ERIC Number: EJ1073075
Record Type: Journal
Publication Date: 2015-Aug
Abstractor: As Provided
Reference Count: 10
"N"-Heterocyclic Carbene-Catalyzed Reaction of Chalcone and Cinnamaldehyde to Give 1,3,4-Triphenylcyclopentene Using Organocatalysis to Form a Homoenolate Equivalent
Snider, Barry B.
Journal of Chemical Education, v92 n8 p1394-1397 Aug 2015
In this experiment, students carry out a modern organocatalytic reaction using IMes·HCl and NaOH to catalyze the formation of 1,3,4-triphenylcyclopentene from cinnamaldehyde and chalcone in water. Deprotonation of IMes·HCl with NaOH forms the "N"-heterocyclic carbene IMes that reacts with cinnamaldehyde to form a homoenolate equivalent of cinnamate, which undergoes a conjugate addition to chalcone followed by an intramolecular aldol reaction to form a cyclopentane. Formation of a ß-lactone and decarboxylation leads to 1,3,4-triphenylcyclopentene. This reaction introduces students to both organocatalysis and the use of carbonyl anion and homoenolate equivalents in synthesis. This novel and interesting chemistry was first reported in 2006, and the reaction was modified to be carried out in water under an air atmosphere in 2013. The very nonpolar product is easily purified chromatographically. The aliphatic protons form a somewhat complex pattern due to allylic and homoallylic coupling, but with no overlap, so that students can simulate the spectrum perfectly using Web-based software. This experiment can be combined with one of the four preparations of IMes·HCl reported in this Journal, which all use IMes as a ligand rather than an organocatalyst.
Descriptors: Science Instruction, Science Experiments, Scientific Concepts, College Science, Organic Chemistry, Hands on Science, Spectroscopy, Computer Assisted Instruction, Science Laboratories, Laboratory Experiments
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Publication Type: Journal Articles; Reports - Descriptive; Guides - Classroom - Teacher
Education Level: Higher Education; Postsecondary Education
Authoring Institution: N/A
Identifiers - Location: Massachusetts