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Access to Functionalized Pyrenes, Peropyrenes, Terropyrenes, and Quarterropyrenes via Reductive Aromatization.

ABSTRACT: Herein we report a versatile concept for the synthesis of fourfold functionalized, soluble pyrenes, peropyrenes, terropyrenes, and quarterropyrenes. They were obtained by a modular stepwise approach towards the rylene scaffold via Suzuki-Miyaura cross coupling, oxidative cyclodehydrogenation in the presence of caesium hydroxide under air, and finally zinc-mediated reductive silylation. The silylated reaction products were characterized by X-ray crystallography. The first example of a synthesized and crystallized quarterropyrene is presented and its oxidation reaction investigated. The functionalized ropyrenes were systematically characterized by means of UV/Vis-NIR and photoluminescence spectroscopy showing a bathochromic shift of 80 nm per naphthalene unit and a nearly linear increase of the extinction coefficients. Cyclic voltammograms and DFT calculations identify them as electron-rich dyes and show a narrowing of the electrochemically determined HOMO-LUMO gap and lower oxidation potentials for the higher homologues.

SUBMITTER: Werner S

PROVIDER: S-EPMC8252597 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Tetrasubstituted Peropyrenes Formed by Reductive Aromatization: Synthesis, Functionalization and Characterization.

Project description:The chromophore class of 1,3,8,10-tetrasubstituted peropyrenes was effectively synthesized from peropyrenequinone via a Zn-mediated reductive aromatization approach. In one step, a symmetric functionalization of the peropyrene backbone introducing silylethers (2,3), pivaloyl (4), triflyl (5) and also phosphinite (6) groups was established. Furthermore, the potential of using 4 and 5 in transition metal catalysed cross couplings was explored leading to 1,3,8,10-tetraaryl (8-11) and tetraalkynyl (7) peropyrenes. The influence of various substituents on the optoelectronic properties of these π-system extended peropyrenes was investigated in solid state by means of X-ray crystallography, in solution by means of UV-Vis and fluorescence spectroscopy and by their redox properties studied via cyclic voltammetry. By comparison with DFT and TD-DFT calculations, it could be elucidated that introduction of a broad variety of substituents in such versatile one or two step procedures leads to peropyrenes with easily tunable HOMO and LUMO energies ranging in a gap window of 0.8 eV. The frontier molecular orbital energies identify the target molecules as promising candidates for hole transporting semiconductors.

| S-EPMC8453513 | biostudies-literature

Access to functionalized steroid side chains via modified Julia olefination.

Project description:Various functionalized steroidal side chains were conveniently accessed by a modified Julia olefination strategy using a common sulfone donor and an appropriate ?-branched aldehyde acceptor. For the coupling of these hindered classes of reaction partners (and in contrast to typically observed trends), the benzothiazolyl(BT)-sulfone anion gave superior outcomes compared to the phenyltetrazolyl(PT)-sulfone anion.

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Facile access to C-glycosyl amino acids and peptides via Ni-catalyzed reductive hydroglycosylation of alkynes.

Project description:C-Glycosyl peptides/proteins are metabolically stable mimics of the native glycopeptides/proteins bearing O/N-glycosidic linkages, and are thus of great therapeutical potential. Herein, we disclose a protocol for the syntheses of vinyl C-glycosyl amino acids and peptides, employing a nickel-catalyzed reductive hydroglycosylation reaction of alkyne derivatives of amino acids and peptides with common glycosyl bromides. It accommodates a wide scope of the coupling partners, including complex oligosaccharide and peptide substrates. The resultant vinyl C-glycosyl amino acids and peptides, which bear common O/N-protecting groups, are amenable to further transformations, including elongation of the peptide and saccharide chains.

| S-EPMC8363649 | biostudies-literature

Facile access to functionalized chiral secondary benzylic boronic esters <i>via</i> catalytic asymmetric hydroboration.

