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Wiley, European Journal of Inorganic Chemistry, 28(2011), p. 4360-4368, 2011

DOI: 10.1002/ejic.201100489

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Selective Copper-Mediated Halogenation of Aromatic Rings Under Mild Conditions

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

A mild copper-mediated halogenation reaction of phenolic rings is reported. The reaction of bis(2-hydroxybenzyl)-1,3-diaminopropane (H2bhbd) with copper(II) chloride in acetonitrile generates linear trinuclear [Cu3(bhcbd)2Cl2](CH3CN), containing modified ligands, whose phenol moieties are selectively chlorinated at the 5-position. Under comparable experimental conditions with copper(II) bromide, bromination of the ligand is observed, albeit at a slower reaction rate. In the presence of trialkylorthoformates, which are used as dehydrating agents, a ring closure of the ligand is observed after removal of copper to yield a product with a six-membered ring. This product has been isolated and characterized by NMR spectroscopy and MS. Similarly, bromination of bis(2-hydroxybenzyl)-1,3-diiminopropane (H2bhbdi) occurs in the presence of copper(II) bromide, with concomitant formation of a linear trinuclear complex. Surprisingly, an asymmetric dinuclear copper(II) coordination compound without chlorination of the ligand is obtained when the related ligand bis(2-hydroxybenzyl)-1,3-diminopropane (H2bhbdi) reacts with copper(II) chloride.