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In the Laboratory
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The Step-by-Step Robinson Annulation of Chalcone and Ethyl Acetoacetate. An Advanced Undergraduate Project in Organic Synthesis and Structural Analysis
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Lionel Delaude, Jean Grandjean, and Alfred F. Noels
Département de Chimie, Université de Liège, Sart-Tilman par 4000 Liège, Belgium
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August 2006
Vol. 83 No. 8
p. 1225
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| Abstract |
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The Robinson annulation is a three-step process involving a Michael addition followed by an internal aldol condensation and a dehydration. Under appropriate experimental conditions, it is possible to stop the reaction after every step and to isolate the three products separately. This feature is particularly attractive in the frame of an organic chemistry course. It allows students to confirm experimentally the validity of the stepwise mechanism and to obtain a more thorough understanding of the whole process. It also permits them to synthesize a rich set of related molecules that can be compared and characterized through various analytical techniques. Thus, a stoichiometric mixture of chalcone and ethyl acetoacetate was reacted in ethanol. Depending on the quantity of barium hydroxide monohydrate used as catalyst, the reaction time, and the temperature, three different products were obtained. Their full IR, 1H, 13C, COSY, NOESY, and HETCOR NMR spectra are supplied. Examination of the spectroscopic data helps uncover many challenging structural analysis problems. Among them, the diastereoselective formation of chiral centers during the annulation process, the distinction between axial and equatorial substituents on a cyclohexane ring, and the possibility of a keto–enol tautomerism are extensively discussed.
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| Supplement |
Experimental procedures, notes for the instructor, analytical data and detailed conformation analysis of compounds 1–3 together with their full IR, 1H, 13C, COSY, NOESY, and HETCOR NMR spectra, a list of the acquisition and processing parameters for 2D NMR spectroscopy, and CAS registry numbers for all chemicals are available. A commented slideshow presenting the main features of this project is also available.
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 Contents |
Folder JCE2006p1225W containing JCE2006p1225W.doc (Microsoft Word), JCE2006p1225W.ppt (Microsoft PowerPoint), and JCE2006p1225W.key (Apple Keynote).
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| More Information |
Citation |
Delaude, Lionel; Grandjean, Jean; Noels, Alfred F. J. Chem. Educ. 2006 83 1225.
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Keywords |
Catalysis; Chirality / Optical Activity; Conformational Analysis; Diastereomers; Hands-On Learning / Manipulatives; IR Spectroscopy; Laboratory Instruction; NMR Spectroscopy; Organic Chemistry; Second-Year Undergraduate; Stereochemistry; Synthesis; Upper-Division Undergraduate
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History |
Created:
Last Updated: |
6/21/2006
6/30/2006
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| Home > JCE Print > Journal of Chemical Education > Issues >
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1225
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