Synthesis of novel carboxylated benzoxazolylcoumarins

Coumarins are a family of compounds that have been studied extensively for their practical applications, as textile dyes, optical brighteners, laser dyes, sensitisers in phototherapy, biological labels. Coumarin derivatives have been also used in making fluorogenic enzyme substrates. Disperse dyes containing an electron-donating group, such as N,N-diethylamino, and an heterocyclic residue in position 3 are widely used as optical brighteners for polyester, polyamide and polyvinyl chloride plastics. Several 7-hydroxycoumarins substituted in position 3 are efficient laser dyes and the lasing range is amplified if there is an heterocyclic ring at this position. Recently, we have been working with compounds containing S, N or O heterocycles linked to a benzoxazole. In this paper we report the synthesis of coumarinyl-benzoxazole derivatives with carboxylic groups on the benzoxazole moiety (Fig. 1). This type of compound would enlarge the scope of the potential applications for industrial 9 or biological purposes. 3