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1.
J Org Chem ; 2020 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-32907321

RESUMO

A straightforward approach to the synthesis of two different series of cationic [5]helicenes has been achieved including, in dioxa series, the possibility to introduce aromatic functional groups at the periphery of the helical structure. While photophysical study highlights that the introduction of aryl substituents at position 23 of the helical moieties has a negligible impact on the optical properties, styryl substituents allow a welcoming extension of the conjugation pathways. Finally, a red shift of the optical properties was evidenced upon introduction of nitrogen atoms in the helicene scaffold, leading to particularly good fluorescence efficiencies in the red domain for a helicenic dye. Detailed information on racemization kinetics was collected for the most stable species upon direct high-performance liquid chromatography (HPLC) resolution or, when configurational lability was too high, through VT-HPLC analysis on the chiral stationary phase (ΔG‡ values ranging from 85.0 to 137.1 kJ·mol-1 and above).

2.
Chem Commun (Camb) ; 56(68): 9771-9774, 2020 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-32728683

RESUMO

A series of water-soluble helicene dyes generating intense electrochemiluminescence (ECL) signal in physiological conditions is reported. Those species were prepared using diaza [4] and [6]helicenes as structural cores modified with sulfonate groups in various positions. Such groups improve their water solubility and can induce a red-shifted emission. Efficient ECL up to the near-infrared is achieved in water, demonstrating a viable strategy for the design of new near-infrared ECL dyes for bioassays and microscopy.

3.
Chem Commun (Camb) ; 56(44): 5989-5992, 2020 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-32347858

RESUMO

We demonstrate the possibility to detect selectively the two single enantiomers of a model [Ru(bpy)3]2+-based dye by circularly polarized-electrochemiluminescence (CP-ECL). This new aspect of the ECL emission combines the chiral information intrinsic to CPL methods with an electrogeneration of the excited state. Thus, it opens the possibility to perform ECL-based bioassays or microscopy with efficient chiral dyes.

4.
Org Biomol Chem ; 18(2): 250-254, 2020 01 02.
Artigo em Inglês | MEDLINE | ID: mdl-31808765

RESUMO

Double hydrothiolation of bis enol ether macrocycles was achieved under photo-mediated conditions. The thiol-ene reactions afford a fully regioselective anti-Markovnikov post-functionalization. Thanks to the use of ethanedithiol as reagent, moderate to excellent diastereoselectivity was accomplished leading to macrocycles containing four defined stereocenters in only three steps from 1,4-dioxane, tetrahydrofuran (THF) or tetrahydropyran (THP).

5.
Chirality ; 32(2): 139-146, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31847051

RESUMO

Verkade's superbases, entrapped in the cavity of enantiopure hemicryptophane cages, have been synthesized with enantiomeric excess (ee) superior to 98%. Their absolute configuration has been determined by using electronic circular dichroism (ECD) spectroscopy. These enantiopure encaged superbases turned out to be efficient chiral derivatizing agents for chiral azides, underlining that the chirality of the cycloveratrylene (CTV) macrocycle induces different magnetic and chemical environments around the phosphazide functions.

6.
Chem Sci ; 10(29): 7059-7067, 2019 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-31588273

RESUMO

Oxygen atoms of cationic dioxa and azaoxa [6]helicenes can be exchanged by amino groups to form azaoxa and diaza [6]helicenes respectively. The mild reaction conditions developed herein allow the construction of libraries of derivatives with sensitive and/or functionalized side chains. Using enantioenriched dioxa or azaoxa helicene precursors, these exchanges lead to either near racemization (es 3%) or to a remarkable enantiospecificity (es up to 97%). This unusual behavior is fully characterized via experimental and computational mechanistic evidence. Based on these investigations, the enantiospecificity of the first transformation can be improved to 57-61%.

8.
Org Biomol Chem ; 17(28): 6905-6910, 2019 07 17.
Artigo em Inglês | MEDLINE | ID: mdl-31270519

RESUMO

The stereoselective synthesis of chiral macrocycles bearing two aliphatic amide functional groups is reported. After the amidation mediated by TBD, a guanidine derivative, the olefin transposition step is performed with a slight excess of t-BuOK. The products are afforded in moderate to good combined yields (up to 59%) and with an excellent syn diastereoselectivity (dr > 49 : 1). Introducing enantiopure α-branched substituents was possible and it resulted in mixtures of diastereomers, which could be tested as phase-transfer catalysts using the formation of a phenylalanine analog as a test reaction (up to 43% ee). A clear matched-mismatched situation was observed in the two diastereomeric series.

