The reactions of ketone dilithio α,β-dianions with imines and hydrazones were investigated. The nucleophilic addition reaction to C–N double bonds took place selectively at the β-position of dianions to form lithium Z-enolates containing a lithium amide portion, which is then transformed into γ-amino ketones and related compounds by the subsequent reaction with electrophiles.
The cross-coupling reaction of dianion cuprates, generated from ketone α,β-dianions and copper salts, with acid chlorides, was studied. The reaction gave good to moderate yields of unsymmetrical 1,4-diketones. The consecutive treatment of a dianion cuprate with cyclohexanecarbonyl chloride and methyl iodide or two different acid chlorides gave 2-methyl-substituted 1,4-diketone or triketone, respectively
The conjugate addition of organozincates derived from ketone α,β-dianions to enones was examined. Good yields of unsymmetrical 1,6-diketones were obtained by this reaction. A mixed zincate consisting of the dianion and methyllithium in a 2:1 ratio gave results which were comparable to those of an unmixed dianion zincate.
Chelation-Aided Generation of Ketone α,β-Dianions and Their Use as Copper Ate Complexes. Unprecedented Enolate Intervention in the Conjugate Addition to Enones
Ketone dilithio alpha,beta- and alpha,beta'-dianions can be generated by a tin-lithium exchange reaction of the lithium enolate of beta-tributyltin substituted ketones. A chelation-aided approach, which employs beta-dichlorobutyltin substituted ketones and n-BuLi, is also useful for the generation of ketone alpha,beta-dianions having the Z-geometry at the alkene. The generated dianions can be transformed into substituted ketones by reaction with various carbon electrophiles. (c) 2005 Elsevier Ltd. All rights reserved.