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CHEM 125A: FRESHMAN ORGANIC CHEMISTRY II - Lecture 36 - Professor J. Michael McBride
α-Reactivity and Condensation Reactions
As in many synthetic procedures, an important challenge in ketone alkylation is choosing reagents and conditions that allow control of isomerism and of single vs. multiple substitution. β-Dicarbonyl compounds allow convenient alkylation and preparation of ketones and carboxylic acids. The aldol condensation, in which an α-position adds to a carbonyl group to generate a β-hydroxy- or an α,β-unsaturated carbonyl compound, can be driven to completion by removal of water. The Robinson annulation reaction is an important example of conjugate addition to α,β-unsaturated carbonyl compounds. α-Acylation of esters as in the Claisen condensation is a key step in the biosynthesis of fatty acids. Determining the constitutional structure of sugars posed a daunting challenge to early carbohydrate chemists.
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