10.
Angew Chem Int Ed Engl ; 58(21): 6952-6956, 2019 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-30916870

RESUMO

The first observation of circular polarization of electrochemiluminescence (ECL) from a purely organic derivative is reported. A bispyrene scaffold mounted on a constrained polyether macrocycle displaying intense excimer fluorescence and highly circularly-polarized (CP) photoluminescence has been selected for this purpose. The compound displays an ECL dissymmetry factor of about |8×10-3 |, which is in good agreement with the corresponding photoluminescence value. This observation is the first step towards the molecular engineering of tailored dyes that can act as both ECL and CP-ECL reporters for (bio)analysis by bringing a new level of information when dealing with chiral environments. Additionally, it provides an extra dimension to the ECL phenomenon and opens the way to chiral detection and discrimination.

11.
Org Lett ; 21(3): 687-691, 2019 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-30657690

RESUMO

Selective formation of oxonium ylides from morpholines and α-diazo-ß-ketoesters was achieved. This was applied to the high-concentration (0.5 M) dirhodium-catalyzed (0.1 mol %) [3 + 6 + 3 + 6] synthesis of 18-membered ring diaza macrocycles (46%-72%). Late-stage functionalization of these derivatives is demonstrated. Mechanistic evidence for a novel (undesired) diazo decomposition pathway is also reported.

12.
Chem Sci ; 9(35): 7043-7052, 2018 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-30310624

RESUMO

Straightforward synthesis and resolution of a series of chiral fluorescent macrocycles are presented, together with their electronic circular dichroism (ECD), strong excimer fluorescence (EF, λ 300 to 650 nm) and allied highly circularly polarized luminescence (CPL, g lum up to 1.7 × 10-2). The ECD, EF and CPL responses are strongly affected by the presence of metal ions (Na+, Ba2+) thanks to deep conformational changes. While ECD signals can be almost completely reversibly inverted upon the complexation/decomplexation of metal ions in a typical binary response, CPL signals are reversibly quenched concomitantly. The designed macrocycles display thus a remarkable combination of both +/- ECD and on/off CPL reversible switching.

13.
Chemistry ; 2018 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-29698563

RESUMO

A series of nine C-functionalized cationic diazaoxatriangulene (DAOTA) dyes have been successfully synthesized and fully characterized, including X-ray structural analysis of four derivatives. The introduction of electron-withdrawing or -donating functions enables the tuning of both electro- and photochemical properties with, for instance, two consecutive (reversible) reductions or oxidations observed for nitro or amino derivatives, respectively. The substituents also impacted on the optical properties, with absorption maxima varying from λ=528 to 640 nm and fluorescence being shifted from the yellow to the red range, up to λ=656 nm.

14.
Angew Chem Int Ed Engl ; 57(24): 7151-7155, 2018 06 11.
Artigo em Inglês | MEDLINE | ID: mdl-29673027

RESUMO

Polycyclic indoline-benzodiazepines can be accessed through the intermolecular reaction of Tröger bases with N-sulfonyl-1,2,3-triazoles. Under RhII catalysis, α-imino carbenes are generated and a subsequent cascade of [1,2]-Stevens, Friedel-Crafts, Grob, and aminal formation reactions yield the polycyclic heterocycles as single isomers (d.r.>49:1, four stereocenters including two bridgehead N atoms). Further ring expansion by insertion of a second α-imino carbene leads to elaborated polycyclic 9-membered-ring triazonanes.


Assuntos
Benzodiazepinas/síntese química , Indóis/síntese química , Compostos Policíclicos/síntese química , Benzodiazepinas/química , Catálise , Iminas/química , Indóis/química , Metano/análogos & derivados , Metano/química , Modelos Moleculares , Compostos Policíclicos/química , Ródio/química , Estereoisomerismo , Triazóis/química
15.
Org Biomol Chem ; 16(6): 919-923, 2018 02 07.
Artigo em Inglês | MEDLINE | ID: mdl-29334105

RESUMO

Twelve cationic helicenes and one triangulene were tested for the specific labeling of mitochondria from algal cells. Octyl ester derivative 5 readily penetrates algal cells and gives rise to clear fluorescence patterns when it is used at concentrations in the µM range. Under these conditions, cell structures are well preserved and cell survival is not compromised. Cationic helicene compounds such as 5 provide new useful tools for examining the mitochondrial network and its dynamics including fission and fusion events.


