Microwave-Assisted Clauson-Kaas Synthesis: A Green Approach to Substituted Pyrroles

Abstract

<p>The Clauson-Kaas pyrrole synthesis involving the reaction of primary amines with 2,5dialkoxytetrahydrofurans is traditionally carried out in refluxing acetic acid for periods of hours to days. The extension to less activated nitrogen nucleophiles such as amides and sulfonamides often necessitates the use of an acidic promoter such as phosphorus pentoxide, thionyl chloride or triflic acid. We find that under microwave conditions, the preparation of N-substituted pyrroles can be effected (5-10 min) in green conditions using water or acetic acid. Furthermore, we compare our method with a previously published solventless microwave approach using montmorillonite K10 clay. The ease and efficiency of this process indicates this heterocyclic ring synthesis is well suited for adaptation in an undergraduate laboratory setting demonstrating the use of microwaves in a green heterocyclic ring forming reaction.</p><p>This presentation occurred at the Wright State University Campus-Wide Celebration of Research, Scholarship and Creative Activities on April 16, 2010</p>