emile escoudé

Synthesis
DOI: 10.1055/a-1549-1082

We report an efficient method for the direct β-acylation of 2-ylideneoxindoles with acyl chlorides that is catalyzed by organophosphanes in the presence of base. A variety of functionalized 2-ylideneoxindoles were prepared in moderate to good yields under mild, metal-free conditions via a tandem phospha-Michael/O-acylation/intramolecular cyclization/rearrangement sequence. Mechanistic investigations revealed that C–O bond cleavage on a possible betaine intermediate is the key step for the installation of the keto-functionality at the β-position of 2-ylideneoxindoles in a highly stereospecific manner. The synthetic utility of this protocol could also be proven by a scale-up reaction and synthetic transformations of the products.
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

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Synthesis
DOI: 10.1055/a-1509-5954

Nickel-catalyzed reductive homocoupling 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 show that the dianionic anthracene-9,10-diyl ligand reduces the two aryl ether substrates, resulting in the homocoupling reaction through supply of 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.
[...]

Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

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