ChemInform Abstract: Powerful Fluoroalkoxy Molybdenum(V) Reagent for Selective Oxidative Arene Coupling Reaction.

A novel dinuclear fluoroalkoxy Mo(V)-complex is efficient as reagent for the oxidative arene coupling of electron-rich arenes with superior reactivity compared to MoCl5 and MoCl5/TiCl4.

Leistungsstarkes Fluoralkoxy-Molybdän(V)-Reagens für die selektive oxidative Arenkupplung

Wir stellen ein neues Fluoralkoxy-Molybdan(V)-Reagens 1, mit im Vergleich zu MoCl5 oder MoCl5/TiCl4 hoherer Reaktivitat und Selektivitat in der oxidativen Kupplung von Arenen vor. Haufige Nebenreaktionen wie Chlorierung und/oder Oligomerenbildung werden erheblich reduziert, sodass ein leistungsstarkes und nutzliches Reagens fur die oxidative Kupplung erhalten wird. Theoretische Untersuchungen der Wechselwirkung des Reagens mit 1,2-Dimethoxybenzol-artigen Substraten deuten auf einen Innenspharen-Elektronentransfer gefolgt von einem radikalkationischen Reaktionspfad fur den oxidativen Kupplungsprozess hin. ESR-spektroskopische und elektrochemische Untersuchungen, Rontgenkristallstrukturanalys…

Modular Approach to 9-Monosubstituted Fluorene Derivatives Using Mo(V) Reagents.

Oxidative coupling using molybdenum(V) reagents provides fast access to highly functionalized 9-monosubstituted fluorenes. This synthetic approach is highly modular, is high yielding, and tolerates a variety of labile moieties, e.g. amides or iodo groups. The established protocol leads to promising precursors for pharmacologically important analogues of melatonin.

Oxidative (Cross-)Coupling Reactions Mediated by C-H Activation of Thiophene Derivatives by Using Molybdenum(V) Reagents

Oxidative coupling by using molybdenum pentachloride provides fast and modular access to sophisticated thienoacenes in excellent yields. The coupling process can be accomplished with thiophene and benzothiophene derivatives and provides various complex skeletons such as spirocyclic compounds. In this approach, the first cross-coupling reactions with the use of MoCl5 were established and important motifs for semiconducting materials were synthesized.

Überoxidation als Schlüsselschritt im Mechanismus der MoCl5 - vermittelten dehydrierenden Arenkupplung

MoVReagents in Organic Synthesis

The use of MoV reagents, and in particular MoCl5, in organic synthesis is surveyed. The oxidative treatment of aromatic substrates is the most common application. The unique properties of these reagents are due to their high oxidative power combined with exquisite Lewis acid properties. In several examples MoV reagents outperform other common oxidative coupling reagents. C–C bond formation through inter- and intramolecular oxidative coupling can lead to selective formation of five- to eight-membered ring systems. Mechanistic investigations of the courses of reactions involving MoV reagents and aromatic substrates indicate that radical cations are initially formed, entering the oxidative cou…

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

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…

ChemInform Abstract: Oxidative (Cross-)Coupling Reactions Mediated by C-H Activation of Thiophene Derivatives by Using Molybdenum(V) Reagents.

The use of MoCl5 renders possible the preparation of various synthetically important polycyclic thienoacenes.

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

ChemInform Abstract: Modular Approach to 9-Monosubstituted Fluorene Derivatives Using MoVReagents.

Oxidative cyclization reaction of 2-aryl-substituted cinnamates to form phenanthrene carboxylates by using MoCl5.

The oxidative cyclization reaction of 2-aryl cinnamates and derivatives thereof can be easily performed with MoCl5 as the oxidant. This powerful reagent allows oxidative coupling reactions for which other reagents fail. The best results are obtained when the 2-phenyl substituent of the cinnamate is equipped with two methoxy groups. Even iodo moieties in the bay region of phenanthrene are tolerated under the reaction conditions. If naphthalene moieties are involved, a rearrangement of the skeleton occurs, providing an elegant route to highly functionalized angular arenes. The cyclization is demonstrated for 15 example substrates with isolated yields of up to 99 % for the phenanthrene derivat…

ChemInform Abstract: Oxidative Cyclization Reaction of 2-Aryl-Substituted Cinnamates to Form Phenanthrene Carboxylates by Using MoCl5.

The reagent mixture MoCl5/TiCl4 is successfully applied for the oxidative cyclization of α-aryl substituted cinnamates to the corresponding phenanthrenes.

Molybdenum Pentachloride Mediated Synthesis of Spirocyclic Compounds by Intramolecular Oxidative Coupling

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.

Cover Picture: Oxidative Cyclization Reaction of 2-Aryl-Substituted Cinnamates To Form Phenanthrene Carboxylates by Using MoCl5 (Chem. Eur. J. 39/2014)

Crystal structure of ethyl 2-(di-eth-oxy-phosphor-yl)-2-(2,3,4-tri-meth-oxy-phen-yl)acetate.

The title compound, C17H27O8P, was prepared by Michaelis–Arbuzov reaction of ethyl 2-bromo-2-(2,3,4-trimethoxyphenyl)acetate and triethyl phosphite. Such compounds rarely crystallize, but single crystals were recovered after the initial oil was left for approximately 10 years. The bond angle of thesp3-hybridized C atom connecting the benzene derivative with the phospho unit is widened marginally [112.5 (2)°]. The terminal P—O bond length of 1.464 (2) Å clearly indicates a double bond, whereas the two O atoms of the ethoxy groups connected to the phosphorous atom have bond lengths of 1.580 (2) Å and 1.581 (3) Å. The three methoxy groups emerge out of the benzene-ring plane due to steric hind…

ChemInform Abstract: Molybdenum Pentachloride Mediated Synthesis of Spirocyclic Compounds by Intramolecular Oxidative Coupling.

Oxidative treatment of 4-methoxy substituted 2-aryl cinnamates leads to an dealkylative C—C coupling and gives access to spirocyclic compounds.

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

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…

Initial Radical Cation Pathway in the Mo2Cl10-Mediated Dehydrogenative Arene Coupling

Experimental (EPR) and theoretical (DFT) evidence is provided for radical cation formation as initial step in the Mo2Cl10-mediated dehydrogenative arene coupling. The initial electron transfer from methoxyarenes to molybdenum proceeds via an inner sphere mechanism.

CCDC 1415863: Experimental Crystal Structure Determination

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CCDC 966311: Experimental Crystal Structure Determination

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CCDC 804368: Experimental Crystal Structure Determination

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CCDC 1415860: Experimental Crystal Structure Determination

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CCDC 1415861: Experimental Crystal Structure Determination

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CCDC 1427184: Experimental Crystal Structure Determination

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CCDC 1415862: Experimental Crystal Structure Determination

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CCDC 1427185: Experimental Crystal Structure Determination

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CCDC 1419863: Experimental Crystal Structure Determination

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CCDC 966309: Experimental Crystal Structure Determination

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CCDC 804367: Experimental Crystal Structure Determination

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CCDC 966310: Experimental Crystal Structure Determination

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