Aldol Addition

Aldol Addition
Aldol Reaction


'Aldol' is an abbreviation of aldehyde and alcohol. When the enolate of an aldehyde or a ketone reacts at the α-carbon with the carbonyl of another molecule under basic or acidic conditions to obtain β-hydroxy aldehyde or ketone, this reaction is called Aldol Reaction.


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Mechanism





Under conditions of kinetic control, the mixed Aldol Addition can be used to prepare adducts that are otherwise difficult to obtain selectively. This process begins with the irreversible generation of the kinetic enolate, e.g. by employing a sterically hindered lithium amide base such as LDA (lithium diisopropylamide). With an unsymmetrically substituted ketone, such a non-nucleophilic, sterically-demanding, strong base will abstract a proton from the least hindered side. Proton transfer is avoided with lithium enolates at low temperatures in ethereal solvents, so that addition of a second carbonyl partner (ketone or aldehyde) will produce the desired aldol product.



Recent Literature


Highly Enantioselective Organocatalytic Direct Aldol Reaction in an Aqueous Medium
V. Maya, M. Raj, V. K. Singh, Org. Lett., 2007, 9, 2593-2595.


A Highly Efficient Organocatalyst for Direct Aldol Reactions of Ketones with Aldedydes
Z. Tang, Z.-H. Yang, X.-H. Chen, L.-F. Cun, A.-Q. Mi, Y.-Z. Jiang, L.-Z. Gong, J. Am. Chem. Soc., 2005, 127, 9285-9289.


The First Direct and Enantioselective Cross-Aldol Reaction of Aldehydes
A. B. Northtrup, D. W. C. MacMillan, J. Am. Chem. Soc., 2002, 124, 6798-6799.


Highly Diastereo- and Enantioselective Direct Aldol Reactions in Water
Y. Hayashi, T. Sumiya, J. Takahashi, H. Gotoh, T. Urushima, M. Shoji, Angew. Chem. Int. Ed., 2006, 45, 958-961.


Combined Proline-Surfactant Organocatalyst for the Highly Diastereo- and Enantioselective Aqueous Direct Cross-Aldol Reaction of Aldehydes
Y. Hayashi, S. Aratake, T. Okano, J. Takahashi, T. Sumiya, M. Shoji, Angew. Chem. Int. Ed., 2006, 45, 5527-5529.


Chiral Diols: A New Class of Additives for Direct Aldol Reaction Catalyzed by L-Proline
Y. Zhou, Z. Shan, J. Org. Chem., 2006, 71, 9510-9512.


The Aldol Reaction under High-Intensity Ultrasound: A Novel Approach to an Old Reaction
G. Cravotto, A. Demetri, G. M. Nano, G. Palmisano, A. Penoni, S. Tagliapietra, Eur. J. Org. Chem., 2003, 4438-4444.


Reconstructed Hydrotalcite as a Highly Active Heterogeneous Base Catalyst for Carbon-Carbon Bond Formations in the Presence of Water
K. Ebitani, K. Motokura, K. Mori, T. Mizugaki, K. Kaneda, J. Org. Chem., 2006, 71, 5440-5447.


Direct Asymmetric Aldol Reactions of Acetone Using Bimetallic Zinc Catalysts
B. M. Trost, E. R. Silcoff, H. Ito, Org. Lett., 2001, 3, 2497-2500.


Development of Highly Diastereo- and Enantioselective Direct Asymmetric Aldol Reaction of a Glycinate Schiff Base with Aldehydes Catalyzed by Chiral Quaternary Ammonium Salts
T. Ooi, M. Kameda, M. Taniguchi, K. Maruoka, J. Am. Chem. Soc., 2004,126, 9685-9694.


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