Robinson Annulation 2
Robinson Annulation
Robinson Annulation is an useful organic reaction. This reaction is named after a British chemist Sir Robert Robinson. The term 'annulation 'stands for 'building a ring '. In this reaction, the formation of α, β-unsaturated cyclic ketones from methl vinyl ketones and aldehyde or ketones takes place.
Actually this reaction is a combination of two reactions. One is 'Michael Addition ' and the other is 'Aldol Condensation '.
Robinson Annulation Mechanism
In the first step, Micheal addition takes place to an α,β-unsaturated ketone.
Enolate is formed and tautomerization takes place for further reaction.
Cyclization takes place. That is, aldol condensation reaction to form six-membered cyclic product. Further hydrolysis results in the formation of α,β-unsaturated cyclic ketones
For example 1, consider the following reaction :
Example 1
Mechanism of the Robinson Annulation
The first step in the process is the Michael Addition to an α,β-unsaturated ketone, such as methyl vinyl ketone:
The newly formed enolate intermediate must first tautomerize for the conversion to continue:
The subsequent cyclization via Aldol Addition is followed by a condensation to form a six-membered ring enone:
Example 2
References :
a) C. H. Heathcock, J. E. Ellis, J. E. McMurry, A. Coppolino, Tetrahedron Lett., 1971, 12, 4995.
b) H. Heathcock, C. Mahaim, M. F. Schlecht, T. Utawanit, J. Org. Chem., 1984, 49, 3264.
c) L.G Wade, Organic Chemistry, 1987, 22, 1085.
Robinson Annulation is an useful organic reaction. This reaction is named after a British chemist Sir Robert Robinson. The term 'annulation 'stands for 'building a ring '. In this reaction, the formation of α, β-unsaturated cyclic ketones from methl vinyl ketones and aldehyde or ketones takes place.
Actually this reaction is a combination of two reactions. One is 'Michael Addition ' and the other is 'Aldol Condensation '.
Robinson Annulation Mechanism
In the first step, Micheal addition takes place to an α,β-unsaturated ketone.
Enolate is formed and tautomerization takes place for further reaction.
Cyclization takes place. That is, aldol condensation reaction to form six-membered cyclic product. Further hydrolysis results in the formation of α,β-unsaturated cyclic ketones
For example 1, consider the following reaction :
Example 1
Mechanism of the Robinson Annulation
The first step in the process is the Michael Addition to an α,β-unsaturated ketone, such as methyl vinyl ketone:
The newly formed enolate intermediate must first tautomerize for the conversion to continue:
The subsequent cyclization via Aldol Addition is followed by a condensation to form a six-membered ring enone:
Example 2
References :
a) C. H. Heathcock, J. E. Ellis, J. E. McMurry, A. Coppolino, Tetrahedron Lett., 1971, 12, 4995.
b) H. Heathcock, C. Mahaim, M. F. Schlecht, T. Utawanit, J. Org. Chem., 1984, 49, 3264.
c) L.G Wade, Organic Chemistry, 1987, 22, 1085.
References: : a) C. H. Heathcock, J. E. Ellis, J. E. McMurry, A. Coppolino, Tetrahedron Lett., 1971, 12, 4995. b) H. Heathcock, C. Mahaim, M. F. Schlecht, T. Utawanit, J. Org. Chem., 1984, 49, 3264. c) L.G Wade, Organic Chemistry, 1987, 22, 1085.