Condensing agents, basic activity

Esters, such as those of malonic, acetoacetic or cyanoacetic acids, in which the methylene group is doubly activated, will condense even with ketones. By varying the proportion of aldehyde or ketone to ester, 2 mols. of the former can be made to condense with 1 of the latter, using the basic condensing agents only (4, below). The following will illustrate these points — ... 

Potassium hydride, being more basic and more active than sodium hydride, is suggested for use as a condensing agent in acetoacetic ester, Claisen, Stobbe, and related condensations which proceed with difiSculty. 

On treatment of compounds containing active C-H bonds with 1,3,5-triazine (1), enamines 11 and 12 are usually the first isolable products. In order to isolate such compounds, the reactions are preferably conducted in the absence of a basic condensing agent.18... 

A change in the pK of the molecule by elimination of the acidic enol function and inclusion of basic nitrogen leads to a marked change in biologic activity. That agent, chromonar (13) shows activity as a coronary vasodilator. Alkylation of ethyl acetoacetate with 2-chlorotriethylamine affords the substituted ketoester (10). Condensation with resorcinol in the presence of sulfuric acid affords directly the substituted coumarin (11). 

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