Potassium organolithium reagents

Early work has shown that the reaction of simple organolithium reagents with oxiranes lead mainly to products from a- or -deprotonation and not from the desired ring opening reaction. However, some reactions of methyllithium , aUyllithium , aryllithiums" , and vinyllithium/potassium reagents " with oxiranes are reported (Scheme 36). 

Lithium butyldimethylzincate, 221 Lithium sec-butyldimethylzincate, 221 Organolithium reagents, 94 Organotitanium reagents, 213 Palladium(II) chloride, 234 Titanium(III) chloride-Diisobutylalu-minum hydride, 303 Tributyltin chloride, 315 Tributyl(trimethylsilyl)tin, 212 3-Trimethylsilyl-l, 2-butadiene, 305 Zinc-copper couple, 348 Intramolecular conjugate additions Alkylaluminum halides, 5 Potassium t-butoxide, 252 Tetrabutylammonium fluoride, 11 Titanium(IV) chloride, 304 Zirconium(IV) propoxide, 352 Miscellaneous reactions 2-(Phenylseleno)acrylonitrile, 244 9-(Phenylseleno)-9-borabicyclo[3.3.1]-nonane, 245 Quina alkaloids, 264 Tributyltin hydride, 316 Conjugate reduction (see Reduction reactions)... 

Recently, it has been found that one doesn t need to resort to organolithium reagents to generate stoichiometric quantities of silyl anions. Potassium t-butoxide in THE, which is easier to handle than methyllithium, rapidly generates supersilylpotassium from tetrakis(trimethylsilyl)silane, as shown below ... 

Cyclic imines, generated from cyclic N-chloramine precursors by reaction with potassium superoxide in ether solution, react with organolithium reagents to give the corresponding regioselectively alkylated products (Scheme 44). ... 

Heterosubstituted Arenes. As a rule of thumb, the super-basic n-BuLi/f-BuOK reagent having coordinatively saturated lithium preferentially deprotonates such positions where charge excess is most efficiently stabilized. This may result in a different regiochemical behavior with respect to simple organolithium reagents exploiting the so-called optional site-selective metalation. Some representative examples of n-butyllithium/potassium ferf-butoxide metalations of heterosubstituted arenes are shown in Table 5. 

---