Search results for "oxidative coupling"

Mild, Fast, and Easy To Conduct MoCl5-Mediated Dehydrogenative Coupling Reactions in Flow

2018

A convenient and straightforward approach to performing oxidative coupling reactions in flow is presented. A collection of electron-rich benzene derivatives was subjected to this protocol, and the distinct utility of molybdenum pentachloride (MoCl5) is established. Using this unexplored protocol, biphenyls could be obtained in 21–91% isolated yield. This simple protocol opens a new chapter in reagent-mediated dehydrogenative coupling reactions, and yields are compared to classical approaches.

Molybdenum Pentachloride Mediated Synthesis of Spirocyclic Compounds by Intramolecular Oxidative Coupling

2015

The oxidative treatment of (m)ethyl 2-aryl cinnamates equipped with methoxy groups in position 4 of the phenyl moiety promote the formation of cyclohexadienone substructures. This dealkylative oxidative C–C coupling gives access to spirocyclic compounds and avoids the construction of the corresponding phenanthrenes. Furthermore, the transformation can be expanded to other spirocyclic systems.

Over-Oxidation as the Key Step in the Mechanism of the MoCl5-Mediated Dehydrogenative Coupling of Arenes.

2015

Molybdenum pentachloride is an unusually powerful reagent for the dehydrogenative coupling of arenes. Owing to the high reaction rate using MoCl5, several labile moieties are tolerated in this transformation. The mechanistic course of the reaction was controversially discussed although indications for a single electron transfer as the initial step were found recently. Herein, based on a combined study including synthetic investigations, electrochemical measurements, EPR spectroscopy, DFT calculations, and mass spectrometry, we deduct a highly consistent mechanistic scenario: MoCl5 acts as a one-electron oxidant in the absence of TiCl4 and as two-electron oxidant in the presence of TiCl4, bu…

Unusual redox play of Mo(V/IV) during oxidative aryl–aryl coupling

2012

The oxidative treatment of a suitable 1,3-diarylpropene precursor by MoCl5 causes a series of redox steps yielding a dimer of dibenzo[a,c]cycloheptene. After the oxidative aryl–aryl bond formation, a C,H activation occurs providing a tropylium intermediate. Upon aqueous workup the metal waste acts as reductive media generating the dimer in an almost quantitative manner. The oxidative generation of the tropylium species as well as the subsequent redox play by the metal waste is unique and unprecedented. The dimeric compound can be oxidatively cleaved and subsequently decarboxylated providing the key intermediate of a previous synthesis of metasequirin-B derivatives.

Oxidative transformation of aryls using molybdenum pentachloride.

2012

Molybdenum pentachloride combines a strong Lewis acid character with an unusually high oxidation potential creating a powerful reagent for oxidative transformations. Since the oxidative coupling reaction of aryls is induced at an extraordinarily high reaction rate, a variety of labile groups, e.g. iodo, tert-alkyl, etc., are tolerated on the aromatic core. Furthermore, the co-formed molybdenum salts can either be exploited for template effects to obtain uncommon geometries in a preferred manner, or redox-play starts after aqueous workup. Therefore MoCl(5) represents a unique and easily available reagent.

ChemInform Abstract: An Easy Access to Fused Chromanones via Rhodium Catalyzed Oxidative Coupling of Salicylaldehydes with Heterobicyclic Olefins.

2016

Diazabicyclic and urea-derived bicyclic olefins react with salicylaldehydes to produce various types of fused chromanone systems of biological interest in a single step (mechanism).

MoVReagents in Organic Synthesis (Eur. J. Org. Chem. 11/2016)

2016

Structural Characterization of Isomeric Dimers from the Oxidative Oligomerization of Catechol with a Biomimetic Catalyst

2007

In a previous paper, it has been reported about the formation of catechol di-, tri- and tetramers within an oxidative polymerization catalyzed by synthetic water-soluble iron-porphyrin as an efficient alternative to bio-labile natural peroxidase. It has also been demonstrated the occurrence of both C-C and C-O-C coupling mechanisms. However, since the coupling products were determined by mass spectroscopy, the exact bonding position could not have been precisely ascertained for the C-C bonded isomeric dimers that are the dominant products of catechol oligomerization. Therefore, here isolation and characterization of catechol isomeric dimers, obtained by oxidative coupling under the catalysi…

Powerful Fluoroalkoxy Molybdenum(V) Reagent for Selective Oxidative Arene Coupling Reaction

2013

We introduce the novel fluoroalkoxy molybdenum(V) reagent 1 which has superior reactivity and selectivity in comparison to MoCl5 or the MoCl5 /TiCl4 reagent mixture in the oxidative coupling reactions of aryls. Common side reactions, such as chlorination and/or oligomer formation, are drastically diminished creating a powerful and useful reagent for oxidative coupling. Theoretical treatment of the reagent interaction with 1,2-dimethoxybenzene-type substrates indicates an inner-sphere electron transfer followed by a radical cationic reaction pathway for the oxidative-coupling process. EPR spectroscopic and electrochemical studies, X-ray analyses, computational investigations, and the experim…

ChemInform Abstract: Synthesis of Highly Functionalized 9,10-Phenanthrenequinones by Oxidative Coupling Using MoCl5.

2012

An efficient method to prepare functionalized 9,10-phenanthrenequinones including the natural cypripediquinone A (VIIIa) is reported.