Search results for "catalyzed"

Copper-Catalyzed Aerobic Oxidative Alkynylation of 3,4-Dihydroquinoxalin-2-ones

2019

Herein, we described a ligand-free copper-catalyzed aerobic oxidative functionalization of 3,4-dihydroquinoxalin-2(1H)-ones with terminal alkynes using visible-light and oxygen as terminal oxidant to give 3-ethynyl-3,4-dihydroquinoxalin-2(1H)-one, cyclic propargylic amines, in moderate to good yields. Moreover, we demonstrate the versatility of the 3-ethynyl-3,4-dihydroquinoxalin-2(1H)-ones obtained by preparing several 3,4-dihydroquinoxalin-2-one derivatives.

Comparison Study of Two Differently Clicked 18F-Folates—Lipophilicity Plays a Key Role

2018

Within the last decade, several folate-based radiopharmaceuticals for Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET) have been evaluated; however, there is still a lack of suitable 18F-folates for clinical PET imaging. Herein, we report the synthesis and evaluation of two novel 18F-folates employing strain-promoted and copper-catalyzed click chemistry. Furthermore, the influence of both click-methods on lipophilicity and pharmacokinetics of the 18F-folates was investigated. 18F-Ala-folate and 18F-DBCO-folate were both stable in human serum albumin. In vitro studies proved their high affinity to the folate receptor (FR). The lipophilic character of …

Intermolecular oxidative dehydrogenative 3,3′-coupling of benzo[b]furans and benzo[b]thiophenes promoted by DDQ/H+: total synthesis of shandougenine B

2016

With an excess of a strong acid, 2,3-dichloro-5,6-dicyano-1,4-quinone (DDQ) is shown to promote metal-free intermolecular oxidative dehydrogenative (ODH) 3,3'-coupling of 2-aryl-benzo[b]furans and 2-aryl-benzo[b]thiophenes up to 92% yield as demonstrated with 9 substrates. Based on the analysis of oxidation potentials and molecular orbitals combined with EPR, NMR and UV-Vis observations, the studied reaction is initiated by a DDQ-substrate charge transfer complex and presumably proceeds via oxidation of the substrate into an electrophilic radical cation that further reacts with another molecule of a neutral substrate. The coupling reactivity can easily be predicted from the oxidation potent…

Trienediolates of hexadienoic acids in synthesis. Addition to unsaturated ketones. A convergent approach to the synthesis of retinoic acids

1995

Abstract The regioselectivity of the addition of the lithium trienediolates generated from hexa-2,4dienoic acids 1 and 2 or the dihydropyran-2ones 4 and 5 to unsaturated ketones 6 is studied. Equilibration conditions favour reaction of the trienediolates through their ω carbon, and the ketones according to 1,2- and 1,4-additions. β-Ionone 6a and the aryl-butenone 6b lead to the 1,2-ω-adducts 8 , which undergo a facile acid catalyzed dehydration to retmoic acids 11 . On reaction with the unsaturated ketone 6b or with the aryl ketones 21 , the trimethyldihydropyran-2one S leads to γ-adducts derived from deprotonation of the chain methyl mbstituent along with the 1,4-ω-adducts.

ChemInform Abstract: Trienediolates of Hexadienoic Acids in Synthesis. Addition to Unsaturated Ketones. A Convergent Approach to the Synthesis of Ret…

2010

Abstract The regioselectivity of the addition of the lithium trienediolates generated from hexa-2,4dienoic acids 1 and 2 or the dihydropyran-2ones 4 and 5 to unsaturated ketones 6 is studied. Equilibration conditions favour reaction of the trienediolates through their ω carbon, and the ketones according to 1,2- and 1,4-additions. β-Ionone 6a and the aryl-butenone 6b lead to the 1,2-ω-adducts 8 , which undergo a facile acid catalyzed dehydration to retmoic acids 11 . On reaction with the unsaturated ketone 6b or with the aryl ketones 21 , the trimethyldihydropyran-2one S leads to γ-adducts derived from deprotonation of the chain methyl mbstituent along with the 1,4-ω-adducts.

Bimodal tracers synthesis for medical imaging PET/MRI

2015

Today physicians can use a wide variety of medical imaging techniques to establish early and accurate diagnosis. Nevertheless, each modality has its own advantages and drawbacks. This is why bi- or multimodality approach seems interesting. Among them, PET/MRI combination seems very promising because it can bring complementary informations. It is therefore necessary to inject to patients tracers specific to each imaging modality. This work described the synthesis of molecular platforms for MRI and PET imaging, according to 2 different strategies. The first one consisted in the synthesis of a DO3A macrocycle allowing the chelation of both gadolinium for MRI and gallium 68 for PET. The aim her…

Influence of conformational factors on acid-catalyzed cyclizations of germacranolides: Molecular structure of the cyclization products of gallicin an…

1995

Acid-catalyzed cyclization of the natural germacranolide gallicin (8) yielded, among other products, the 1,4-epoxyeudes-manolide 9, which has a trans-fused decaline system. Under the same conditions the closely related germacranolide shonachalin A (8α-hydroxygallicin) (3) cyclized to the eudesmanolide 4 with a cis fused decaline system. The structures of these cyclization products were secured by means of chemical correlations and X-ray diffraction analyses.

Front Cover: Iron-Catalyzed C−O Bond Activation: Opportunity for Sustainable Catalysis (ChemSusChem 20/2017)

2017

Iron-Catalyzed C−O Bond Activation: Opportunity for Sustainable Catalysis

2017

Oxygen-based electrophiles have emerged as some of the most valuable cross-coupling partners in organic synthesis due to several major strategic and environmental benefits, such as abundance and potential to avoid toxic halide waste. In this context, iron-catalyzed C-O activation/cross-coupling holds particular promise to achieve sustainable catalytic protocols due to its natural abundance, inherent low toxicity, and excellent economic and ecological profile. Recently, tremendous progress has been achieved in the development of new methods for functional-group-tolerant iron-catalyzed cross-coupling reactions by selective C-O cleavage. These methods establish highly attractive alternatives t…

Expanding the Variety of Zirconium‐based Inorganic Building Units for Metal–Organic Frameworks

2019

Two new zirconium-based metal-organic frameworks with the composition [Zr6 O4 (OH)4 (OAc)6 (BDC)3 ] (CAU-26) and [Zr5 O4 (OH)4 (OAc)4 (BDC)2 ] (CAU-27) are reported, which were synthesized from acetic acid, a rarely utilized but green and sustainable solvent (BDC2- : 1,4-benzenedicarboxylate). Structure determination aided by automated electron diffraction tomography revealed that CAU-26 is composed of layers of well-known {Zr6 O8 } clusters interconnected by terephthalate ions. In contrast CAU-27 exhibits a three-dimensional structure with a so far unknown type of one-dimensional inorganic building unit (IBU), which can be rationalized as condensed polyhedron-sharing chains of {Zr6 O8 } cl…