- Radical-Cation Catalysis in the Synthesis of Diphenylmethanes via the Dealkylative Coupling of Benzylic Ethers
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The dealkylative coupling of benzyl alkyl ethers (ArCH2OR) to yield the corresponding diarylmethanes (ArCH2Ar) together with dialkoxymethane (ROCH2OR) is catalyzed by small amounts of 1-electron oxidants (such as aromatic cation radicals, NO(1+), etc.) or by an equivalent electrochemical (anodic) method.The catalytic method is successfully employed for the facile synthesis of a novel macrocyclic crown ether 18 that contains a diarylmethane linkage.On the basis of the spectral observation of the radical cation ArCH2OR.+ and the excellent catalytic efficiency with turnover numbers in excess of 1E2, an electron-transfer and an alternative electrophilic chain mechanism are discussed for the dealkylative coupling process.
- Rathore, Rajendra,Kochi, Jay K.
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p. 7479 - 7490
(2007/10/03)
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- A New Synthesis of Anthraquinones Using Dihydro-oxazoles and Grignard Reagents Derived from Mg(Anthracene)(THF)3
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A general synthesis of anthraquinones which depends on the displacement of the methoxy group from an o-methoxyaryldihydro-oxazole by a methoxy substituted benzylmagnesium chloride, generated by using a magnesium-anthracene complex, has been developed.The masked benzylbenzoic acids which result from these reactions are deprotected and then ring-closed to anthrones which on oxidation yield anthraquinones.In this way, the followeing naturally occurring anthraquinones (or derivatives thereof have been synthesized): chrysophanol (9), islandicin (19), digitopurpone (21), tri-O-methylemodin (26), and di-O-methylsoranjidiol (29).
- Nicoletti, Teresa M.,Raston, Colin L.,Sargent, Melvyn V.
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p. 133 - 138
(2007/10/02)
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