Mois : juillet 2023

Synthesis
DOI: 10.1055/a-2117-9649

A series of 3-aminoalkylated indoles are efficiently synthesised in a one-pot three-component reaction under microwave irradiation. Magnesium ferrite (MgFe2O4) nanoparticles (10 mol%) have been used as heterogeneous catalyst, which may easily be recovered by application of an external magnet and the recovered catalyst can be reused at least for five runs without affecting the efficiency of the catalyst. The solvent-free protocol developed has advantages of less reaction time, high yields, and easy workup, and the protocol is applicable to various acid base sensitive functional groups present in the substrate. The reported methodology is highly suitable especially for primary amines in addition to secondary amines as one of the components.
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

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Two zinc-porphyrin moieties have been covalently attached through a single, rigid buta-1,3-diyne linkage placed at the ortho position of a meso phenyl ring. Despite of freely rotating around the bis-alkyne axle, such species is adaptable enough to encapsulate a DABCO molecule with a high association constant (K>10⁶ M⁻¹) as supported by in-depth experimental and computational studies.

Abstract

A unique example of a bis-zinc-porphyrin chemical system in which both macrocycles are covalently connected with a single, short buta-1,3-diyne linkage placed at the ortho sites of the meso phenyl rings is presented. This dimeric compound resulted from an homo-coupling side-reaction taking place during a copper-catalyzed click reaction between an alkyne porphyrin and 2-azidopyridine derivatives. Its unexpected formation was rationalized by control experiments and an improved synthesis was achieved under copper-catalyzed Glaser-Hay coupling reaction conditions. This highly sterically congested bis-zinc-porphyrin derivative behaved as a supramolecular host for encapsulating ditopic molecular guests such as 1,4-diazabicyclo[2.2.2]octane (DABCO) with association constant K_1.1 in the order of 10⁶ M⁻¹. This value is comparable to current systems that typically feature several connecting linkages between the two zinc-porphyrin sites resulting in (supra)molecular cages ensuring a high pre-organization. As such, the requirements to take benefit from supramolecular encapsulation can be reduced to a highly rigid, minimal covalent linkage of four atoms between zinc-porphyrins as herein described.

Diketopyrrolopyrrole (DPP) derivatives with thiophene capping rings are widely used as semiconductors in organic electronics. Their optoelectronic properties can be adjusted by adding different electroactive groups or by extending the conjugation of the central core, as well as by regulating their self-assembly through noncovalent interactions. This work describes an efficient method for synthesizing such derivatives.

Abstract

Diketopyrrolopyrrole (DPP) derivatives with thiophene capping rings are widely used as semiconductors in organic electronics. Their optoelectronic properties can be adjusted by adding different electroactive groups or by extending the conjugation of the central core, as well as by regulating their self-assembly through noncovalent interactions. One effective strategy demonstrated to improve the performance and morphology of organic solar cells is incorporating hydrogen-bonding units into DPPs. While the functionalization of the DPP lactams and the coupling of aromatic units to the thiophene rings are the most common procedures to tune the properties of such derivatives, modifying the thiophene capping units with hydrogen-bonding groups is a challenging synthetic task. Despite this difficulty, incorporating amide-containing substituents into the thiophene rings of single core thiophene-capped DPP derivatives could yield exciting results, as the advantages of having hydrogen-bonded π-conjugated systems based on these modified DPPs have not been explored thoroughly. This work reports on an efficient method for synthesizing such derivatives.

Efficient de novo access to 2,3,6-trisubstituted pyridines was successfully synthesized through a mono- or dialkylation reaction between 4/3-alkyl-N-sulfonyl ketimines with 3-chloropropiophenones using DIPEA/NaHCO₃ as a cheap cooperative basic system and subsequent aza-cyclization in the presence of NH₄OAc under an air.

