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1.
Angew Chem Int Ed Engl ; 63(23): e202402481, 2024 Jun 03.
Article in English | MEDLINE | ID: mdl-38529673

ABSTRACT

We report the direct synthesis of new azulene derivatives through gold-catalyzed cyclization reactions. A five-membered ring as backbone in the applied triene-yne substrates turned out to be crucial to induce the 7-endo-dig cyclization mode necessary to trigger azulene formation. The obtained targets are of high interest due to their potential applications in different fields, like organic materials, medicine or cosmetics. UV/Vis spectra and cyclic voltammetry were measured, based on these the electronic properties were determined. Short two or three step sequences towards the applied starting materials make this approach synthetically highly attractive.

2.
Angew Chem Int Ed Engl ; 63(5): e202313738, 2024 Jan 25.
Article in English | MEDLINE | ID: mdl-37882411

ABSTRACT

An efficient, highly selective and divergent synthetic method to construct 2-substituted indoles and aryl-annulated carbazoles via the intermolecular generation of α-imino gold carbenes from terminal alkynes or diynes in combination with sulfilimines is disclosed. Importantly, the tandem reaction is proposed to proceed through an intermolecular gold carbene generation/C-H annulation followed by the activation of a second alkyne leading to 6-endo-dig cyclization, which is significantly different from previous dual activation or 1,6-carbene shift approaches for diyne systems. In the case of ortho-alkynylaniline as starting material, an unexpected regioselective formation of the indole moiety via the intermolecular path, instead of intramolecular hydroamination was discovered. This reactivity paved the way for a one-pot synthesis of the 11H-indolo [3,2-c] quinoline scaffold by exploiting the formed amino indole for a subsequent Pictet-Spengler reaction with aldehydes. The photophysical properties of the carbazoles indicated good violet-blue emission with quantum yields up to 40 %.

3.
Chemistry ; 28(67): e202201424, 2022 Dec 01.
Article in English | MEDLINE | ID: mdl-35996843

ABSTRACT

A novel doubly cyclopentannulated carbazole which is accessible through a successive π-expansion of di(1-naphthylamine) is disclosed. The carbazole moiety is generated in the final step through intramolecular oxidative coupling. The π-expansion of carbazole resulted in strongly altered optoelectronic and electrochemical properties. The solid-state structure features an interesting packing motif with alternating face-to-face π⋅⋅⋅π and edge-to-face C-H⋅⋅⋅π interactions. The experimental findings were corroborated by theoretical calculations.

4.
Chemistry ; 28(34): e202200326, 2022 Jun 15.
Article in English | MEDLINE | ID: mdl-35293646

ABSTRACT

A family of fully bridged triphenylamines with embedded 5- and 7-membered rings is presented. The compounds are potent electron donors capable to undergo donor/acceptor interactions with strong cyano-based acceptors both in the solid state and solution. These interactions were evaluated by IR and UV/vis spectroscopy as well as X-ray crystallography. The vinylene-bridged compound was oxidized to the corresponding 1,2-diketone which readily underwent acid-catalyzed condensation with selected 1,2-phenylenediamines. The resulting π-extended quinoxaline derivatives represent valuable building blocks for the development of functional chromophores upon appropriate functionalization.

5.
Chemistry ; 27(41): 10569-10573, 2021 Jul 21.
Article in English | MEDLINE | ID: mdl-33938059

ABSTRACT

The synthesis of two diazabisacenes is reported. A bisboronated naphthalene was Suzuki-coupled to substituted ethyl nicotinates, then cyclized by intramolecular Friedel-Crafts acylation. The resulting diketones were alkynylated and reduced to give the title compounds, bis(TIPS-ethynyl)-substituted naphtha[1,8-gh:5,4-g'h']diquinoline and naphtho[1,8-bc:5,4-b'c']diacridine. Nitrogen incorporation stabilizes the bisacenes with respect to oxidation compared to their consanguine nonaza analogs.


Subject(s)
Ketones , Acylation , Molecular Structure , Oxidation-Reduction
6.
Chemistry ; 27(36): 9383-9390, 2021 Jun 25.
Article in English | MEDLINE | ID: mdl-33848032

ABSTRACT

One of the most applied reaction types to synthesize shape-persistent organic cage compounds is the imine condensation reaction and it is assumed that the formed cages are thermodynamically controlled products due to the reversibility of the imine condensation. However, most of the synthesized imine cages reported are formed as precipitate from the reaction mixture and therefore rather may be kinetically controlled products. There are even examples in literature, where resulting cages are not soluble at all in common organic solvents to characterize or study their formation by NMR spectroscopy in solution. Here, a triptycene triamine containing three solubilizing n-hexyloxy chains has been used to synthesize soluble congeners of prior insoluble cages. This allowed us to study the formation as well as the reversibility of cage formation in solution by investigating exchange of building blocks between the cages and deuterated derivatives thereof.

