Ketone dilithio dianions

III. REACTIONS OF KETONE DILITHIO DIANIONS A. Single C-C Bond-forming Reactions... 

Chemistry of ketone dilithio dianions TABLE 5. Reaction of dianionic zincates with enone derivatives... 

Ketone dilithio-c /S-dianions (30, formed by treatment of /3 -stannylketones, RCOCH2-CH2SnBuCl2, with 4 equiv. of BuLi) react with imines and hydrazone selectively at the /3-anion portion to give dilithium enolate amides (31).82 Subsequent reaction with electrophiles gives y-amino ketones and related heterocycles. 

The reactions of ketone dilithio ,/i-dianions with imines and hydrazones have been investigated.77 The nucleophilic addition reaction to C—N double bonds took place selectively at the -position of dianions to form lithium (Z)-enolates containing a lithium amide portion, which is then transformed into y-amino ketones and related compounds by the subsequent reaction with electrophiles. 

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... 

Cohen and coworkers reported on dilithio species of ketone ,/ -dianions, in which cyclopropyllithium constitutes the / -carbanion portion10. In the examples given in Scheme 9, the first lithium enolate was produced by proton-abstraction with lithium 2,2,5,5-tetramethylpiperidide (LTMP), and the second involved the reductive cleavage of the carbon-sulfur bond by lithium 4,4 -di-tczt-butylbiphenylide (LDBB). 

Cyclic ketone dianions obtained by the condensation of 1,4-dilithio-1,3-dienes with carbon monoxide can be used for the one-pot synthesis of a variety of 3-cyclopentenone derivatives20. Treatment of the dilithio species with 2 equivalents of benzyl bromide gave the corresponding 2,5-dibenzyl 3-cyclopentenone in 73% yield. A single-crystal structure analysis revealed that the two benzyl groups are in a trans orientation. Several examples of the one-pot synthesis of 3-cyclopentenone derivatives using this method are summarized in Table 7. 

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