Zincates cross-coupling reactions

Treatment of gem-dibromocyclopropane 34 with Bu3ZnLi from —85 to 0°C generates 1-butylcyclopropylzinc 36 via the 1,2-migration of the zincate carbenoid 35 (equation 27)24. Subsequent Pd°-catalyzed cross-coupling reactions afford cyclopropane... 

Like other organozinc reagents65, zincates are excellent nucleophiles in the transition metal catalyzed cross-coupling reaction. Tri- and tetra-arylzincates are reported to... 

Deprotonative zincation and magnesiation have been developed as alternatives for the lithiation of thiophenes. The drawbacks associated with lithiation are that it usually requires the reactions to be performed at —78°C, and the lithium derivatives so formed cannot he directly used for cross-coupling reactions. 

The more difficult cross-coupling reaction between Csp -Csp can be accomplished by mixed zincate compounds, prepared by the reaction of diorganozinc derivatives with Me2CuMgCl-MgCl(CN) (equation 59). Substitution reaction at Csp centers are also efficiently catalyzed by Ni salts when the alkyl halide contains a double bond in remote position (Scheme 22). Changing the double bond for a triple bond leads to an intramolecular carbozincation reaction (equation 60). 

Zincate 120g was generated and used directly in Pd-catalyzed cross-coupling reactions leading to... 

Zinc amide 59 shows better chemoselectivity (but lower reactivity) and leads to the formation of aryl- and heteroarylzinc chlorides. Notably, it can be used to achieve [82] directed ortho- and meta-zincation of functionalized aryl nonaflates, thus providing suitable substrates for further Negishi cross-coupling reactions. 

Applications of Lithium Zincates for Developing New Cross-Coupling Reactions. 193... 

Blair VL, Blakemore DC, Hay D et al (2011) Alkali-metal mediated zincation of N-heterocyclic substrates using the lithium zincate complex, (THF)Li(TMP)Zn( Bu)2 and applications in in situ cross coupling reactions. Tetrahedron Lett 52 4590-4594. doi 10. 1016/j.tetlet.2011.06.090... 

---