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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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Abstract
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.
Keywords (Audience):
Second-Year UndergraduateKeywords (Domain):
Organic ChemistryKeywords (Pedagogy):
Hands-On Learning / ManipulativesKeywords (Subject):
CatalysisCiting Articles
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This article has been cited by 2 ACS Journal articles (2 most recent appear below).
A One-Pot, Asymmetric Robinson Annulation in the Organic Chemistry Majors Laboratory
Kiel E. Lazarski , Alan A. Rich and Cheryl M. MascarenhasJournal of Chemical Education2008 85 (11), 1531A One-Pot, Asymmetric Robinson Annulation in the Organic Chemistry Majors Laboratory
Kiel E. Lazarski , Alan A. Rich and Cheryl M. MascarenhasJournal of Chemical Education2008 85 (11), 1531The Robinson annulation is a topic of importance in the second-year organic curriculum. A one-pot, enantioselective Robinson annulation is described. The experiment is completed in two lab periods and is geared towards the second-year organic chemistry ...
The Synthesis of N-Benzyl-2-azanorbornene via Aqueous Hetero Diels–Alder Reaction. An Undergraduate Project in Organic Synthesis and Structural Analysis
Xavier Sauvage and Lionel DelaudeJournal of Chemical Education2008 85 (11), 1538The Synthesis of N-Benzyl-2-azanorbornene via Aqueous Hetero Diels–Alder Reaction. An Undergraduate Project in Organic Synthesis and Structural Analysis
Xavier Sauvage and Lionel DelaudeJournal of Chemical Education2008 85 (11), 1538The synthesis of N-benzyl-2-azanorbornene via aqueous hetero Diels–Alder reaction of cyclopentadiene and benzyliminium chloride formed in situ from benzylamine hydrochloride and formaldehyde is described. Characterization of the product was achieved by IR ...
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- Received: August 03, 2009
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