Abstract

An efficient sequential one-pot, two-step pseudo-four-component reaction between 3/4-methyl N-sulfonyl ketimines with 3-chloropropiophenones triggered by DIPEA/NaHCO₃ as a cooperative base and subsequent aza-cyclization using NH₄OAc is reported. This transition-metal-oxidant-free technique concocts new C−C/C=C/C=N−C bonds selectively, guaranteeing acceptable yields of 2,3,6-trisubstituted pyridines possessing ortho-hydroxyaryl/benzenesulfonamide and propiophenone moieties at C2 and C3 positions, respectively. Interestingly, while replacing methyl-substituents with straight alkyl chains of N-sulfonyl ketimines, only a monoalkylation reaction happened with in situ-generated vinyl ketones to deliver promising yields of 3-picoline derivatives. Moreover, the synthetic transmutation of prepared pyridine derivative led to several important classes of pyridocoumarin, 5H-chromenopyridine, and di(pyridin-3-yl) methane derivatives.

The Front Cover shows the porous organic salt with “gate-like” bottlenecks that exhibits gas separation properties depending on the size of the bottlenecks. Oxygen molecules (shown in red) are smaller than the gate size and can easily get in and out. In contrast, nitrogen molecules (shown in blue) are larger than the gate size and can hardly get in and out. Modulation of the gate size will be one of the triggers of future gas separation (e.g., air, toxics, fuel gas). The cover picture was created by Kouki Oka. More information can be found in the Research Article by R. Akai, K. Oka, N. Tohnai et al.

Electrochemical reduction of 1H-thioxanthene-1,4,9-triones, which are representatives of a new class of thioxanthone-like heterocycles, is a three-stage process leading to the formation of the corresponding long-lived radical anions, unstable dianions, and long-lived 1-oxy-4-hydroxy-1H-thioxanthene-9-one radical dianions, followed by the formation of 1,4-dihydroxy-1H-thioxantene-9-ones as the final products.

Abstract

A convenient synthetic route was proposed for the synthesis of 3-methyl-1H-thioxanthene-1,4,9-trione. This compound and its 3-H congener are representatives of a new class of thioxanthone-like heterocycles, which can be used as building blocks for materials used in organic electronics. Electrochemical reduction (ECR) of 1H-thioxanthene-1,4,9-trione and its 3-methyl derivative in DMF and acetonitrile is a three-stage process leading to the formation of the corresponding long-lived radical anions and unstable dianions at the first and second stages, respectively. In a protolytic equilibrium, dianions are converted into 1-oxy-4-hydroxy-1H-thioxanthene-9-one anions. Their one-electron reversible ECR leads to the corresponding radical dianions, followed by the formation of (3-methyl/H)-1,4-dihydroxy-1H-thioxantene-9-ones as the final products. The latter compounds can be converted into the initial (3-methyl/H)-1H-thioxanthene-1,4,9-triones. The main intermediates were characterized using a combination of cyclic voltammetry, EPR spectroscopy, 3D spectroelectrochemistry, and DFT calculations at the (U)B3LYP/6-31+G*/PCM level of theory. A general ECR scheme was proposed for both types of compounds.

A highly diastereoselective base catalyzed addition of nitromethane to the C=N bond of enantiomeric fluorine containing Ellman’s aldimines, R_FCH=NS(O)tert-Bu (R_F=CF₃, CF₂Br, C₂F₅, HC₂F₄), has been successfully developed. The synthetic potential of the resulting β-nitrosulfinylamides was demonstrated through their conversion into optically active α-fluoroalkylated 1,3-nitroamines, 1,3-diamines, and 4-fluoroalkylated imidazolidin-2-ones.

Abstract

A highly diastereoselective addition of nitromethane to the C=N bond of enantiomeric fluorine containing Ellman’s aldimines, R_FCH=NS(O)tert-Bu (R_F=CF₃, CF₂Br, C₂F₅, HC₂F₄), has been successfully developed. The synthetic potential of the resulting β-nitrosulfinylamides was demonstrated through their conversion into optically active α-fluoroalkylated 1,3-nitroamines, 1,3-diamines, and 4-fluoroalkylated imidazolidin-2-ones.

Synthesis
DOI: 10.1055/a-2114-7673

A new one-pot preparation of 3,6-disubstituted pyridazines starting from β-nitro-β,γ-unsaturated ketones and hydrazine monohydrate is presented. The protocol entails two sequential steps, leading to the isolation of the title targets in satisfactory overall yields tolerating a good variety of additional functionalities.
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

Article in Thieme eJournals:
Table of contents  |  Abstract  |  Full text