Ketone dilithio dianions generation

Ketone dilithio a,ft-dianion species (74) have been generated by the tin-lithium exchange reaction of the lithium enolate of /3-tributyltin-substituted ketones.291 Reaction with carbon electrophiles gives substituted ketones. 

Ketone dilithio a,f - and a -dianions have been generated by a tin-lithium exchange reaction of the lithium enolate of /3-tributyltin-substituted ketones.30 A chelation-aided approach, which employs /S-dichlorobutyltin-substituted ketones and n-BuLi, has been used for the generation of ketone a, f) -dianions having the Z-geometry at the alkene. The generated dianions have been transformed into ketones... 

The simplest dilithio species of ketone a,/ -dianions appeared in 1991 and was reported by Ryu, S onoda and their coworkers11. They found that readily accessible ft -tributylstanny 1 ketones and ft-dichlorobutylstannyl ketones serve nicely as precursors for dianions12,13. Recent work demonstrated that the vinylogous extension of ketone a,ft -dianions can lead to the generation of ketone a,5-dianions14. 

Kowalski and coworkers reported that lithium enolates of a-bromo ketones can be converted to the corresponding ketone dilithio a,a-dianions by Li—Br exchange with r-BuLi (Scheme if. To generate lithium enolates of a-bromo ketones, either method A or B can be used deprotonation of a-bromo ketones by one equivalent of lithium hexamethyldisilazide (LHMDS) (method A) or deacetylation of enol acetates of a-bromo... 

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