Search

A family of inherently chiral electroactive selectors based on the 2,2’‐biindole atropisomeric scaffold, of easy synthesis and modulable functional properties, is studied in cascade in two enantioselection contexts. They are at first investigated as probes in enantioselective HPLC, studying molecular structure and temperature effects, and achieving very efficient semipreparative enantioseparation. The enantiomers thus obtained, of remarkable chiroptical features (optical rotation as well as circular dichroism), are successfully applied as selectors in chiral voltammetry in different media for discrimination of the enantiomers of chiral electroactive probes, either by conversion into enantiopure electroactive electrode surfaces by electrooligomerization on glassy carbon substrate (the two monomers with shorter alkyl chains), or as chiral additive in achiral ionic liquid (the monomer with longest alkyl chains). Discrimination is conveniently and reproducibly achieved in terms of significant potential differences for the two enantiomers, specularly inverting either probe or selector configuration. In one case successful discrimination is also observed with the two probe enantiomers concurrently present, either as racemate or with enantiomeric excesses, neatly accounted for by the peak current ratios., A series of inherently chiral electroactive selectors based on the 2,2’‐biindole atropisomeric scaffold is studied in two enantiodiscrimination contests: as probes in enantioselective HPLC and as selectors in chiral voltammetry for successful discrimination of the enantiomers of chiral electroactive probes, either by conversion into enantiopure electroactive electrode surfaces or as chiral additive in achiral ionic liquid.

The novel zinc(II) µ-oxo-bridged-dimeric complex [Zn2(µ-O)2(BMIP)2] (BMIP = 1,3-bis(5-methoxy-1-methyl-1H-indol-3-yl)propane-1,3-dione), 1, was synthetized and fully characterized. The spectral data indicate a zincoxane molecular structure, with the BMIP ligand coordinating in its neutral form via its oxygen atoms. Structural changes in 1 in dimethylsulfoxide (DMSO) were evidenced by means of spectroscopic techniques including infrared absorption and nuclear magnetic resonance, showing DMSO entrance in the coordination sphere of the metal ion. The resulting complex [Zn2(µ-O)2(BMIP)2(DMSO)], 2, readily reacts in the presence of N-methyl-imidazole (NMI), a liquid-phase nucleoside mimic, to form [Zn2(µ-O)2(BMIP)2(NMI)], 3, through DMSO displacement. The three complexes show high thermal stability, demonstrating that 1 has high affinity for hard nucleophiles. Finally, with the aim of probing the suitability of this system as model scaffold for new potential anticancer metallodrugs, the interactions of 1 with calf thymus DNA were investigated in vitro in pseudo-physiological environment through UV-Vis absorption and fluorescence emission spectroscopy, as well as time-resolved fluorescence studies. The latter analyses revealed that [Zn2(µ-O)2(BMIP)2(DMSO)] binds to DNA with high affinity upon DMSO displacement, opening new perspectives for the development of optimized drug substances.

A library of new heterocyclic systems was synthesized starting from oxcarbazepine (OXC, Trileptal®, 10-oxo-10,11-dihydro-5H-dibenzo[b,f]azepine- 5-carboxamide). The key for these transformations is the a-enolizable ketone present on the [d]-side of our starting material OXC, thus, an in depth investigation of the literature to find heteroannulation reactions for substrates carrying an a-enolizable ketone gave us a boost to discover an excellent derivatization strategy and [3+2], [4+2] and [4+1] approaches were successfully developed. Almost always a pre-functionalization was needed, but also the direct one-pot heterocycle construction was also explored. © 2013 by the authors.

A straightforward indole synthesis via annulation of C-nitrosoaromatics with conjugated terminal alkynones was realised achieving a simple, highly regioselective, atom- and step economical access to 3-aroylindoles in moderate to good yields. Further functionalizations of indole scaffolds were investigated and an easy way to JWH-018, a synthetic cannabinoid, was achieved.

Exemestane, a 3rd-generation aromatase inhibitor, is clinically used in the treatment of breast cancer in postmenopausal women. The key step of the industrial synthetic process, i.e., a dehydrogenation to introduce the Δ1-unsaturation, is normally performed with quinones such as p-chloranil or DDQ. We observed the formation of two different hexacyclic by-products, depending on the quinone used in the oxidation step. These compounds arise from an initial [4+2] cycloaddition between the precursor 6-methylenandrost-4-ene-3,17-dione and the quinone reagent, followed by a twofold dehydrohalogenation (with p-chloranil) or dehydrogenation (with DDQ). The structures of these unprecedented hexacyclic adducts were determined by a combination of mass spectrometry, NMR techniques and crystallographic analysis.

An ultrasound-assisted three-component, one-pot domino reaction with ferrocenecarboxaldehyde is herein reported. The sequence of reactions entails the allylindation and dehydrative alkylation of stabilized C-nucleophiles (e.g. electron-rich – (hetero)aromatics and stabilized enols) and N-nucleophiles (e.g. azoles). Sonochemical reactions have been performed in three different high-intensity reactors: a bath (20.3 kHz, 60 W), as well as two cup horns working at 19.9 kHz (75 W) and 300.5 kHz (70 W) giving a library of 18 new ferrocenyl derivatives.

Pyrazoles represent important building blocks for the preparation of bioactive compounds and a large variety of materials, due to their rich coordination chemistry. Unusual and interesting properties may be imparted to molecules embodying highly fluorinated pyrazoles, but to date only few examples of polyfluorinated pyrazoles have been described. In this work we report an improved preparation of 3,5-bis(trifluoromethyl)-1H-pyrazole, the subsequent transformation into hitherto unknown 4-functionalized (F, Cl, Br, I, NO2, NH2) derivatives and the evaluation of selected chemical and physical properties of these compounds.