Project description:Allylic and homoallylic phosphonates bearing an aryl or heteroaryl substituent at the γ- or δ-position undergo rhodium-catalyzed asymmetric hydroboration by pinacolborane to give functionalized chiral secondary benzylic boronic esters in yields up to 86% and enantiomer ratios up to 99 : 1. Compared to minimally-functionalized terminal and 1,1-disubstituted vinyl arenes, there are relatively few reports of efficient catalytic asymmetric hydroboration (CAHB) of more highly functionalized internal alkenes. Phosphonate substrates bearing a variety of common heterocyclic ring systems, including furan, indole, pyrrole and thiophene derivatives, as well as those bearing basic nitrogen substituents (e.g., morpholine and pyrazine) are tolerated, although donor substituents positioned in close proximity of the alkene can influence the course of the reaction. Stereoisomeric (E)- and (Z)-substrates afford the same major enantiomer of the borated product. Deuterium-labelling studies reveal that rapid (Z)- to (E)-alkene isomerization accounts for the observed (E/Z)-stereoconvergence during CAHB. The synthetic utility of the chiral boronic ester products is illustrated by stereospecific C-B bond transformations including stereoretentive electrophile promoted 1,2-B-to-C migrations, stereoinvertive SE2 reactions of boron-ate complexes with electrophiles, and stereoretentive palladium- and rhodium-catalyzed cross-coupling protocols.

| S-EPMC6520923 | biostudies-literature

Reductive Amination of Dialdehyde Cellulose: Access to Renewable Thermoplastics.

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| S-EPMC9832504 | biostudies-literature

Deacylative transformations of ketones via aromatization-promoted C-C bond activation.

Project description:Carbon-hydrogen (C-H) and carbon-carbon (C-C) bonds are the main constituents of organic matter. Recent advances in C-H functionalization technology have vastly expanded our toolbox for organic synthesis1. By contrast, C-C activation methods that enable editing of the molecular skeleton remain limited2-7. Several methods have been proposed for catalytic C-C activation, particularly with ketone substrates, that are typically promoted by using either ring-strain release as a thermodynamic driving force4,6 or directing groups5,7 to control the reaction outcome. Although effective, these strategies require substrates that contain highly strained ketones or a preinstalled directing group, or are limited to more specialist substrate classes5. Here we report a general C-C activation mode driven by aromatization of a pre-aromatic intermediate formed in situ. This reaction is suitable for various ketone substrates, is catalysed by an iridium/phosphine combination and is promoted by a hydrazine reagent and 1,3-dienes. Specifically, the acyl group is removed from the ketone and transformed to a pyrazole, and the resulting alkyl fragment undergoes various transformations. These include the deacetylation of methyl ketones, carbenoid-free formal homologation of aliphatic linear ketones and deconstructive pyrazole synthesis from cyclic ketones. Given that ketones are prevalent in feedstock chemicals, natural products and pharmaceuticals, these transformations could offer strategic bond disconnections in the synthesis of complex bioactive molecules.

| S-EPMC6426660 | biostudies-literature

Palladium catalysed C-H arylation of pyrenes: access to a new class of exfoliating agents for water-based graphene dispersions.

Project description:A new and diverse family of pyrene derivatives was synthesised via palladium-catalysed C-H ortho-arylation of pyrene-1-carboxylic acid. The strategy affords easy access to a broad scope of 2-substituted and 1,2-disubstituted pyrenes. The C1-substituent can be easily transformed into carboxylic acid, iodide, alkynyl, aryl or alkyl functionalities. This approach gives access to arylated pyrene ammonium salts, which outperformed their non-arylated parent compound during aqueous Liquid Phase Exfoliation (LPE) of graphite and compare favourably to state-of-the-art sodium pyrene-1-sulfonate PS1. This allowed the production of concentrated and stable suspensions of graphene flakes in water.

| S-EPMC8157272 | biostudies-literature

Homogeneous cobalt-catalyzed reductive amination for synthesis of functionalized primary amines.

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| S-EPMC6884468 | biostudies-literature

Alternative Access to Functionalized 2,8-Ethanonoradamantane Derivatives.

Project description:7a-(Methoxycarbonyl)-N-methyl-1,3a,5,6,7,7a-hexahydro-4H-1,4,6-(epiethane[1,1,2]triyl)indene-4,9-dicarboximide has been prepared through a modification of a previous synthetic sequence, in which the benzyloxymethyl hydroxyl protecting group has been replaced by methoxymethyl, to avoid the apparent formation of a benzyl ester derivative as a side product. The overall yield of the new synthetic sequence is comparable to the previous one. Two advantages of the new procedure are: (a) no benzyl ester was formed and (b) a stereoisomeric mixture of syn- and anti-alcohols at the beginning of the synthetic sequence could be separated and the rest of the synthesis could be carried out with the main syn-stereoisomer instead of the corresponding stereoisomeric mixture as it was the case in the previous process. Additionally, several functional 2,8-ethanonoradamantane derivatives have been prepared.

| S-EPMC6152640 | biostudies-literature

Nickel-catalyzed three-component olefin reductive dicarbofunctionalization to access alkylborates.

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| S-EPMC8163243 | biostudies-literature

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