Air-Stable Solid Aryl and Heteroaryl Organozinc Pivalates: Syntheses and Applications in Organic Synthesis

摘要

A wide range of air-stable, solid, polyfunctional aryl and heteroarylzinc pivalates were efficiently prepared by either magnesium insertion or Hal/Mg exchange followed by transmetalation with Zn(OPiv)_2 (OPiv=pivalate). By reducing the amount of LiCl the air stability could be significantly enhanced compared with previously prepared reagents. An alternative route is directed magnesiation using TMPMgCl·LiCl (TMP=2,2,6,6-tetramethylpiperidyl) followed by transmetalation with Zn(OPiv)_2 or, for very sensitive substrates, direct zincation by using TMPZnOPiv. These zinc reagents not only show excellent stability towards air, but they also undergo a broad range of C-C bond-formation reactions, such as allylation and carbocupration reactions, as well as addition to aldehydes and 1,4-addition reactions. Acylation reactions can be performed by using an excess of TMSCl to overcome side reactions of the omnipresent pivalate anion.