7.
Chemistry ; 26(58): 13157-13162, 2020 Oct 15.
Article in English | MEDLINE | ID: mdl-32558004

ABSTRACT

A concise synthetic route towards a new family of phosphorus-containing polycyclic aromatic hydrocarbons starting from the versatile acridophosphine has been established. The structural and optoelectronic properties of these compounds were efficiently modulated through derivatization of the phosphorus center. X-ray crystallographic analysis, UV/Vis spectroscopic, and electrochemical studies supported by DFT calculations identified the considerable potential of these scaffolds for the development of organophosphorus functional materials with tailored properties upon further functionalization.

8.
J Org Chem ; 85(5): 3981-3989, 2020 Mar 06.
Article in English | MEDLINE | ID: mdl-31990546

ABSTRACT

A racemic C3-symmetric trihydroxytribenzotriquinacene was resolved on a large scale by fractional crystallization of the corresponding (1S)-camphanic esters, achieving both enantiopure enantiomers (>99% ee) in 35% and 32% yields. The method relies on a distinct solvent-controlled discrimination process between the diastereomers. The enantiopure trihydroxytribenzotriquinacenes were converted into four other enantiopure building blocks, which are valuable precursors for supramolecular and materials chemistry to illustrate the utility of the synthesized compounds.

9.
Angew Chem Int Ed Engl ; 59(22): 8522-8526, 2020 May 25.
Article in English | MEDLINE | ID: mdl-31972059

ABSTRACT

A novel gold-catalyzed cycloisomerization of 1,6-diynes was achieved, providing an atom-economic approach to a diverse set of bicyclo[2.2.1]hept-5-en-2-ones in moderate to good yields. With unsymmetrical starting materials with two different internal alkynyl substituents, to some extent, the regioselectivity could be controlled by both electronic and steric factors. This unprecedented reactivity pattern may inspire new and unconventional strategies for the preparation of bridged ring systems.

10.
Angew Chem Int Ed Engl ; 59(1): 471-478, 2020 Jan 02.
Article in English | MEDLINE | ID: mdl-31622542

ABSTRACT

We report a switchable synthesis of acylindoles and quinoline derivatives via gold-catalyzed annulations of anthranils and ynamides. α-Imino gold carbenes, generated in situ from anthranils and an N,O-coordinated gold(III) catalyst, undergo electrophilic attack to the aryl π-bond, followed by unexpected and highly selective 1,4- or 1,3-acyl migrations to form 6-acylindoles or 5-acylindoles. With the (2-biphenyl)di-tert-butylphosphine (JohnPhos) ligand, gold(I) carbenes experienced carbene/carbonyl additions to deliver quinoline oxides. Some of these epoxides are valuable substrates for the preparation of 3-hydroxylquinolines, quinolin-3(4H)-ones, and polycyclic compounds via facile in situ rearrangements. The reaction can be efficiently conducted on a gram scale and the obtained products are valuable substrates for preparing other potentially useful compounds. A computational study explained the unexpected selectivities and the dependency of the reaction pathway on the oxidation state and ligands of gold. With gold(III) the barrier for the formation of the strained oxirane ring is too high; whereas with gold(I) this transition state becomes accessible. Furthermore, energetic barriers to migration of the substituents on the intermediate sigma-complexes support the observed substitution pattern in the final product.

11.
Angew Chem Int Ed Engl ; 58(11): 3589-3593, 2019 03 11.
Article in English | MEDLINE | ID: mdl-30600592

ABSTRACT

We herein report the unprecedented synthesis of diverse biologically important aza-heterocycles by employing sulfilimines as nitrene transfer reagents. This class of sulfur-based aza-ylides had not been successfully used for gold nitrene transfer before. This work contains an efficient generation of α-imino gold carbenes by N-S cleavage of sulfilimines. These gold carbenes undergo C-H insertion, cyclopropanation, and nucleophilic attack to form indoles (44 examples), 3-azabicyclo[3.1.0]hexan-2-imines (24 examples), and imidazoles (3 examples). Our study represents a unique gold-catalyzed reaction between alkynes and sulfur ylides, and also includes the first aza-heterocycle synthesis that proceeds by intermolecular nitrene transfer followed by cyclopropanation of the α-imino gold carbenes. Moreover, an unexpected synthesis of 4-acylquinolines (3 examples) from 2-acylphenyl sulfilimines and propargylic silyl ether derivatives by a 1,2-hydride shift onto the α-imino gold carbene and a subsequent Mukaiyama aldol cyclization was discovered.

