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Abstract
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Organic and biological based solid acids are one of the most applicable compounds which have been used for acid-promoted processes and chemical methodologies. Solid acids have received great attention as a general material for a variety of chemical processes because of their reasonable properties such as nonmetallic, nontoxic, with no generated hazardous waste, reusability and high turnover [1-3]. These compounds have great attention for the past decades due to their advantages such as (i) commercial availability, (ii) identical acidic sites, (iii) water stability, (iv) low cost (v) substrate and functional group selectivity, (vi) recycle and reusability and (vii) easy separation from the reaction mixture [4]. In this work, synthesis and characterization of a new glycoluril tetrakis(butane-1-sulfonic acid) (GTBSA), as a novel nanostructure catalyst with alkane sulfonic acid pending groups will be reported. Also, we present an efficient and green catalyzed MCR towards the synthesis of mono and bis-spiropyrans via one-pot condensation of isatine and other components in refluxing water
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