Metals organozincs

Microwave-assisted High-temperature Metalation of Weakly Activated Aromatics and Heteroaromatics. Over the last few decades, microwave irradiation has been used to accelerate numerous organic reactions, including metalations. Organozinc reagents of the type RZnX possess a good thermal stability and tolerate functional groups, even at elevated temperatures. The direct zincation of coumarin requires 7 days at room temperature to achieve 85% conversion. However, under microwave irradiation, the zincation was achieved in over 90% yield (80 °C, 1 h) (eq 7). ... 

By reaction of an a-halo ester 1 with zinc metal in an inert solvent such as diethyl ether, tetrahydrofuran or dioxane, an organozinc compound 2 is formed (a Grignard reagent-like species). Some of these organozinc compounds are quite stable even a structure elucidation by x-ray analysis is possible in certain cases ... 

The Reformatsky reaction is a classical reaction in which metallic zinc, an a-haloester, and a carbonyl compound react to give a (i-hydroxyester.162 The zinc and a-haloester react to form an organozinc reagent. Because the carboxylate group can stabilize the carbanionic center, the product is essentially the zinc enolate of the dehalogenated ester.163 The enolate effects nucleophilic attack on the carbonyl group. 

Tmnsithn Metals magnesium, organozinc, and organocopper reagents. We then proceed to arylation of... 

Organozinc compounds are more reactive nucleophiles requiring no activation for the trans-metalation step, while allowing for much wider functionality to be present in the molecule than in organomagnesium compounds. However, organozinc compounds cannot be stored without special precautions, and therefore should be generated immediately prior to use, which makes... 

Organozinc Halides by Transition Metal-catalyzed Reactions 330... 

Organozinc Compounds with Metal-Metal Bonds 381... 

Organozinc Compounds with a Direct Zinc-Metal Bond 382... 

Metal-catalyzed cross-coupling reactions between organozinc derivatives and alkyl halides 405... 

Metal-catalyzed cross-coupling reactions of organozinc derivatives with aryl and vinyl halides 408... 

Despite the extensive history of organozinc chemistry, the first solid-state structure of a Lewis base-free diorganozinc compound with cr-bound ligands, namely diphenylzinc, was not reported until 1990.37 Diphenylzinc was synthesized by the transmetallation of diphenylmercury with metallic zinc (Scheme 10) and, after multiple sublimations, obtained halide free in 67% yield. 

Zinc compounds have recently been used as pre-catalysts for the polymerization of lactides and the co-polymerization of epoxides and carbon dioxide (see Sections 2.06.8-2.06.12). The active catalysts in these reactions are not organozinc compounds, but their protonolyzed products. A few well-defined organozinc compounds, however, have been used as co-catalysts and chain-transfer reagents in the transition metal-catalyzed polymerization of olefins. 

Heterobimetallic clusters (Figure 58,125 and 126) with solvent-dependent structures were also obtained upon mixing alkali metal tert-butoxides and -trimethylsiloxides in THF, TMEDA, and toluene.184 The common occurrence of heterocubes shows that there is a strong driving force for the formation of heterocubic structures in organozinc alkoxides. Solvent effects are important, however, as demonstrated by the formation of seeo-diheterocubic compounds in TMEDA. 

The report by Resa et al. on a hydrocarbon-soluble, molecular compound of monovalent zinc, namely decamethyl-dizincocene, therefore caused considerable excitement among inorganic and organometallic chemists alike.233 Organozinc compounds with direct zinc-transition metal bonds have also been reported recently, and this area of organozinc chemistry with direct metal-metal bonds will undoubtedly witness considerable growth in the near future. 

The report of the first zinc compound with a Zn-Zn core elicited a number of critical comments on the structure and bonding of decamethyldizincocene, and the interpretation of the results.236,237 None of the authors of these commentaries questioned the data or their interpretation. Parkin, however, has pointed out that the formal oxidation state of +1 for zinc in this compound is merely due to the convention that metals are assigned an oxidation state of 0 when they form bonds with like atoms.237 If the conventional definition of valence, namely the capacity of atoms to form bonds to other atoms is used, then the zinc atoms in decamethyldizincocene are not monovalent, but divalent. The synthesis of a paramagnetic organozinc compound in which zinc uses only one of its two 4s electrons will remain an interesting challenge to many synthetic organometallic chemists. 

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