12.
Beilstein J Org Chem ; 10: 2013-20, 2014.
Article in English | MEDLINE | ID: mdl-25246960

ABSTRACT

Ethynyl[2.2]paracyclophanes are shown to be useful substrates for the preparation of complex, highly unsaturated carbon frameworks. Thus both the pseudo-geminal- 2 and the pseudo-ortho-diethynylcyclophane 4 can be dimerized by Glaser coupling to the respective dimers 9/10 and 11/12. Whereas the former isomer pair could not be separated so far, the latter provided the pure diastereomers after extensive column chromatography/recrystallization. Isomer 11 is chiral and could be separated on a column impregnated with cellulose tris(3,5-dimethylphenyl)carbamate. The bridge-extended cyclophane precursor 18 furnished the ring-enlarged cyclophanes 19 and 20 on Glaser-Hay coupling. Cross-coupling of 4 and the planar building block 1,2-diethynylbenzene (1) yielded the chiral hetero dimer 22 as the main product. An attempt to prepare the biphenylenophane 27 from the triacetylene 24 by CpCo(CO)2-catalyzed cycloisomerization resulted in the formation of the cyclobutadiene Co-complex 26. Besides by their usual spectroscopic and analytical data, the new cyclophanes 11, 12, 19, 20, 22, and 26 were characterized by X-ray structural analysis.

14.
Chem Commun (Camb) ; 47(7): 2059-61, 2011 Feb 21.
Article in English | MEDLINE | ID: mdl-21203628

ABSTRACT

A new chelate phosphine linker and its Pd and Cu complexes have been synthesized and immobilized. The solvent impact on these immobilized species, their mobility, and coordination preferences have been studied in situ by HRMAS (High-Resolution Magic Angle Spinning) NMR. The catalyst recycling characteristics match the HRMAS results.

15.
Chemistry ; 15(20): 5006-11, 2009.
Article in English | MEDLINE | ID: mdl-19360838

ABSTRACT

Mild conditions! Decarbonylative carbonylation by consecutive glyoxylation of indoles, 7-aza-indoles, or pyrroles with oxalyl chloride and subsequent Pd/Cu-catalyzed decarbonylative alkynylation with terminal alkynes furnishes alkynones under very mild conditions. 4-(Indol-3-yl)-, 4-(7-aza-indol-3-yl)-, and 4-(pyrrol-2-yl)-2-amino pyrimidines can be readily obtained in a concise two-step synthesis starting from N-substituted indoles, 7-aza-indoles, or pyrroles (see scheme).

16.
Org Lett ; 10(13): 2797-800, 2008 Jul 03.
Article in English | MEDLINE | ID: mdl-18533671

ABSTRACT

Ortho-phenylene, ethenylene, and ethylene-bridged phenothiazinophanes are synthesized by Suzuki coupling or McMurry dimerization and catalytic hydrogenation at ambient pressure. Intensive intramolecular electronic communication of the phenothiazinyl subunits is found according to cyclic voltammetry. In addition, the macrocycles display blue to green fluorescence with large Stokes shifts. In the solid state, the cyclophanes are arranged in unidimensional stacks. This orientation appears to be favorable for anisotropic charge transport in hole-transport materials for organic field effect transistors (OFET) applications.

17.
Chemistry ; 14(22): 6672-8, 2008.
Article in English | MEDLINE | ID: mdl-18576410

ABSTRACT

Different furans containing an ynamide or alkynyl ether moiety in the side chain were prepared. The gold-catalyzed transformation of these compounds delivered dihydroindole, dihydrobenzofuran, chroman, and tetrahydroquinoline derivatives at room temperature through very fast reactions. Furthermore, the stabilizing effect of the heteroatom directly attached to the intermediate arene oxides led to highly selective reactions, even in the case of only mono-substituted furans, which is quite different from previous results obtained with non-heteroatom-substituted alkynes.

