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, and the pure reagents can also be stored in metal containers.
[Precautions] 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 hydroxyaldehyde condensation reactions
II. Addition with unsaturated bonds
In the presence of Cu(OTf)2 and appropriate ligands, Et2Zn and its higher homologues are susceptible to addition reactions with activated olefins In CuI-catalyzed reactions, less reactive alkynes can also undergo stereospecific addition reactions with diethylzinc (Eq. 3)[6].
In the presence of Cu(OTf)2, Et2Zn undergoes Michael addition with α,β-unsaturated ketones to give highly stereospecific products
Formation of ternary ring Et2Zn reacts quickly with diiodomethane to form ICH2ZnEt and further to form (ICH2)2Zn, both of which are well adducted to the double bond to form ternary ring compounds
Commonly used reagents —- Triphenylphosphine
[English name] Triphenylphine
Molecular formula] C18H15P
Molecular weight] 262.29
[CA Registry Number] [603-35-0
Structural formula] Ph3P
Physical Properties] bp 337 oC/1.0 mmHg, mp 79~81oC, d 1.18 g/cm3. white crystals, soluble in most organic solvents, insoluble in water; soluble in ethanol, benzene, chloroform; very soluble in ether.
Preparation and commercial products]: Crystallized from hexane, methanol or 95% ethanol; dried over CaSO4 or P2O5 at 65 oC/1.0 mmHg to obtain a pure solid. It is sold by large multinational reagent companies.
Precautions] This reagent can irritate the human body under intense sunlight, and is neurotoxic if exposed for a long time, and is a hazardous material, and cannot be coexisted with strong oxidizing reagents. The reactivity of aryl phosphine with oxygen is lower than that of benzyl and alkyl phosphine. However, air oxidizes triphenylphosphine very significantly, generating triphenylphosphine oxides. Triphenylphosphine is less likely to catch fire and explode, but when it is heated to decomposition, toxic phosphine and POx fumes are produced. Handling should be done in a fume hood.
Triphenylphosphine is a fairly common reducing agent, and in most cases the reaction is driven by the formation of triphenylphosphine oxide (a thermodynamically favorable reaction). In addition, triphenylphosphine is widely used as a ligand for metal catalysts.
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