Preparation of symmetric dibromides of 1,10-phenanthroline

Bromation of 1,10-phenanthroline with Br 2 proceeds smoothly in the presence of S 2 Cl 2 and pyridine to give 3,8-dibromo-1,10-phenanthroline in good yield. Bromation of 2,9-dibutoxy-1,10-phenanthroline with Br 2 , in an aqueous medium gives 5,6-dibromo-2,9-dibutoxy-1,10-phenanthroline selectively. Similar bromination of 4,7-dibutoxy-1,10-phenanthroline with Br 2 gives 3,8-dibromo-4,7-dibutoxy-1,10-phenanthroline, which forms a 1:1 adduct with Cu(NO 3 ) 2 . Molecular structure of the 1:1 adduct has been determined by X-ray crystallography. Keywords: bromination, 1,10-phenanthroline, 3,8-dibromo-1,10-phenanthroline.