Organozinc Pivalate Reagents: Segregation, Solubility, Stabilization, and Structural Insights

Abstract

The pivalates RZnOPiv⋅Mg(OPiv)X⋅n LiCl (OPiv=pivalate; R=aryl; X=Cl, Br, I) stand out amongst salt-supported organometallic reagents, because apart from their effectiveness in Negishi cross-coupling reactions, they show more resistance to attack by moist air than conventional organometallic compounds. Herein a combination of synthesis, coupling applications, X-ray crystallographic studies, NMR (including DOSY) studies, and ESI mass spectrometric studies provide details of these pivalate reagents in their own right. A p-tolyl case system shows that in [D8]THF solution these reagents exist as separated Me(p-C6H4)ZnCl and Mg(OPiv)2 species. Air exposure tests and X-ray crystallographic studies indicate that Mg(OPiv)2 enhances the air stability of aryl zinc species by sequestering H2O contaminants. Coupling reactions of Me(p-C6H4)ZnX (where X=different salts) with 4-bromoanisole highlight the importance of the presence of Mg(OPiv)2. Insight into the role of LiCl in these multicomponent mixtures is provided by the molecular structure of [(THF)2Li2(Cl)2(OPiv)2Zn].

Preparation and Application of Solid, Salt‐Stabilized Zinc Amide Enolates with Enhanced Air and Moisture Stability

“…[10] After solvent removal, these organozinc pivalates gave powders that are usually stable for several hours in air and several years under argon. Furthermore, these solid zinc pivalates proved to be versatile reagents for the high-throughput screening of palladium-catalyzed Negishi cross-couplings and generally display the same reactivity as the regular organozinc halides.…”

Cobalt‐Catalyzed Electrophilic Amination of Aryl‐ and Heteroarylzinc Pivalates with N‐Hydroxylamine Benzoates

“…[15] When using iron(II) or copper(I) catalysts,t he main product is the corresponding homodimer (e.g.b iphenyl;T able 1, entries 1-3). [15] When using iron(II) or copper(I) catalysts,t he main product is the corresponding homodimer (e.g.b iphenyl;T able 1, entries 1-3).…”

Preparation of Solid Polyfunctional Alkynylzinc Pivalates with Enhanced Air and Moisture Stability for Organic Synthesis

“…[6] (Hetero)arylzinc pivalates proved to be unique bench-stable solid reagents for cobalt-catalyzed cross-couplings. [8] Further, we have demonstrated the utility of alkynylzinc reagents (1)f or the formation of new carbon-carbon bonds including their participation in 1,3-dipolar cycloadditions without the cleavage of the carbon-zinc bond. [8] Further, we have demonstrated the utility of alkynylzinc reagents (1)f or the formation of new carbon-carbon bonds including their participation in 1,3-dipolar cycloadditions without the cleavage of the carbon-zinc bond.…”