Recent Advances in Cross-Couplings of Functionalized Organozinc Reagents

Cross-couplings involving organozinc reagents require usually a Pd-catalysis (Negishi cross-coupling), however, uncatalyzed cross-couplings of zinc organometallics proceed well in the absence of transition-metal catalysts with reactive electrophiles such as benzal 1,1-diacetates, benzhydryl acetates, and iminium trifluoroacetates. Also, organozinc compounds undergo C-N bond formations with O-benzoylhydroxylamines or organic azides in the presence of cobalt- or iron-catalysts. Besides, highly diastereoselective and enantioselective cross-couplings can be readily performed with room-temperature configurationally stable alkylzinc species producing diastereoselectively and enantiomerically enriched products. Finally, highly regioselective magnesiations of functionalized arenes and heteroarenes undergo Negishi (after transmetalation with ZnCl2) or Cu-catalyzed cross-couplings. 1 Introduction 2 Uncatalyzed Cross-Couplings of Organozinc Reagents with Highly Electrophilic Partners 3 Iron- and Cobalt-catalyzed Aminations Using Organozinc Reagents 4 Stereo- and Regioselective Cross-couplings of Organozinc Reagents 5 Conclusion

Cobalt-Catalyzed Preparation of N-Heterocyclic Organozinc Reagents from Heteroaryl Chlorides

Various substituted and unsubstituted N-heterocyclic chlorides have been converted into their corresponding organozinc species using zinc dust in the presence of zinc pivalate and 10% CoCl2 in benzonitrile at 25 °C. The resulting heteroarylzinc reagents were obtained in 43–98% yield within 9–48 h and reacted with a range of electrophiles, leading to the functionalized heteroarenes.