Lithium trimethylmagnesate

Ashby and coworkers reported in 1974 stereochemical studies on addition of lithium trimethyhnagnesate to several ketones . The reactions of 4-ferf-butylcyclohexanone with methyllithium, with dimethylmagnesium and with lithium trimethyhnagnesate in ether afforded mixtures of the corresponding axial and equatorial alcohols in ratios of 65 35, 70 30 and 69 31, respectively (equation 11). Reaction of 3,3,5-trimethylcyclohexanone with lithium trimethylmagnesate yielded exclusively the axial alcohol (equation 12). Reaction of norcamphor provided 95% of the endo alcohol and 5% of the exo alcohol (equation 13). In contrast, reaction of camphor yielded the exo alcohol with high stereoselectivity (equation 14). Among the methylmetals examined, no difference in the stereoselectivity was virtually observed. 

Dibromo-compound (50) may be deprotonated with LDA and either alkylated with for example methyl iodide to give compound (51), as shown in eq 32, or treated with different chlorosi-lanes to yield the unsymmetrically substituted dibromodisilyl-methane (52) that may be further converted to the 1,1-disilylethene (53) upon monomethylation with lithium trimethylmagnesate and base-promoted dehydrobromination (eq 33). ... 

---