Preparation of carboxylate derivatives of terpyridine via the furan pathway.

This protocol describes a practical procedure for the preparation of terpyridine carboxy derivatives, which have numerous applications, including being photoactive components of functional materials, and which can be used in medicinal chemistry or in catalysis. This protocol relies on the permanganate-mediated oxidation of a furan ring on the polypyridine system. The procedure involves three stages. First, a furan-functionalized terpyridine is synthesized from furfuraldehyde and a 2-acetylpyridine derivative. Second, the furan ring is oxidized thus providing a carboxylic acid. Finally, esters are prepared by reaction of the acids in refluxing alcohols. The procedure is simple, uses a reagent available from renewable resources (furfural) and avoids the use of noxious reagents or solvents, thus making it more environmentally friendly when compared with previously described methods. The whole protocol can be conducted in ∼10 d, including isolation and drying of intermediates and products.