Preparation of Solid, Substituted Allylic Zinc Reagents and Their Reactions with Electrophiles.

The treatment of various allylic chlorides or bromides with zinc dust in the presence of lithium chloride and magnesium pivalate (Mg(OCOtBu)2) in THF affords allylic zinc reagents which, after evaporation of the solvent, produce solid zinc reagents that display excellent thermal stability. These allylic reagents undergo Pd-catalyzed cross-coupling reactions with PEPPSI-IPent, as well as highly regioselective and diastereoselective additions to aryl ketones and aldehydes. Acylation with various acid chlorides regioselectively produces the corresponding homoallylic ketones, with the new C-C bond always being formed on the most hindered carbon of the allylic system.