Zinc Pivalates Research Articles

Organozinc pivalates for modular Cobalt-Catalyzed carbosulfonylation of 1,3-Enynes

Salt-stabilized organozinc pivalates display crucial counterion-effect by OPiv-coordination, which steer an efficient cobalt-catalyzed 1,4-carbosulfonylation of 1,3-enynes with sulfonyl chlorides under simple and mild reaction conditions. Notably, both aryl and alkyl zinc pivalates show superior reactivity compared to conventional halide-supported organozinc reagents, thus providing an expedient access to the preparation of highly functionalized α-allenyl sulfones via cascade C–C/C–S bond formation. Moreover, late-stage modifications of drug-like compounds and facile transformations of the resulting allenes illustrate the synthetic utility of this protocol.

Preparation and Reactions of (1H-Tetrazol-5-yl)zinc Pivalates

The preparation and reactivity of new solid heterocyclic organozinc reagents, namely N-protected (1H-tetrazol-5-yl)zinc pivalates, as storable solids with appreciably air and moisture stability are reported. They are obtained in high yields from protected 1H-tetrazoles by de­protonation using the mixed zinc–magnesium base TMPZnCl·Mg(OPiv)2 (abbreviated as TMPZnOPiv; TMP = 2,2,6,6-tetramethylpiperidyl). Subsequent cross-couplings and copper-catalyzed electrophilic aminations using hydroxylamine benzoates give access to functionalized 1H-tetrazoles while tolerating many functional groups.

Cobalt-Catalyzed Electrophilic Aminations with Anthranils: An Expedient Route to Condensed Quinolines.

The reaction of various organozinc pivalates with anthranils provides anilines derivatives, which cyclize under acidic conditions providing condensed quinolines. Using alkenylzinc pivalates, electron-rich arylzinc pivalates or heterocyclic zinc pivalates produces directly the condensed quinolines of which several structures belong to new heterocyclic scaffolds. These N-heterocycles are of particular interest for organic light emitting diodes with their high photoluminescence quantum yields and long exciton lifetimes as well as for hole-transporting materials in methylammonium lead iodide perovskites solar cells due to an optimal band alignment for holes and a large bandgap.

Practical Ni-Catalyzed Cross-Coupling of Unsaturated Zinc Pivalates with Unsaturated Nonaflates and Triflates.

A practical nickel-catalyzed cross-coupling of (hetero)aryl or alkynylzinc pivalates with various unsaturated nonaflates or triflates is described. Organozinc pivalates allow these cross-couplings to take place with high yields and a low catalyst loading (0.5 mol %). Couplings with ( E)- and ( Z)-alkenyl triflates proceed with retention of configuration.

Cobalt‐Catalyzed Cross‐Couplings between Alkenyl Acetates and Aryl or Alkenyl Zinc Pivalates

CoBr2 (5 mol %) in the presence of 2,2'-bipyridyl (5 mol %) enables electrophilic alkenylations between easily accessible alkenyl acetates or tosylates and various functionalized aryl zinc pivalates at ambient temperature. This cobalt-catalyzed process was further applicable to alkenyl zinc pivalates to provide substituted 1,3-dienes.

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

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

A Robust and Broadly Applicable Cobalt-Catalyzed Cross-Coupling of Functionalized Bench-Stable Organozinc Pivalates with Unsaturated Halides.

We report a robust and broadly applicable CoCl2 -catalyzed cross-coupling between functionalized aryl and heteroaryl zinc pivalates and various electron-poor aryl and heteroaryl halides (X=Cl, Br, I). Couplings with (E)- or (Z)-bromo- or iodo-alkenes proceed with retention of configuration. Also, alkynyl bromides react with arylzinc pivalates providing arylated alkynes.

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

AbstractThe synthesis of various allylic zinc pivalates with excellent thermal stability, ranging from several month to more than two years, is described.

Thermodynamics and vapor formation features of zinc(II) and tin(II) pivalates

Vapor formation of tin(II) and zinc(II) pivalates were studied using the Knudsen effusion method and mass spectrometry analysis of the gas phase. Sublimation of the tin complex is shown to be accompanied by polymerization of the condensed phase, changing its thermodynamic parameters. The vapor formation of zinc pivalate in the presence of trace amounts of water is accompanied by partial hydrolysis of the condensed phase and sublimation of the sample in the form of Zn4O(piv)6 and Zn2piv4. The absolute partial pressures and heats of sublimation of the components of the gas phase above tin and zinc complexes are calculated.

ChemInform Abstract: TMPZnOPiv·LiCl: A New Base for the Preparation of Air‐Stable Solid Zinc Pivalates of Sensitive Aromatics and Heteroaromatics.

AbstractHindered zinc amide (I) provides a fast access to zinc pivalates of a wide range of aromatic and heteroaromatic substrates bearing sensitive functionalities like aldehyde or nitro groups.

TMPZnOPiv•LiCl: A New Base for the Preparation of Air-Stable Solid Zinc Pivalates of Sensitive Aromatics and Heteroaromatics

A wide range of aryl and heteroaryl zinc pivalates bearing sensitive functionalities were prepared by selective metalation using TMPZnOPiv•LiCl, a new hindered zinc amide base. The new zinc reagents are easy-to-handle solids, which maintain their activity almost entirely (>95%) after 4 h of air exposure and smoothly undergo Negishi cross-couplings and reactions with various electrophiles such as Cu(I)-catalyzed acylations and allylations.

ChemInform Abstract: Preparation of Solid Salt Stabilized Functionalized Organozinc Compounds and Their Application to Cross‐Coupling and Carbonyl Addition Reactions.

AbstractNovel zinc pivalates are prepared as is shown for substrates (III) and isolated as stable powders which can be easily handled.