The gold(I)-catalyzed cycloisomerization of β-allenylhydrazones provides an efficient access to multisubstituted N-aminopyrroles, which are obtained in good to excellent yields. This new intramolecular cyclization method can be applied either to alkyl- or aryl-substituted allenes. The reaction proceeds under mild conditions with short reaction times through a selective intramolecular 1,2-alkyl or -aryl migration extending the general scope of the reaction.

The incorporation of the carbonyl moiety into organic molecules using a three-component matrix, including carbon monoxide, an organic halide, and a nucleophilic component, offers a simple and versatile approach to the formation of carboxylic acids, anhydrides, esters, amides, and ketones. The design of a sustainable synthetic protocol for aminocarbonylation can be efficiently accomplished using a multifaceted strategy that combines solid green catalysts and suitable enabling techniques. The safe and synergistic use of carbon monoxide in a microwave reactor under pressure may be able to create a technological breakthrough in aminocarbonylation reactions. Moreover, a new recyclable catalytic system “CβCAT” based on Pd(II)-triphenylphosphine embedded in cross-linked β-cyclodextrin (hexamethylene diisocyanate) has been found to be very efficient in aryl iodide aminocarbonylation reactions.

3-Aryl-4-hydroxycoumarins have been obtained in satisfactory yields and selectivity through a Rh(II)-mediated arylation of diazocoumarin. The utility of this approach is demonstrated by synthesis of the natural product derrusnin.

The thermal reaction between nitrosoarenes and alkynes under alkylating conditions produces N-alkoxyindoles as the major products in moderate to good yields and excellent regioselectivity. Various electrophiles are used affording different N–O-protected hydroxyindoles in a multi-component fashion. Privileged acetylenic substrates used in reactions with substituted nitrosoarenes are arylalkynes or propiolates. Potentially bioactive compounds and other classes of highly functionalizable indole products were prepared. Reactions between o-carbomethoxy-nitrosoarenes and arylacetylenes provided tricyclic compounds containing an acylaziridine indoline skeleton.

International audience; Novel regioselective ring closing ene-yne metathesis provided an efficient access to different substituted 1-benzazepine scaffolds. The reported synthetic approach could also be used as a powerful tool for the selective formation of a highly functionalizable 2-benzazepine core. This synthetic protocol was even proved to be an efficient way to obtain a functionalizable benzazocine derivative. By modifying the structure of the starting materials, the optimized cyclization finally proved to be a suitable technique to obtain five-and six-membered lactams, enhancing the synthetic application of our method. Five-and six-membered lactams were efficiently prepared by ring-closing metathesis involving the loss of ethylene moiety and affording highly functionalizable compounds showing both electron-withdrawing substituents and electron-donor groups.

The present review is devoted to illustrate the state of the art of the syntheses of indoles, focusing particularly on the most recent developments of new synthetic approaches. Emphasis is given to the preparation of natural products or bioactive compounds containing the indole unit. We present a historical perspective of indole synthesis showing the strategies by choosing the nitrogen precursors. The review is organized sharing the indole synthetic approaches by using different nitrogen-containing functional groups in aromatic substrates used as source of the nitrogen of the indole moiety. Some functional groups and some typical reactions are particularly stressed and highlighted because of the limited coverage given in previous reviews published on this topic. Other synthetic approaches more used and discussed in recent, complete and excellent reviews on the topic are summarized but the most recent published results are highlighted. Our interest is particularly focused on the indolization procedures and on the different methods used for the ring closure and no attention is given to modification of indole structures starting from molecules with a preformed indole unit. Intriguing indole syntheses are continually discovered and the importance that the scientific community gives to these new developments is connected with the strategic role of molecules containing the indole unit. Indoles are the class of heterocycles with more applications and extensive interest due to their biological and pharmacological activity.

The gold(I)-catalyzed cycloisomerization of β-allenylhydrazones provides an efficient access to multisubstituted N-aminopyrroles, which are obtained in good to excellent yields. This new intramolecular cyclization method can be applied either to alkyl- or aryl-substituted allenes. The reaction proceeds under mild conditions with short reaction times through a selective intramolecular 1,2-alkyl or -aryl migration extending the general scope of the reaction.

Meridianins, marine alkaloids known as kinase inhibitors with an indole skeleton, and meridianin analogues were produced regioselectively and in moderate to good yields by thermal annulation of nitrosoarenes with 2-amino-4-ethynylpyrimidine and 2-chloro-4-ethynylpyrimidine, respectively, through a novel and atom-economical indolization process.

We have developed a three-component, one-pot domino reaction that combines the allylindation of 1H-indole-3-carbaldehyde with the dehydrative alkylation of stabilized Cnucleophiles (e.g., electron-rich heteroarenes, electron-rich aromatics, and stabilized enols) or N nucleophiles (e.g., azoles). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Pd-catalyzed homo- and cross-couplings of boronic acids and aryl halides were successfully carried out both in aqueous media under high-intensity ultrasound (US) and in DME under microwave (MW). Heterogeneous catalysis with Pd/C was employed, avoiding phosphine ligands and phase-transfer catalysts. In a trial series involving 15 different iodo- and bromoaryls and 7 boronic acids, both energy sources drastically reduced reaction times affording biaryls in acceptable to good yields. With palladium(II) acetate as catalyst, electron-deficient aryl chlorides also reacted, affording a few biaryls in acceptable yields. Ullmann-type zinc-mediated homocoupling of iodo- and bromoaryls in the presence of Pd/C under CO2 atmosphere was achieved in aqueous media under US, though not under MW. Suzuki homo- and cross-couplings were also carried out in a new reactor developed in our laboratory, featuring combined US and MW irradiation, further improving a green synthetic method.