Publications
of the Department of Organic Chemistry
34. |
Multistep Organic Synthesis of Modular Photosystems. Sakai, N.; Matile, S. Beilstein J. Org. Chem., in press. |
33. |
Structure-activity Relationship in the Iridium-catalyzed Isomerization of Primary Allylic Alcohols. Mantilli, L.; Gérard, D.; Besnard, C.; Mazet, C. Eur. J. Inorg. Chem., in press. |
32. |
Synthesis of an Enlarged Library of Dynamic Amphiphilic DNA Activators with Oxime, Disulfide and Hydrazone Bridges. Montenegro, J.; Bang, E.-K.; Sakai, N.; Matile, S. |
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Dynamic amphiphiles have a “bridge” between their charged head and their hydrophobic tails. The presence of dynamic covalent bonds is of interest for differential and biosensing applications as well as for rapid access to the libraries needed to screen for gene delivery or cellular uptake of siRNA. However, efforts to develop libraries have so far concentrated on hydrazone bridges to monocationic heads. Here, we report synthesis efforts to enlarge this focused library with oxime and disulfide bridges and dynamic amphiphiles with more than one positive charge. Evaluation in fluorogenic vesicles reveals best activation of DNA as ion transporters by dynamic amphiphiles with dendritic scaffolds, doubly charged heads and four tails. Moreover, oximes, contrary to hydrazones, remain active under acidic conditions. Linear elongation of dendritic head-groups seems to cause increasing detergent effects and should therefore be avoided. |
31. |
Surprisingly difficult resolution of N-methylated cationic [4]helicenes. Mehanna, N.; Grass, S.; Lacour, J. |
30. |
Enol Acetal Synthesis through Carbenoid C—H Insertion into Tetrahydrofuran Catalyzed by CpRu Complexes. Tortoreto, C.; Achard, T.; Zeghida, W.; Austeri, M.; Guénée, L.; Lacour, J. |
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[CpRu(CH3CN)3][PF6] and diimine ligands catalyze the decomposition of α-diazo-β-ketoesters in THF leading to original products of 1,4-C−H insertion. In contrast with previous results, only novel enol-acetal motifs are obtained through intermolecular C-O instead of C-C bond forming reactions. |
29. |
Copper-catalyzed Asymmetric Conjugate Addition to Challenging Michael Acceptors and Synthesis of Relevant Target Molecules. Gremaud, L.; Palais, L.; Alexakis, A. Chimia 2012, 66, 196-200.
open archive unige:20284
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full text28. |
Tripodal europium complex with triangulenium dye: a model bifunctional metallo-organic system. Hamacek, J.; Besnard, C.; Mehanna, N.; Lacour, J. Dalton Trans. 2012, 41, 6777-6782. open archive unige:20423
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A new tripodal ligand has been designed by coupling pyridyldicarbonyl binding strands with a triazatriangulenium platform (TATA). The complexation reaction with europium provides a C3-symmetrical mononuclear compound that is characterized with NMR, ESMS and qualitatively with single-crystal X-ray crystallography. In addition, photophysical studies of this dual emissive system have been performed, since the combination of the TATA fluorophore with trivalent lanthanides is of potential interest for the further development of imaging applications. |
27. |
Amphiphilic Dynamic NDI and PDI Probes: Imaging Microdomains in Giant Unilamellar Vesicles. Alonso Doval, D.; Fin, A.; Takahashi-Umebayashi, M.; Riezman, H.; Roux, A.; Sakai, N.; Matile, S. |
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Dynamic amphiphiles with fluorescent naphthalenediimide tails can be used to label membrane microdomains and activate DNA as transporters in lipid bilayers.
