Application of 1,3-azomethine ylides derived from α-dicarbonyl compounds and L-proline to the synthesis of pyrrolizidines

✍ Scribed by Fulvia Felluga; Cristina Forzato; Patrizia Nitti; Giuliana Pitacco; Ennio Valentin; Ennio Zangrando

• Publisher: Journal of Heterocyclic Chemistry
• Year: 2010
• Tongue: English
• Weight: 287 KB
• Volume: 47
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.371

✦ Synopsis

Abstract

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The reaction of 2,3‐butanedione, ethyl pyruvate, and phenylglyoxal with β‐nitrostyrene and L‐proline in isopropanol at room temperature gives substituted pyrrolizidines, as a result of one‐pot three component reaction. On the contrary, a spiropyrrolizidine is formed from 1,2‐cyclohexanedione only when the reaction is carried out in refluxing isopropanol, whereas at room temperature, incorporation of the amine component into the products is not observed and bicyclo[3.2.1]octanones are formed, as a result of a tandem Michael‐Henry reaction. In this latter case, L‐proline acts as an organocatalyst, although with modest enantioselectivity. The stereochemistry of the products is given and the mechanism of formation of products is postulated, on the basis of stereochemical arguments. J. Heterocyclic Chem., (2010).