Solid Organozinc Pivalates: A New Class of Zinc Organometallics with Greatly Enhanced Air- and Moisture-Stability

Abstract

Organozinc species are powerful reagents for performing carbon–carbon and carbon–heteroatom bond-forming reactions in the presence of a transition-metal catalyst. However, extended applications of zinc reagents have been hampered by their moderate air- and moisture­-stability. This short review presents our recent developments on the preparation of solid aryl, benzyl, heteroaryl, allyl zinc pivalates and zinc amide enolate reagents with greatly enhanced stability toward to air and moisture.1 Introduction2 Preparation of Organozinc Pivalates2.1 Using Organic Halides as Substrates2.2 Using a Directed Metalation on Functionalized Arenes and Heteroarenes2.3 Preparation of Solid Allylic Zinc Pivalates3 General Reactivity Patterns of Organozinc Pivalates3.1 General Aspects3.2 Transition-Metal-Catalyzed Cross-Couplings3.3 Other Carbon–Carbon Bond-Forming Reactions Using Organozinc Pivalates3.4 Preparation and Reactions of Solid, Salt-Stabilized Zinc Amide Enolates as New, Convenient Reformatsky Reagents4 Conclusion

Generation of Aryl and Heteroaryl Magnesium Reagents in Toluene by Br/Mg or Cl/Mg Exchange

“…The para ‐anisylmagnesium derivative 5 a underwent a Kumada cross‐coupling in the presence of 2 % Pd(OAc) 2 and 3 % SPhos (25 °C, 2 h), producing biphenyl 8 a in 70 % yield. Transmetalation of 5 a with Zn(OPiv) 2 in toluene gave a milky suspension, which reacted with 7 b (25 °C, 15 h) in a Negishi cross‐coupling in the presence of 4 % of PEPPSI‐ i Pr, furnishing the desired product 8 b in 72 % yield (Scheme ).…”

Preparation and reactions of polyfunctional magnesium and zinc organometallics in organic synthesis

“… 33 These organometallic reagents are readily prepared by various methods and produce, after solvent evaporation, solid organozinc species with enhanced air and water stability. 34 Polyfunctional organozinc pivalates underwent Pd-catalyzed cross-couplings with peptidic aryl halides bearing various acidic protons. 35 They proved also very advantageous for performing other transition metal catalyzed cross-couplings.…”

Synthesizing Highly Fluorinated Oligophenyls via Negishi Coupling of Fluoroarylzinc Pivalates

“…To this end, Negishi couplings quickly came into focus -especially after recent advances introduced a variety of briefly air stable organozinc compounds, which could even be weighted under ambient conditions without significant decomposition. [14,15] Aside from these, there have also been reports of coupling fluorinated aryl zincs using pyridines and other heterocycles as electrophiles [16] as well as reactions of fluoroaryl zinc reagents with hexafluorobenzene in a nucleophilic aromatic substitution forming para-substituted terphenyls. [17] However, the selective synthesis of highly fluorinated biphenyls or larger structures is still an issue with much room for improvement.…”