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26. |
Medium-Sized Rings vs Macrocycles through Rhodium-Catalyzed Ring-Expansion Reactions of Cyclic Acetals. Ballesteros-Garrido, R.; Rix, D.; Besnard, C.; Lacour, J. Chem. Eur. J. 2012, 18, 6626-6631. open archive unige:20422
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α-Diazo β-ketoesters and diketones react with cyclic acetals under Rh(II)-catalysis to yield in one-pot unprecedented polyoxygenated 8- and 9-membered rings. The reactions occur under mild conditions with yields up to 90%. The medium-sized ring formation and perfect regioselectivity are direct consequences of Baldwin’s rules. |
25. |
Copper-Catalyzed Asymmetric 1,4-Addition of Alkenyl Alanes to N-Substituted-2-3-dehydro-4-piperidones. Müller, D.; Alexakis, A. Org. Lett. 2012, 14, 1842-1845. open archive unige:19416
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Readily available vinyl alanes are used in the Cu-catalyzed asymmetric conjugate addition reaction to N-substituted-2-3-dehydro-4-piperidones. The enhanced reactivity of recently developed and easily prepared phosphine amine ligands in combination with inexpensive Cu(II)naphtenate (CuNp) allows the introduction of a great variety of alkenyl, alkyl, and aryl aluminums in high enantioselectivity. |
24. |
Copper-Free Asymmetric Allylic Alkylation Using Grignard Reagents on Bifunctional Allylic Bromides. Grassi, D.; Alexakis, A. Org. Lett. 2012, 14, 1568-1571. open archive unige:18861
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A series of substrates containing a vinylic bromide were employed in a copper-free methodology using bidendate NHC ligands. The desired compounds are generally obtained with good enantioselectivity and good regioselectivity. Importantly the copper-catalyzed system afforded a lower enantioselectivity value. The catalytic products could be transformed into a broad scope of new 1,1-disubstituted olefins in a single step transformation without erosion of the enantioselectivity. |
23. |
Atropoisomeric (P,N) Ligands for the Highly Enantioselective Pd-Catalyzed Intramolecular Asymmetric α-Arylation of α-Branched Aldehydes. Nareddy, P.; Mantilli, L.; Guénée, L.; Mazet, C. Angew. Chem. Int. Ed. 2012, 51, 3826-3831. open archive unige:19419
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A short synthetic route readily gives access to a new class of chiral (P,N) ligands characterized by three distinct elements of chirality. These ligands are highly enantioselective in the challenging Pd-catalyzed intramolecular asymmetric α-arylation of α-branched aldehydes. |
22. |
Self-Organizing Surface-Initiated Polymerization of Perylenediimides on Indium Tin Oxides. Charbonnaz, P.; Sakai, N.; Matile, S. Chem. Sci. 2012, 3, 1492-1496. open archive unige:19403
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In this study, we demonstrate, for the first time, that SOSIP, self-organizing surface-initiated polymerization, a method introduced for facile access to complex surface architectures, is compatible with perylenediimides (PDIs), i.e., established chromophores with very important properties. Highly ordered face-to-face π-stacks are shown to coincide with a more than 100-fold increase of the activity of PDI photosystems, and with significant fill factors. This breakthrough with electron-transporting PDI stacks promises access to powerful combinations with hole-transporting channels. |
21. |
Poly(disulfide)s. Bang, E.-K.; Lista, M.; Sforazzini, G.; Sakai, N.; Matile, S. Chem. Sci. 2012, 3, 1752-1763. open archive unige:20408
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Don't forget poly(disulfide)s. There is a rich literature pointing out the advantages of the dynamic nature of single disulfide bridges to explore self-sorting, biomolecular engineering, biomembrane analysis, and so on. Disulfide bonds between polymer chains are essential for protein folding, materials properties and the stabilization of various supramolecular architectures. However, poly(disulfide)s with disulfide bonds in the main chain are rarely used today to create interesting structures or functions. To attract attention and outline scope and limitations of poly(disulfide)s to build modern supramolecular systems, the rather eclectic recent literature on the topic is summarized. The review is moving from fascinating basic studies including photoinduced metathesis, polycatenanes and polyrotaxanes to applications in biosupramolecular systems such as micelles, membranes, tubes, gels, carriers, pores, sensors, catalysts and photosystems. |
