Electrooxidation of certain naphthalene derivatives

Monatshefte fuer Chemie/Chemical Monthly (Impact Factor: 1.22). 05/2008; 139(5):513-519. DOI: 10.1007/s00706-007-0818-8


Naphthalene and alkylnaphthalenes are electro-oxidized to give many products, of which 1,4-naphthoquinones and binaphthyls
are the most stable, especially in the case of substrates, which are not substituted in α-positions. On the other hand, α-substituted
naphthalenes give the respective naphthoquinols as the main products. Interestingly, 1,2-naphthoquinones are not separated
as products, instead, a fragmentation of one of the rings leads to oxidation products, in which the 1,2-bond in naphthalene
is broken to form dialdehydes or diketones. An anodic formation of binaphthyls is described, starting from alkyl-substituted
naphthalenes, dissolved in acetone-water (1:1 v/v) and using 0.1 M (CH3)4N(BF4) supporting electrolyte. Several isomeric binaphthyls were obtained depending on the substrates. The structure of the binaphthyls
formed is discussed based on molecular orbital calculations using the AM1 program. Cyclic voltammetric oxidation curves are
shown for naphthalene and three methyl derivatives.

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    ABSTRACT: This article reports on the applications of electrochemistry for the generation of radicals as neutral, cationic, and anionic intermediates and their use in preparative reactions for the formation of carbon–carbon and carbon–heteroatom bonds. The focus of this article is on electrochemical oxidation reactions of enol ethers, ketene acetals, and electron-rich aromatic compounds. Furthermore, recent advances in the electrochemically induced synthesis of four-membered ring systems and biaryl compounds are covered. The oxidative carbon–carbon bond formation by Kolbe electrolysis concludes the section dealing with oxidative transformations. The section describing reductive processes consists of indirect electrochemical reduction of alkylhalides and thioesters, as well as the reductive interconversion of functional groups described recently.Keywords:electrochemistry;radical intermediates;enol ethers;ketene acetals;furanes;Kolbe electrolysis;biphenylenes;indirect electrolysis;nickel redox catalysis;aminoxy radicals;oxidation;reduction
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