Nickel-catalyzed Homo-coupling of Aryl Ethers with Magnesium Anthracene Reductant

Synthesis ◽

10.1055/a-1509-5954 ◽

2021 ◽

Author(s):

Vishal Kumar Rawat ◽

Kosuke Higashida ◽

Masaya Sawamura

Keyword(s):

Dft Calculations ◽

Bond Cleavage ◽

Low Cost ◽

Coupling Reaction ◽

Reducing Agent ◽

Aryl Ether ◽

Bimetallic System ◽

Cleavage Reactions ◽

Aryl Ethers

Nickel-catalyzed reductive homo-coupling of aryl ethers has been achieved with Mg(anthracene)(thf)3 as a readily available low-cost reductant. DFT calculations provided a rationale for the specific efficiency of the diorganomagnesium-type two-electron reducing agent. The calculations showed that the dianionic anthracene-9,10-diyl ligand reduces the two aryl ether substrates resulting in the homo-coupling reaction through supplying the electrons to the Ni-Mg bimetallic system to form organomagnesium nickel(0)-ate complexes, which cause two sequential C–O bond cleavage reactions. The calculations also showed cooperative actions of Lewis-acidic magnesium atoms and electron-rich nickel atoms in the C–O cleavage reactions.

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The structure, photochemical reactivity, and photophysical properties of adamantyl X-substituted aryl ethers and a comparison with the alkyl groups, methyl, tert-butyl, and allyl

Canadian Journal of Chemistry ◽

10.1139/v05-117 ◽

2005 ◽

Vol 83 (9) ◽

pp. 1237-1252 ◽

Cited By ~ 2

Author(s):

A L Pincock ◽

J A Pincock

Keyword(s):

Excited State ◽

Rate Constants ◽

Singlet State ◽

Bond Cleavage ◽

Photophysical Properties ◽

Excited Singlet State ◽

Quantum Yields ◽

Aryl Ether ◽

Excited Singlet ◽

Aryl Ethers

The structure, photophysical properties, and photochemistry of the adamantyl aryl ethers 1 in both methanol and cyclohexane have been examined. UV absorption spectra, 13C NMR chemical shifts, X-ray structures, and Gaussian calculations (B3LYP/6-31G(d)) indicate that these ethers adopt a 90° conformer in the ground state. In contrast, fluorescence spectra, excited singlet state lifetimes, and calculations (TDDFT) indicated a 0° conformer is preferred in the first excited singlet state S1. Irradiation in either solvent results in the formation of adamantane and the corresponding phenol as the major products, both derived from radical intermediates generated by homolytic cleavage of the ether bond. The 4-cyano substituted ether 1j was the only one to form the ion-derived product, 1-methoxyadamantane (16% yield), on irradiation in methanol. Rate constants of bond cleavage for these ethers from S1 were estimated by two different methods by comparison with the unreactive anisoles 2, but the effect of substituents was too small to determine structurereactivity correlations. The temperature dependence of the quantum yields of the fluorescence of the unsub stituted, 4-methoxy and 4-cyano derivatives of 1 and 2 were also determined. These results indicated that the activated process for 1 was mainly bond cleavage for the 4-cyano substrate whereas for 2, it was internal conversion and intersystem crossing. Key words: aryl ether photochemistry, fluorescence, excited-state rate constants, excited-state temperature effects.

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Hydrogenation-dehydrogenation and cleavage functions of hydrorefining catalysts studied by the reaction of tetrahydrothiophene

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19862770 ◽

1986 ◽

Vol 51 (12) ◽

pp. 2770-2780 ◽

Cited By ~ 1

Author(s):

Alexandra Drahorádová ◽

Miroslav Zdražil

Keyword(s):

Activated Carbon ◽

Catalyst Surface ◽

Bond Cleavage ◽

Unsaturated Hydrocarbons ◽

Cleavage Reactions

The reaction of tetrahydrothiophene in a stream of nitrogen was used to study the relations between dehydrogenation and C-S cleavage reactions on sulphided Co-Mo/Al2O3 catalysts. The course of the reaction was compared for Co-Mo catalysts supported on alumina and activated carbon, for alumina alone as well as for a Pt/C catalyst. The effect of substitution of nitrogen for hydrogen, of the addition of water to the feed, of pre-sulphidation of catalysts and their deactivation by coking on the rate and selectivity of the reaction were also investigated. The results showed that hydrogenation-dehydrogenation and dehydrosulphurization activity of the sulphide catalysts have the same origin. Hydrogen accelerates dehydrosulphurization on the sulphide catalysts by removing sulphur and unsaturated hydrocarbons formed on catalyst surface by C-S bond cleavage reactions.

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