The γ-Alkylation and γ-Arylation of Dianions of β-Dicarbonyl Compounds

Abstract

It is well known that beta-diketones can undergo condensations at the alpha-methylene group with alkyl halides and certain other reagents though the intermediate formation of monoanions. For example, acetylacetone on treatment with an alkali metal or an alkali metal alkoxide or carbonate forms a mono-anion which can be alkylated with alkyl halides. In 1958, Hauser and Harris reported that, if benzoylacetone or acetylacetone is first converted to the dipotassium salt. The salt undergoes alkylation and other carbon-carbon condensations at the terminal methyl group rather than at the methylene group. Rapid alkylation was observed when the salts were treated with benzyl chloride and after acidification, the terminal monobenzylation derivatives were obtained in good yield. Dibenzylation was not observed. In this chapter alkylations of these and other beta-ketones via dianions are surveyed. Other alkylations are also discussed. Arylations are included because alkylation and arylation are methods for directly converting beta-homologs without increasing their functionality. Keywords: gamma-arylation; gamma-alkylation; dianions; beta-carbonyl compounds; acetylacetone; beta-ketones; keto-aldehydes; keto-esters; dicarbonyl compounds; alkyl halides; alkylation; ammonia; experimental procedures