Assuntos
Chlamydomonas/metabolismo , Corantes Fluorescentes/química , Mitocôndrias/metabolismo , Compostos Policíclicos/química , Sobrevivência Celular/efeitos dos fármacos , Fluorescência , Corantes Fluorescentes/síntese química , Microscopia Confocal , Compostos Policíclicos/síntese química
16.
Chemistry ; 24(12): 2944-2951, 2018 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-29314316

RESUMO

Following a late-stage functionalization strategy, a series of heteroditopic cryptand receptors were prepared in three steps only from 1,4-dioxane. As evidenced by 1 H NMR spectroscopic and solid state analyses, these polyamide-crown ether conjugates present general ion pair binding capacity towards salts of monovalent cations and linear triatomic anions.

17.
Chem Sci ; 8(8): 5713-5720, 2017 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-28989611

RESUMO

Using N-sulfonyl triazoles as substrates, compounds as diverse as 2-imino tetrahydrofurans, 13- and 15-membered ring aza-macrocycles can be prepared selectively via formal [1 + 4], [5 + 4 + 4] and [3 + 4 + 4 + 4] condensations of α-imino carbenes and oxetanes under Rh(ii)-catalysis or thermal activation. Spirocyclic N-heterocycles are also accessible by means of Buchwald-Hartwig and Pictet-Spengler cyclizations. By reaction control, substrate selection or further derivatization, a large variety of chemical structures is thus achievable. Finally, using triazoles reacting under thermal activation, interesting mechanistic insight was obtained.

18.
Chemistry ; 23(55): 13596-13601, 2017 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-28766311

RESUMO

A strategy for late-stage electrophilic functionalizations of cationic helicenes is exposed. Thanks to strongly acidic conditions that permit reversible electrophilic substitutions, regioselective acylations, sulfonylations, or alkylations occur at the extremity(ies) of the helical cores. Extended [5] or [6]helicenes can then be generated from cationic [4]helicenes in successive one-pot elongation processes. Retention of configuration and excellent enantiospecificity (up to 99 %) are observed for the helicene growth in the enantiopure series.

19.
Chemistry ; 23(36): 8678-8684, 2017 Jun 27.
Artigo em Inglês | MEDLINE | ID: mdl-28406541

RESUMO

In the context of Tröger base chemistry, regio- and stereoselective Csp3 -H azidation reactions are reported. Azide functional groups are introduced at either one or the two benzylic positions selectively. Mild conditions and good yields are afforded by the combination of TMSN3 and iodosobenzene PhIO. The process occurs with high enantiospecificity (es 96-99 %) and-interestingly and importantly-via bridgehead iminium intermediates as shown by mechanistic and in-silico studies. Finally, mono- and bistriazole derivatives were prepared in high yields and enantiospecificity by using copper-catalyzed alkyne azide cycloaddition (CuAAC) reactions; some of the products were used as anion-binding organocatalysts for the tritylation of amines and alcohols.

20.
Chemistry ; 22(51): 18394-18403, 2016 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-27885721

RESUMO

The physicochemical properties of cationic dioxa (1), azaoxa (2), and diaza (3) [6]helicenes demonstrate a much higher chemical stability of the diaza adduct 3 (pKR+ =20.4, Ered1/2 =-0.72 V) compared to its azaoxa 2 (pKR+ =15.2, Ered1/2 =-0.45 V) and dioxa 1 (pKR+ =8.8, Ered1/2 =-0.12 V) analogues. The fluorescence of these cationic chromophores is established, and ranges from the orange to the far-red regions. From 1 to 3, a bathochromic shift of the lowest energy transitions (up to 614 nm in acetonitrile) and an enhancement of the fluorescence quantum yields and lifetimes (up to 31 % and 9.8 ns, respectively, at 658 nm) are observed. The triplet quantum yields and circularly polarized luminescence are also reported. Finally, fine tuning of the optical properties of the diaza [6]helicene core is achieved through selective and orthogonal post-functionalization reactions (12 examples, compounds 4-15). The electronic absorption is modulated from the orange to the far-red spectral range (560-731 nm), and fluorescence is observed from 591 to 755 nm with enhanced quantum efficiency up to 70 % (619 nm). The influence of the peripheral auxochrome substituents is rationalized by first-principles calculations.

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