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Copper Mediated Oxidative Coupling 2001

Article                                                                                         

Copper(II)-Mediated Oxidative Coupling of 2-Aminonaphthalene Homologues. Competition between the Straight Dimerization and the Formation of Carbazoles

Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, U.K., Department of Organic Chemistry, Charles University, Hlavova 2030, 128 40 Prague 2, Czech Republic, Department of Chemistry, University of Leicester, Leicester, LE1 7RH, U.K., Neuroscience Research Centre, Merck Sharp & Dohme, Terlings Park, Harlow CM20 2QR, U.K., and Department of Inorganic Environmental Chemistry, Chalmers University of Technology, 41296 Göteborg, Sweden
J. Org. Chem., 2001, 66 (4), pp 1359–1365
DOI: 10.1021/jo005691w
Publication Date (Web): January 31, 2001
Copyright © 2001 American Chemical Society

Abstract

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Whereas the Cu(II)-mediated oxidative coupling of 2-aminonaphthalenes 7a and 7b results in the clean formation of 1,1‘-binaphthyls 13a and 13b, respectively, their higher homologues and congeners 812 have been found to exhibit a different reaction pattern. Thus, 2-aminoanthracene (8) gave a ∼1:1 mixture of the expected bianthryl derivative 15 and the carbazole 16, whereas the 9-aminophenanthrene (10), 3-phenyl-1-aminonaphthalene (11), and 2-aminochrysene (12) produced almost exclusively the corresponding carbazoles 19, 20, and 21, respectively. By contrast, the isomeric 3-aminophenanthrene (9) gave rise to the azo compound 17 as a result of the preferential oxidation on the nitrogen. The carbazoles have been shown to arise directly from the coupling reactions rather than from the primarily formed binaphthyls. Alternatively, carbazole 19 can also be prepared from 1b on reaction with hydrazine. On the other hand, treatment of 3a with hydrazine resulted in the formation of a ∼2:7 mixture of amine 11 and arylhydrazine 22. 2,2‘-Diamino-1,1‘-bianthryl (15) has been resolved into enantiomers via cocrystallization with (−)-N-benzylcinchonidinium chloride and shown to have (R)-(−)-15 configuration by X-ray crystallography.





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