Diorganozinc

Properties of zinc salts of inorganic and organic salts are Hsted in Table 1 with other commercially important zinc chemicals. In the dithiocarbamates, 2-mercaptobenzothiazole, and formaldehyde sulfoxylate, zinc is covalendy bound to sulfur. In compounds such as the oxide, borate, and sihcate, the covalent bonds with oxygen are very stable. Zinc—carbon bonds occur in diorganozinc compounds, eg, diethjizinc [557-20-0]. Such compounds were much used in organic synthesis prior to the development of the more convenient Grignard route (see Grignard reactions). 

In mosl allylation reactions, only a catalytic amount of CuCN-2LiCl is required [41]. Use of die chiral ferrocenylamine 104 as a catalyst makes enables asymmetric allylation of diorganozinc reagents to be effected witli allylic chlorides iScbeme 2.3G) [78]. Related electropb des such as propargylic bromides [79] and unsaturated epoxides [80] also undergo Su2 -substitution reactions iScbeme 2.37). 

Fimctionalized diorganozinc reagenls [AcOlCHzl jzZn and [ElOzClCHzlijzZn were also employed, giving complete y selectivity in botli cases, witli ees of 5096. 

Structural Studies of Diorganozinc Compounds Bearing a-Bound Ligands 326... 

Well-defined Diorganozinc Compounds in Polyolefin Catalysis 328... 

Diorganozinc Compounds Bearing Monodentate Donor Ligands 332... 

Diorganozinc Compounds Bearing Bidentate Donor Ligands 333... 

Organozinc Cations from the Protonolysis of Diorganozinc Compounds 340... 

Chiral ligands used in addition reactions of diorganozincs with aldehydes 383... 

The simplest diorganozinc compounds, ZnMe2 and ZnEt2, are commercially available from many vendors. All other diorganozinc compounds can be synthesized by one or more of the following synthetic methods, which are detailed in Figure 2 ... 

The utility of the iodine-zinc exchange for the synthesis of diorganozincs having functionalized organic groups is demonstrated by the synthesis of bis(5-pivaloxypentyl)zinc 2 from diethylzinc and 5-iodopentylpivalate.25... 

Functionalized olefins may be converted to the corresponding diorganozinc compounds via hydroboration and subsequent boron-zinc exchange, as shown in Scheme 4.28... 

A more convenient, but less general, synthesis of diorganozincs from olefins is the nickel-catalyzed hydrozincation, shown in Scheme 6. The yields (40-63%) are independent of the amount of diethylzinc added, but dependent on the nature of the olefin. For allylic and homoallylic alcohols and amines, yields as high as 85-95% are possible.32,33... 

Highly efficient syntheses of both hetero- and homoleptic diorganozinc compounds, such as 6 and 7, were achieved by the UV (X > 280 nm) irradiation of mixtures of functionalized organoiodides and diethyl- or diisopropylzinc (Scheme 7).34 Irradiation with ultraviolet light avoids the use of a large excess of diethylzinc, which often furnishes homoleptic diorganozincs rather than the desired heteroleptic ones. Reaction times rarely exceed 2 h and conversions from 55 to 95% were commonly achieved. 

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