Synthesis and functionalisation of 5-substituted neocuproine derivatives

2,9-Dimethyl-1,10-phenanthroline (neocuproine, 1) was functionalised selectively in the 5-position. Silylation of the methyl groups followed by bromination in the 5-position was carried out to give the bis(tert-butyldimethylsilyl)-substituted neocuproine 3 and 5-bromo-2,9-dimethyl-1,10-phenanthroline (4) after deprotection. Compounds 3 and 4 are versatile building blocks for the construction of 5-substituted neocuproines. Palladium-catalysed couplings (Suzuki, Sonoga-shira, Buchwald/Hartwig) can be utilized to connect different substituents to the 1,10-phenanthroline moiety (5-7). These substituents may carry additional functional groups that allow the further connection of the 5-substituted neocuproines to form other molecules. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).