20. |
The Characterization of Synthetic Ion Channels and Pores, 2nd Edition. Matile, S.; Sakai, N. open archive unige:8374 |
19. |
Transport Experiments in Membranes. Matile, S.; Sakai, N.; Hennig, A. open archive unige:18369 |
18. |
Asymmetric C(sp3)-H/C(Ar) Coupling Reactions. Highly enantio-enriched Indolines via Regiodivergent Reaction of a Racemic Mixture. Katayev, D.; Nakanishi, M.; Buergi, T.; Kündig, E. P. Chem. Sci. 2012, 3, 1422-1425. open archive unige:19404
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N-Aryl, N-branched alkyl carbamates react with an in situ generated chiral Pd-NHC catalyst by coupling a Pd-Ar moiety with an aliphatic C-H bond at high temperature to give enantioenriched 2-substituted and 2,3-disubstituted indolines. Prochiral precursors give single products with very high asymmetric induction. Chiral racemic precursors react in a regiodivergent reaction of a racemic mixture to yield enantioenriched indolines resulting from either methyl C-H activation or asymmetric methylene C-H activation. In favorable cases this can result in a complete separation of an enatiomeric mixture into two different highly enantioenriched indolines. |
17. |
Aza-oxindole Synthesis by Oxidative Coupling of Csp2-H and Csp3-H Centers. Dey, C.; Kündig, E. P. Chem. Commun. 2012, 48, 3064-3066. open archive unige:18728
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A CuCl2 mediated oxidative Csp2-H and Csp3-H coupling protocol gives access to aza-oxindoles in good to excellent yield in the presence of NaOtBu as base and toluene as solvent. |
16. |
Excited-state properties of chiral [4]helicene cations. Kel, O.; Sherin, P.; Mehanna, N.; Laleu, B.; Lacour, J.; Vauthey, E. Photochem. Photobiol. Sci. 2012, 11, 623-631. open archive unige:18976
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15. |
Furanoside phosphite–phosphoroamidite and diphosphoroamidite ligands applied to asymmetric Cu-catalyzed allylic substitution reactions. Magre, M.; Mazuela, J.; Diéguez, M.; Pàmies, O.; Alexakis, A. Tetrahedron: Asymmetry 2012, 23, 67-71. open archive unige:18837
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14. |
Enantioselective Self-Sorting on Planar, π-Acidic Surfaces of Anion-π Transporters. Lin, N.-T.; Vargas Jentzsch, A.; Guénée, L.; Neudörfl, J.-M.; Aziz, S.; Berkessel, A.; Orentas, E.; Sakai, N.; Matile, S. Chem. Sci. 2012, 3, 1121-1127. open archive unige:18776
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Self-sorting at interfaces is one of the big challenges we face to prepare the functional organic materials of the future. As a first and decisive step to self-sorting into π-stacks or bundles, we here elaborate self-sorting of π-dimers in solution. Design, synthesis and study of planar naphthalenediimides (NDIs) with one shielded and one free chiral π-surface to direct self-assembly into dimers are described. Stereoisomers are isolated by chiral, preparative HPLC and characterized by X-ray crystallography. NMR studies show that racemates with almost planar, nearly identical π-surfaces prefer uniform self-sorting into homodimers at large differences in π-acidity and alternate self-sorting into heterodimers at small differences in π-acidity. In contrast, enantiomers self-sort "narcissistically" into heterodimers and diastereomers show moderate preference for homodimers. Whereas the lessons learned from dimerization are directly applicable to self-sorting of π-stacks on surfaces, anion transport in lipid bilayers is shown to require a more subtle, somewhat inverse interpretation, with diastereomeric transporters differing dramatically in activity but the least visible supramolecule being confirmed as the best performer. |
13. |
