Synthesis of 8-aminoquinoline chelating moieties for chemosensor molecules

8-Aminoquinolines are useful molecular motifs for ion sensors. To encourage chemosensor development, new building blocks containing these motifs are essential. 8-Aminoquinoline-2-carbaldehydes are proposed as useful building blocks since their aldehyde group offers the possibility for further transformations. We present a general method for the preparation of these compounds starting from commercially available 8-bromo-2-methylquinoline. Different sidechains for fine-tuning their affinity and selectivity were introduced by a microwave-aided N-arylation using Pd(0) and P-ligands; the desired products were achieved by oxidation. An alternative method is also presented when the product shows high affinity towards the catalyst limiting the effectiveness of the Pd-catalysed the N-arylation. [GRAPHICS]