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Robinson annulation



The Robinson annulation is an organic reaction used to create a six-membered ring α,β-unsaturated ketone using a ketone (or aldehyde) and methyl vinyl ketone.[1][2][3] It is named after Sir Robert Robinson, the British chemist who discovered it while he was at the University of Oxford.

In addition to methyl vinyl ketone, 1-chloro-3-propanone[4][5] and isoxazoles[6] will give the same product.

The Wieland-Miescher ketone is the Robinson annulation product of 2-methyl-1,3-cyclohexanedione and methyl vinyl ketone while the Hajos-Parrish ketone is the product of 2-methyl-1,3-cyclopentanedione and methyl vinyl ketone.

Additional recommended knowledge

Contents

Reaction mechanism

Methyl vinyl ketone (or variants thereof) are essential for the annulation as they are simultaneously a Michael acceptor and able to take part in an aldol condensation. The first step in the Robinson annulation (also spelt annelation) is a Michael addition followed by an aldol reaction as the annulation step in the process. The reaction then proceeds as an aldol condensation to make the desired cyclohexenone ring.

Variations

Asymmetric Robinson annulation

The organocatalyst Proline has been used to resolve the enantiomeric isomers of Robinson annulations in asymmetric synthesis. [7]. A proline derivative was employed in an asymmetric annulation of a geranial [8]:

Wichterle reaction

The Wichterle reaction is a variant of the Robinson annulation that replaces methyl vinyl ketone with 1,3-dichloro-cis-2-butene. [9] [10] [11]

Hauser annulation

The reaction sequence in the related Hauser annulation is michael addition - Dieckman condensation - elimination [12]. The Hauser donor is an aromatic methylene sulfoxide or sulfone with a carboxylic ester group in the ortho position. The Hauser acceptor is also a Michael acceptor. In the original Hauser publication ethyl 2-carboxybenzyl phenyl sulfoxide reacts with 3-pentene-2-one with LDA as a base in THF at -78°C [13]:

The original reaction product still contains the sulfoxide group but it is lost on heating in an elimination reaction. The ultimate reaction product is a napthalene derivative. The dual purpose of the sulfoxide group is as stabilizing group for the carbanion in the first reaction step and as leaving group in the second.

References

  1. ^ Rapson, W. S.; Robinson, R.; J. Chem. Soc. 1935, 1285.
  2. ^ Bergmann, E. D.; Gingberg, D.; Pappo, R. Org. React. 1959, 10, 179. (Review)
  3. ^ Gawley, R. E. Synthesis 1976, 777-794. (Review)
  4. ^ Heathcock, C. H.; Ellis, J. E.; McMurry, J. E.; Coppolino, A. Tetrahedron Lett. 1971, 12, 4995.
  5. ^ Heathcock, C. H.; Mahaim, C.; Schlecht, M. F.; Utawanit, T. J. Org. Chem. 1984, 49, 3264. (doi:10.1021/jo00192a004)
  6. ^ McMurry, J. E. Organic Syntheses, Coll. Vol. 6, p.781 (1988); Vol. 53, p.70 (1973). (Article)
  7. ^ Organic Syntheses, Coll. Vol. 7, p.368 (1990); Vol. 63, p.37 (1985). (Article)
  8. ^ Total Synthesis and Revised Structure of Biyouyanagin A K. C. Nicolaou, David Sarlah, and David M. Shaw Angew. Chem. Int. Ed. 2007, 46, 4708 –4711 doi:10.1002/anie.200701552
  9. ^ Wichterle, O. et al. Coll. Czech. Chem. Commun. 1948, 13, 300.
  10. ^ Kobayashi, M.; Matsumoto, T. Chem. Lett. 1973, 957.
  11. ^ Organic Syntheses, Coll. Vol. 5, p.869 (1973); Vol. 45, p.80 (1965). (Article)
  12. ^ Recent Advances in the Hauser Annulation Mal, D.; Pahari, P. Chem. Rev.; (Review); 2007; 107(5); 1892-1918. doi:10.1021/cr068398q
  13. ^ New synthetic methods for the regioselective annelation of aromatic rings: 1-hydroxy-2,3-disubstituted naphthalenes and 1,4-dihydroxy-2,3-disubstituted naphthalenesFrank M. Hauser and Richard P.RheeJ. Org. Chem.; 1978; 43(1) pp 178 - 180; doi:10.1021/jo00395a048
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Robinson_annulation". A list of authors is available in Wikipedia.
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