Chiral N-Heterocyclic Carbene Borane Complexes: Synthesis and Structural Analysis. Banerjee, D.; Besnard, C.; Kündig, E. P. Organometallics 2012, 31, 709-715. open archive unige:18164
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A new family of chiral N-heterocyclic carbene borane complexes was synthesized starting from their corresponding imidazolium salts. The complexes were fully characterized. X-ray crystal structures of the complexes were obtained. |
12. |
Mechanistic identification and improvement of a direct enantioconvergent transformation in copper-catalyzed asymmetric allylic alkylation. Langlois, J.-B.; Emery, D.; Mareda, J.; Alexakis, A. Chem. Sci. 2012, 3, 1062-1069. open archive unige:18777
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Recently, our group reported on the development of an unprecedented process in copper-catalyzed Asymmetric Allylic Alkylation. This method allowed for the quantitative transformation of a racemic substrate into an enantioenriched product. While a high level of asymmetric induction (up to 99% ee) was observed, the mechanistic understanding of the reaction remained fuzzy. In the present article, a thorough mechanistic analysis, based on computational investigations, led to the identification of the reaction pathway. Notably, it uncovered that both enantiomers of the starting material converged independently to the same product via two different mechanistic routes. This specific feature established this process as a rare example of Direct Enantioconvergent Transformation. Finally, the modelling results prompted a valuable improvement of the reaction, relying on the use of a more accessible range of substrates. |
11. |
Enyne Chlorides: Substrates for Copper-Catalyzed Asymmetric Allylic Alkylation. Li, H.; Alexakis, A. Angew. Chem. Int. Ed. 2012, 51, 1055-1058. open archive unige:18209
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A select few: Several prochiral enyne chlorides were employed as substrates in the title reaction using Grignard reagents as the alkylation reagents (see scheme; CuTC=copper(I) thiophenecarboxylate). Excellent 1,3 substitution regioselectivities and good to excellent enantioselectivities were obtained. The substrate scope is additionally extended to diene chlorides. |
10. |
Privileged Chiral Ligands and Catalysts (book review). Mazet, C. Angew. Chem. Int. Ed. 2012, 51, 305. open archive unige:18011
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9. |
Asymmetric synthesis of ethano-Tröger bases using CuTC-catalyzed diazo decomposition reactions. Sharma, A.; Besnard, C.; Guénée, L.; Lacour, J. Org. Biomol. Chem. 2012, 10, 966-969. open archive unige:18072
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Nonracemic ethano-bridged Tröger bases are prepared using CuTC-catalyzed decomposition of diazo compounds. Excellent levels of diastereo- and enantio-control (dr and ee up to 12:1 and 95% respectively) are now obtained with aryl diazoketone precursors. |
8. |
Enantioselective Copper-Catalyzed Conjugate Addition of Trimethylaluminium to β,γ-Unsaturated α-Ketoesters. Gremaud, L.; Alexakis, A. Angew. Chem. Int. Ed. 2012, 51, 794-797. open archive unige:18073
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Not a cop out: The copper-catalyzed asymmetric conjugate addition of organometallic reagents to Michael acceptors is an important methodology for forming a C—C bond in an enantioselective manner. Such an addition of Me3Al to β,γ-unsaturated α-ketoesters is described to proceed in high yield and selectivity. CuTC=copper(I) thiophene-2-carboxylate. |
7. |
Clickosomes-Using Triazole-linked Phospholipid Connectors to Fuse Vesicles. Loosli, F.; Alonso Doval, D.; Grassi, D.; Zaffalon, P.-L.; Favarger, F.; Zumbuehl, A. Chem. Commun. 2012, 48, 1604-1606. open archive unige:18071
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Two complementary artificial diether phospholipids were synthesized that can undergo a Cu(I)-catalyzed Huisgen-Sharpless click reaction. The resulting lipid can bridge the membranes of large unilamellar vesicles and cause their aggregation and ultimately their fusion.
