The chemistry of dianion-type zinc ate complexes

Abstract

Tools for chemo-. regio- and stereo-selective introduction of various functional groups onto organic molecules are still quite limited in their applicability. Our new approaches to functionalizing organic compounds by means of development of the chemistry of dianion-type zinc ate complexes are described. Reactivity and selectivity of tetra-coordinated dianion-type zincates have been ignored for a long time. Halogen-zinc exchange reaction on aromatic rings and silylzincation of terminal alkynes (and alkenes) using dianion-type zincates followed by electrophilic trapping proved a powerful tool for C-C bond formations. The functionalized aromatic or aliphatic zincatc intermediate was also found to undergo copper- and palladium-catalyzed C-C bond-forming reactions with good yields and high chemoselectivity. On the other hand, a sharp difference in regioselectivity in the epoxide-opening reaction between monoanion-type and dianion-type zincates was disclosed. These results clearly suggest that these dianion-type zincates should be distinguished from ordinary tri -coordinated monoanion-type zincates in terms of structure, reactivity, and selectivity, and hence they would open a new window in synthetic organic chemistry.