A5029216204- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- Synthesis and Properties of Aromatic Compounds
- Molecular spectroscopy and chirality
- Cyclization and Aryne Chemistry
- Synthetic Organic Chemistry Methods
- DNA and Nucleic Acid Chemistry
- Axial and Atropisomeric Chirality Synthesis
- Catalytic C–H Functionalization Methods
- Photochromic and Fluorescence Chemistry
- Catalytic Alkyne Reactions
- Crystallography and molecular interactions
- Porphyrin and Phthalocyanine Chemistry
- Catalytic Cross-Coupling Reactions
- Cyclopropane Reaction Mechanisms
- Asymmetric Synthesis and Catalysis
- Analytical Chemistry and Chromatography
- Microfluidic and Capillary Electrophoresis Applications
- Molecular Sensors and Ion Detection
- Advanced biosensing and bioanalysis techniques
- Radical Photochemical Reactions
- RNA Interference and Gene Delivery
- Photoreceptor and optogenetics research
- Origins and Evolution of Life
- Oxidative Organic Chemistry Reactions
Czech Academy of Sciences, Institute of Organic Chemistry and Biochemistry
2014-2024
General University Hospital in Prague
2022
Charles University
2003-2022
University of Cambridge
2022
Czech Academy of Sciences
1999-2017
New York University Abu Dhabi
2015
University of Chemistry and Technology, Prague
2012
University of Glasgow
2003-2008
Max-Planck-Institut für Kohlenforschung
2006-2007
Max Planck Institute of Molecular Physiology
2007
Reactions triggered by light constitute a treasure trove of unique synthetic methods that are available to chemists. Photoinduced redox processes using visible in conjunction with sensitizing dyes offer great variety catalytic transformations useful the realm organic synthesis. The recent literature amply shows this preparative toolbox is expanding substantially. This review discusses historical and contemporary work area photoredox catalysis [Ru(bpy) 3 ] 2+ . Elegant examples from most...
The taming of the screw: CoI-catalyzed cyclotrimerization triynes and microwave (MW) assisted aromatization with MnO2 are central to practical synthesis diaza[5]helicene aza[6]helicenes. aza[6]helicene racemates have been resolved, absolute configuration enantiomers assigned, energy barriers racemization determined, X-ray structures their Ag complexes obtained (see picture; Cp=C5H5, OTf=triflate). Supporting information for this article is available on WWW under...
A concise and convergent total synthesis of the highly cytotoxic marine natural products iejimalide A−D (1−4) is reported, which relies on an effective ring-closing metathesis (RCM) reaction a cyclization precursor containing no less than 10 double bonds. Because exceptional sensitivity this polyunsaturated intermediate its immediate precursors toward acid, base, even gentle warming, assembly process hinged upon judicious choice protecting groups careful optimization all individual...
An original approach to helicene frameworks exploiting atom economic isomerization of appropriate energy-rich aromatic cis,cis-dienetriynes has been developed. The new paradigm provides nonphotochemical syntheses helicenes based on the easy, convergent, and modular assembly key their nickel(0)-catalyzed [2+2+2] cycloisomerization. potential methodology is underlined by parent [5]helicene (2), 7,8-dibutyl[5]helicene (23), [6]helicene (24), [7]helicene (25). can be adapted prepare...
A nonphotochemical synthetic route to 3-hexahelicenol is reported. It involves a key [2+2+2] cycloisomerization of CH(3)O-substituted triyne that readily available from 1-methoxy-3-methylbenzene and 1-bromo-2-(bromomethyl)naphthalene. Further functional group transformations led 3-CO(2)CH(3), 3-NH(2), 3-PPh(2), 3-SC(O)N(CH(3))(2) substituted hexahelicenes.
A series of modular bipyridine-type ligands 1 and 3-9 has been synthesized via a de novo construction the pyridine nucleus. The chiral moieties these originate from isoprenoid pool, namely, beta-pinene (10 --> 1), 3-carene (14 3 5), 2-carene (28 4), alpha-pinene (43 6-8), dehydropregnenolone acetate (48 9), respectively. Copper(I) complexes, derived (TfO)(2)Cu (1 mol %) upon an in situ reduction with phenylhydrazine, exhibit good enantioselectivity (up to 82% ee) unusually high reaction rate...
As easy as one, two, three: Relying on a facile [2+2+2]-cycloisomerization strategy, we have developed robust three-step synthetic entry into novel family of helical extended diquats (helquats). The key metal-catalyzed step proceeds in water under aerobic conditions to produce water-soluble, blue fluorophore (picture; TfO=triflate). electrochemical manifold the parent helquat features two reversible one-electron reduction steps. Detailed facts importance specialist readers are published...
Two-step redox switching in enantiopure helquat system [P-1](2+) ⇌ [P-1](•+) [P-1](0) is demonstrated. The viologen-type electroactive unit embedded directly the helical scaffold of 1 responsible for prominent chiroptical at 264 nm. This process associated with a marked sign-reversal Cotton effect ramping between Δε = +35 M(-1) cm(-1) and -100 [P-1](0). helically chiral features most intense switch response documented field helicenoids.