18.
Nucl Med Biol ; 35(4): 413-23, 2008 May.
Article in English | MEDLINE | ID: mdl-18482678

ABSTRACT

Title compounds [3'-sulfonylesters of 2,5'-anhydro-1-(2-deoxy-beta-d-threo-pentofuranosyl)thymine: 2,5'-anhydro-1-(2-deoxy-3-methanesulfonyl-beta-d-threo-pentofuranosyl)thymine (1a); 2,5'-anhydro-1-(2-deoxy-3-(4-nitrobenzenesulfonyl)-beta-d-threo-pentofuranosyl)thymine (1b); 2,5'-anhydro-1(-2-deoxy-3-(toluenesulfonyl)-beta-d-threo-pentofuranosyl)thymine (1c); and 2,5'-anhydro-1(-2-deoxy-3-(2,2,2-trifluoroethanesulfonyl)-beta-d-threo-pentofuranosyl)thymine 1d] were synthesized, and their use as starting materials for the synthesis of 3'-deoxy-3'-[(18)F]fluorothymidine ([(18)F]FLT) was investigated. Radiofluorination of Compound 1b and subsequent hydrolysis with NaOH, in solution or on solid support, yielded a product with the same retention on radio thin-layer chromatography as [(18)F]FLT. However, careful analysis with high-performance liquid chromatography could not identify the product to be [(18)F]FLT. From several options that were investigated to identify the obtained product, it was shown that fluorination had occurred at the nitro group of the nosylate, and not at the 3'-position. Other sulfonate esters (Compounds 1a, 1c and 1d) did not give any fluorination under any of the investigated reaction conditions. It had to be concluded that title compounds are not suitable as starting materials for the synthesis of [(18)F]FLT under the described conditions.


Subject(s)
Dideoxynucleosides/chemistry , Fluorine Radioisotopes/chemistry , Isotope Labeling/methods , Thymidine/analogs & derivatives , Thymidine/chemistry , Alkanesulfonates/chemistry , Anhydrides/chemistry , Molecular Structure , Radiopharmaceuticals/chemical synthesis
19.
J Med Chem ; 51(5): 1260-77, 2008 Mar 13.
Article in English | MEDLINE | ID: mdl-18260613

ABSTRACT

Plasmodium parasites are exposed to higher fluxes of reactive oxygen species and need high activities of intracellular antioxidant systems providing a steady glutathione flux. As a future generation of dual drugs, 18 naphthoquinones and phenols (or their reduced forms) containing three different linkers between the 4-aminoquinoline core and the redox active component were synthesized. Their antimalarial effects have been characterized in parasite assays using chloroquine-sensitive and -resistant strains of Plasmodium, alone or in drug combination, and in the Plasmodium berghei rodent model. In particular, two tertiary amides 34 and 36 showed potent antimalarial activity in the low nanomolar range against CQ-resistant parasites. The ability to compete both for (Fe (III))protoporphyrin and for chloroquine transporter was determined. The data are consistent with the presence of a carrier for uptake of the short chloroquine analogue 2 but not for the potent antimalarial amide 34, suggesting a mode of action distinct from chloroquine mechanism.


Subject(s)
Antimalarials/chemical synthesis , Chloroquine/analogs & derivatives , Chloroquine/chemical synthesis , Glutathione Reductase/antagonists & inhibitors , Naphthalenes/chemical synthesis , Plasmodium falciparum/enzymology , Animals , Antimalarials/pharmacology , Biological Transport , Cell Line, Tumor , Chloroquine/pharmacology , Drug Resistance , Drug Therapy, Combination , Humans , In Vitro Techniques , Malaria/drug therapy , Mice , Mice, Inbred BALB C , Naphthalenes/pharmacology , Parasitic Sensitivity Tests , Plasmodium berghei , Plasmodium falciparum/drug effects , Structure-Activity Relationship
20.
J Org Chem ; 71(9): 3494-500, 2006 Apr 28.
Article in English | MEDLINE | ID: mdl-16626130

ABSTRACT

Annelated 2-amino pyridines such as pyrrolo[2,3-b]pyridines, [1,8]naphthyridines, and pyrido[2,3-b]azepines can be synthesized in moderate to good yields in a consecutive one-pot three-component process by a coupling-isomerization-enamine-addition-cyclocondensation sequence of an electron-poor (hetero)aryl halide, a terminal propargyl N-tosylamine, and an N,S-ketene acetal. After the coupling-isomerization sequence, a Diels-Alder reaction with inverse electron demand of the intermediate enimine and the N,S-ketene acetal and subsequent aromatization furnish annelated 2-amino pyridines 4 that were unambiguously characterized by numerous X-ray structure analyses. These heterocycles are highly fluorescent and partially pH sensitive, and their electronic structure was studied with spectroscopic and computational methods.

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