Commonly used reagents —- diethylzinc
【English name】 Diethylzinc
【Molecular formula】 C4H10Zn
Molecular weight] 123.51
[CA Registry Number] [557-20-0
[Structural formula] Et2Zn
Physical Properties]] mp -28 oC, bp 118 oC/760 mmHg, bp 27 oC/30 mmHg, d 1.187 g/cm3. soluble in most organic solvents, but reacts violently with water or protonated acidic solutions.
[Preparation and commercial] The reagent is prepared by the reaction of triethylaluminum with zinc chloride [1], or by boron/zinc exchange reaction. The commercial reagents are standard solutions of different solvents and different concentrations, e.g., 1.0 mol/L hexane solution or 1.1 mol/L toluene solution, etc.; the pure reagents can also be stored in metal containers.
The reagent is a highly flammable liquid, spontaneously combusts in air, reacts violently with water, and should be stored in an inert atmosphere. Pure diethylzinc is best diluted with tetrahydrofuran first.
Diethylzinc is a metal-organic reagent and catalyst commonly used in organic synthesis.
I. Nucleophilic addition of diethylzinc to carbonyl compounds
Similar to other dialkyl zinc compounds, the reaction needs to be carried out under anhydrous conditions, the reaction is usually nitrogen or argon as a protective gas. For example, in toluene solution, benzaldehyde reacts with diethylzinc to produce alcohols almost quantitatively, with high optical purity of the product (94% ee) (Eq. 1) [2,3], which can also be used for hydroxyl aldehyde condensation reactions [4].
II. Addition to unsaturated bonds
In the presence of Cu(OTf)2 and appropriate ligands, Et2Zn and its higher homologues readily undergo addition reactions with activated olefins (Eq. 2) [5]. Less active alkynes can also undergo stereospecific addition reactions with diethylzinc catalyzed by CuI (Eq. 3) [6].
In the presence of Cu(OTf)2, Et2Zn undergoes Michael addition reaction with α,β-unsaturated ketones to give highly stereospecific products (Eq. 4) [7,8].
Formation of ternary ring Et2Zn reacts quickly with diiodomethane to form ICH2ZnEt and further (ICH2)2Zn, both of which are well adducted with double bonds to form ternary ring compounds (Eq. 5) [9].
