Nanocrystalline-cellulose-supported acidic ionic liquid carrying SO3H functional group was prepared using nanocrystalline cellulose, imidazole and 1,4-butane sultone as the source chemicals. The prepared nanocrystalline-cellulose-supported ionic liquid catalyst was characterized by AFM and SEM and its catalytic activity in the reaction of resorcinol with ethyl acetoacetate was tested in a solvent-free condition. The effects of reaction time, reaction temperature, and the ratio of catalyst on the conversion of resorcinol were investigated. A variety of coumarin derivatives were obtained in good yield in the absence of solvent. 1. Introduction Coumarins are very significant heterocyclic compounds in organic synthesis. These compounds are known as benzo-2-pyrone derivatives which are principally found in plants. Most of coumarin derivatives show some useful bioactivities. These compounds are widely used for pharmaceutical and agricultural applications and fragrance [1]. The Pechmann reaction is one of the most valuable methods for synthesis of coumarin which starts by phenols and acidic catalysts like concentrated sulfuric acid and Bronsted acidic ionic liquid [2]. Moreover, some other harsh catalysts used in the Pechmann reaction are InCl3, ZrCl4, Yb(OTF)3, and p-TSOH [3]. These methods have some disadvantages such as by-products formation, long reaction time, and corrosion problems. So, there have been some attempts to find optional and safe synthetic routes [4]. However, most of these methods also suffer from problematic conditions such as expensive reagent, durable workup, large amount of support, or a catalyst which makes large amount of toxic waste. Therefore, with considering these problems, we tried to introduce a new ecofriendly catalyst to promote the Pechmann reaction. Obviously, heterogeneous catalysts such as solid phase supported catalysts are particularly attractive for synthesis of chemical compounds because they allow simple separation of catalyst from the reaction mixture and prevent the release of toxic material to the environment. In recent years science of catalysts is shifting to reusable resources and ecofriendly processes. Thus, biodegradable and biocompatible polymers are appropriate alternatives in serving on the catalytic field [5, 6]. Among the biopolymers, cellulose and its derivatives are extensively used in chemicals and bioapplications. They are also applied as support for synthesis of organic compounds because cellulose and its derivatives are biodegradable, environmentally safe, widely abundant in nature, and easy to
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