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

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. Reactive but stable: The preparation of polyfunctional, air‐stable, solid aryl and heteroaryl organozinc pivalates by either Mg insertion or Hal–Mg (Hal=Br, I) exchange, followed by transmetalation with Zn(OPiv)2 (OPiv=pivalate) or alternatively by directed metalation is described. The zinc reagents show excellent stability in air (up to 4 h at 25 °C) and undergo a range of reactions including allylation, acylation, and carbocupration reactions, additions to aldehydes, and 1,4‐addition reactions (see scheme).