This chapter is concerned with the reactions of metal salts (enolates) of active methylene compounds with alkylating agents such as alkyl halides to produce allyl derivatives. The first example of this reaction is found in the literature when Geuther prepared ethyl alpha-ethyl acetoacetate by the reaction of the sodium enolate of ethyl acetoacetate with ethyl iodide. The active methylene compounds considered in the chapter include malonic esters, cyanoacetic esters, malonitriles, monocarboxylic esters and mononitriles. These classes of compounds are characterized by the presence of one or more acidic hydrogen atoms attached to carbon. Only C-alkylation has been observed with active methylene compounds and are discussed here. Several alternative methods for the preparation of alkyl and aryl derivatives of carboxylic esters and nitriles have been included.