2-Heptanone lithium 2-enolates

Directed aldol condensation. House et al. have published a detailed procedure for the aldol condensation of the lithium enolate of phenylacetone with n-butyraldehyde in the presence of zinc chloride to give fhreo-4-hydroxy-3-phenyl-2-heptanone. Ether or ether-dimethoxyethane mixtures are the most suitable... 

The present procedures illustrate general methods for the use of preformed lithium enolates5 as reactants in the aldol condensation6 and for the quenching of alkali metal enolates in acetic anhydride to form enol acetates with the same structure and stereochemistry as the starting metal enolate.7 The aldol product, [Pg.55]

Briefly discuss why the reaction of 3,5-diethyl-4-heptanone and lithium diiso-propylamide generates very little enolate even after a few hours at -78°C. 

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