A One-Pot, Asymmetric Robinson Annulation in the Organic Chemistry Majors Laboratory.

• Autores: Kiel E. Lazarski, Alan A. Rich, Cheryl M. Mascarenhas
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 85, Nº 11, 2008, págs. 1531-1534
• Idioma: inglés
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• Resumen

  • The 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 major. To our knowledge, this is the first example of a one-pot enantioselective Robinson annulation in a second-year organic lab setting. Reaction between methyl vinyl ketone and 2-methyl-1,3-cyclohexanedione in the presence of a catalytic amount of (S)-proline results in the formation of the Wieland�Miescher ketone in 75% yield and an 84:16 enantiomer ratio. The product is purified easily by silica gel chromatography, and enantioselectivity is determined by either chiral HPLC or chiral GC. The catalyst used in the reaction, (S)-proline, is an organocatalyst and is moisture- and oxygen-tolerant and nontoxic. Thus the experiment is classified by many to fall within the category of green chemistry.