Helquat dyes combine a cationic hemicyanine with helicene-like motif to form new blueprint for chiral systems large and tunable nonlinear optical (NLO) properties. We report series of such species characterization, including determination static first hyperpolarizabilities β0 via hyper-Rayleigh scattering Stark spectroscopy. The measured values are similar or substantially larger than that the commercial chromophore E-4′-(dimethylamino)-N-methyl-4-stilbazolium. Density functional theory...
Diastereoselective CoI-mediated [2 + 2 2] cycloisomerization of CH(3)O-substituted optically pure aromatic triynes to obtain nonracemic functionalized helicene-like compounds (comprising a penta-, hexa-, and heptacyclic helical scaffold) was studied. The stereochemical outcome the reaction at 140 degrees C using CpCo(CO)(2) controlled by thermodynamic factors yielding diastereomeric ratios up 91:9. Using CpCo(ethylene)(2) room temperature, kinetic control took place leading loss...
A straightforward synthetic approach to a new class of molecules with helical chirality has been developed involving an intramolecular [2 + 2 2] cycloisomerization triynes under CpCo(CO)2/PPh3 catalysis. The cyclization reaction is promoted by visible light irradiation. Starting from 1,2-diarylacetylenes two terminal or methyl-substituted tethered acetylene moieties (1a,b, 4, 5, and 7), the target products (8a,b, 11, 12, 14) are obtained in 64−89% yield. bearing trimethylsilyl groups (1c, 2,...
[reaction: see text] A new approach to nonracemic [7]helicene-like molecules has been developed. Stereoselective Co(I)-mediated [2 + 2 2] cycloisomerization of aromatic triynes containing an asymmetric carbon atom produces scaffolds in diastereomeric ratios up 100:0. This central-to-helical chirality transfer can be controlled by the absolute configuration at center and presence substituents.
Silberschrauben: Eine Cobalt(I)-katalysierte Triin-Cyclotrimerisierung mit anschließender Aromatisierung durch MnO2 unter Mikrowellenbestrahlung schließt eine praktische Synthese von Diaza[5]helicenen und Aza[6]helicenen ab. Die Aza[6]helicen-Enantiomere wurden getrennt, die Energiebarriere für Racemisierung bestimmt Röntgenstrukturanalysen an Silberkomplexen ausgeführt (siehe Bild; Cp = C5H5, OTf Triflat).
Helically chiral styryl dyes with large ECD in the visible region are introduced.
Metathesis to the rescue: Although counterintuitive at first sight, application of ring-closing metathesis (RCM) a cyclization precursor containing 10 double bonds has led selective and high-yielding formation macrocyclic core iejimalide B, potent cytotoxic agent marine origin. In contrast, macrolactonization approach failed afford this intricate target.
Abstract Enantiomers of helical N‐heteroaromatic dications, helquats, were separated by CE. An acidic 22/35 mM sodium/phosphate background electrolyte, pH 2.4, with addition randomly sulfated α‐, β‐ and γ‐ cyclodextrins allowed enantioresolution a series which comprised 5, 6 7 fused rings participating in the backbone. In general, at least one chiral selectors was found to provide baseline separation for 22 out 24 helquats partial remaining two. Individually, γ‐cyclodextrin turned separate...
Electrochemical reduction of an azoniahelicene affords a dimer, accompanied by strong change in the electronic circular dichroism. The fast dimerisation event leads to >500 mV shift oxidation potential, affording large area bistability, where chiroptical signal only depends on redox history.
Limitations of models in total synthesis are illustrated by a study towards the potent cytotoxic macrolide iejimalide B. Although Yamaguchi protocol allowed for esterification elaborate segments, attempted macrolactonization seco acid met with failure (see scheme, Boc= tert-butyloxycarbonyl). The assembly involves some most advanced applications Julia olefination known to date.
A dicationic [6]helicene congener captured on the racemization pathway in its saddle-shaped geometry is introduced. Synthesis, structure, resolution, and dynamic properties of this chiral [6]saddlequat in-between highly stereocontrolled transformation into enantiopure [6]helquat are discussed demonstrated. The aspects established by experiment supported detailed DFT-D calculations presented visually form a movie (electronic table-of-contents electronic supplementary information). title was...
Abstract The bistriflate salt of racemic [5]helquat 1 was found to form a conglomerate. Based on this finding, the preferential crystallization chiral helicene–viologen hybrid developed deliver pure enantiomers 20 g scale (10.5 each enantiomer). To best our knowledge, is largest amount nonracemic helicene‐like compound obtained by date. absolute configuration P enantiomer confirmed X‐ray crystal structure analysis. chromatography‐free synthesis multigram (30 g) also presented as an entry...
Chirality induction phenomena attract attention because of their relevance to intermolecular interactions encountered in living matter. Usually, such effects are weak. However, enantiomers a [6]helquat dye were found induce exceptionally strong chirality several achiral solvents containing nitrile groups. This effect was observable as an intense Raman optical activity (ROA) induced acetonitrile, acetonitrile-d3, and liquid hydrogen cyanide solvents. The observation verified by measurement...
Abstract Asymmetric synthesis of helicenes and their congeners has been demonstrated to rely either on enantioselective Ni 0 /PR 3 * -catalyzed [2+2+2] cycloisomerization triynes or diastereoselective Co I chiral triynes. The former approach providing tetrahydrohelicenes in a nonracemic form requires further development as moderate enantioselectivities (up 54 % ee) have so far achieved under kinetic control. latter affording helicene-like structures diastereomerically enriched allows for...