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6. |
NMR Experiments for the Analysis of mixtures. Beyond 1D 1H spectra. Furrer, J.; Jeannerat, D. Comb. Chem. High Throughput Screening 2012, 15, 15-35. open archive unige:17549 |
5. |
Chiral anion-based NMR enantiodiscrimination of a dinuclear, cationic Ir(I) NHC complex with a figure-of-eight loop structure. Liu, X.; Lacour, J.; Braunstein, P. Dalton Trans. 2012, 41, 138-142. open archive unige:17761
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A dinuclear Ir(I) complex with a bis-NHC ligand was formed in situ from 1,1’-((4,6-dimethyl-1,3-phenylene)bis(methylene))bis(3-methyl-1H-imidazol-3-ium) in the presence of Cs2CO3 and [Ir(μ-Cl)(cod)]2. Its solid-state structure, determined by X-ray diffraction, shows a figure-of-eight loop with both the P and M enantiomers being present. Solution NMR studies were performed to examine the enantiodiscrimination between them by applying the enantiopure anions tris(tetrachlorobenzenediolato) |
4. |
Electronic effects in 1,3-dipolar cycloaddition reactions of N-alkyl and N-benzyl nitrones with dipolarophiles. Bădoiu, A.; Kündig, E. P. Org. Biomol. Chem. 2012, 10, 114-121. open archive unige:17734
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1,3-Dipolar cycloadditions afforded fast access to isoxazolidines bearing N-alkyl or N-benzyl substituents. The electronic properties of the substituents in the nitrones define the activity of the dipoles and modulate diastereoselectivity in the non-catalyzed reactions. Using a chiral one-point binding ruthenium Lewis acid catalyst, products were obtained in good yields and with excellent regio-, diastereo-, and enantioselectivity. |
3. |
Engineering Antiparallel Charge-Transfer Cascades into Supramolecular n/p-Heterojunction Photosystems: Toward Directional Self-Sorting on Surfaces. Lista, M.; Areephong, J.; Charbonnaz, P.; Orentas, E.; Sakai, N.; Matile, S. Faraday Discuss. 2012, 155, 63-77. open archive unige:18316
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This contribution describes recent progress made with the design, synthesis and evaluation of supramolecular architectures for artificial photosynthesis. Emphasis is on the possible introduction of antiparallel redox gradients into the co-axial hole- and electron-transporting channels of supramolecular n/p-heterojunctions, and on directional, uniform axial and alternate lateral self-sorting to get there. Recent results suggest that two-component gradients in both channels are sufficient for photoinduced charge separation over very long distances. Removal of one gradient leads to charge recombination at the usual critical distances, inversion of both gradients causes photocurrent inhibition. These promising results call for user friendly, cheap and fast approaches to oriented multicomponent architectures on solid surfaces. However, the reduction of efforts devoted to covalent organic synthesis will have to be compensated by the development of strategic concepts on the supramolecular level to tackle basic questions such as self-sorting on surfaces. |
2. |
Copper-catalyzed Enantioselective Allylic Substitution. Langlois, J.-B.; Alexakis, A. open archive unige:17513
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The efficiency of organocopper reagents in the displacement of allylic leaving groups has been well established during the past five decades. In sharp contrast, catalytic asymmetric version of this reaction using a chiral catalyst is a more recent field of research. This chapter presents an overview of tremendous studies towards the development of an “ideally” active catalyst achieving high regio- and enantioselectivities. The comparative reactivity and generality of peptides, phosphorus, as well as N-heterocyclic carbenes based catalysts are discussed in the first part. Then, relevant scope and synthetic applications are reviewed. Noteworthily, this chapter is restricted to C–C bond formation processes, excluding C–B and C–Si bond formations. |
1. |
NASCA‐HMBC, a New NMR Methodology for the Resolution of Severely Overlapping Signals: Application to the Study of Agathisflavone. Bayiha Ba Njock, G.; Bartholomeusz, T. A.; Foroozandeh, M.; Pegnyemb, D. E.; Christen, P.; Jeannerat, D. Phytochem. Anal. 2012, 23, 126-130. open archive unige:18400
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