The Preparation of New C(α)-Dianions

Abstract

For more than a decade, Hauser et. al. carried out rather extensive investigations on the preparation and reactions of the multiple anions of β -diketones and related materials. Once the conditions for the preparation of a particular multiple anion seemed established, three reactions were usually attempted with the new multiple anion: alkylations with reagents such as benzyl chloride², Aldol-type condensations with aldehydes or ketones³ such as benzaldehyde and benzophenone, and Claisen-type condensations with esters such as methyl benzoate⁴. Other electrophilic reagents, such as nitriles⁵ and isocyanates⁶, were also condensed with certain of these multiple anions in selective situations; however, the alkylations, acylations, and carbonyl additions received the greatest amount of attention⁷. In some cases only one of the three types of reactions (Aldol) worked well⁸; however this did not mean that conditions could not be found for the other two reaction types. In addition, the synthetic potential of these multiple anion reactions was quite extensive (Scheme 1).