Preparation of an agar-trapped ionic liquid using as catalyst in the synthesis of xanthene derivatives

Xanthens are one of the important class of organic compounds that are useful intermediates in organic syntheses. Xanthene derivatives are commonly referred to compounds which are used as a class of dyes which includes fluorescein. Using of ionic liquids to catalyze the synthesis of xanthene derivatives lead to cost-saving procedures which minimize the environmental impacts. The concept of gel entrapped base catalysts combines the advantages of alkali and organic bases with those of heterogeneous supports. These are prepared by immobilization of alkali or organic bases by entrapping them in an aqueous gel matrix of agar-agar which is a polymer composed of repeating agarobiose units alternating between 3-linked β-D-galactopyranosyl and 4-linked 3,6-anhydro-α-Lgalactopyranosyle units. Their use helps to reduce the amount of bases used and affords facile separation of products from the catalyst. The gel entrapped base catalysts do not absorb moisture on exposure to air and remain intact. Their use inorganic syntheses also provides excellent opportunity of recyclability and reusability [1, 2]. In this study the preparation of an agar-trapped ionic liquid was investigated. Withentrapping the ionic liquid, we try to decrease the moisturize absorption in the catalyst. After preparation, the agar-trapped ionic liquid was employed as novel catalyst in the synthesis of xanthene derivatives in a straightforward procedure under solvent-free conditions (Scheme 1)