The Crossed Claisen and Related Reactions

Like the aldol reaction, it is sometimes possible to carry out a Claisen reaction with two different carbonyl components as starting materials. [Pg.931]

A crossed Claisen reaction is synthetically useful in two different instances. [Pg.931]

When one ester has no a hydrogens, a crossed Claisen reaction often leads to one product. Common esters with no a H atoms include ethyl formate (HC02Et) and ethyl benzoate (CjH5C02Et). For example, the reaction of ethyl benzoate (as the electrophile) with ethyl acetate (which forms the enolate) in the presence of base forms predominately one p-keto ester. [Pg.931]

The reaction of a ketone and an ester in the presence of base also forms the product of a crossed Claisen reaction. The enolate is always formed from the ketone component, and the reaction works best when the ester has no a hydrogens. The product of this crossed Claisen reaction is a P-dicarbonyl compound, but not a p-keto ester. [Pg.931]

Problem 24.17 What crossed Claisen product is formed from each pair of compounds [Pg.931]

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