Cerium(III)-Catalyzed Addition of Diethylzinc to Carbonyl Compounds [1]

Abstract

CeCl₃ catalyzes the addition of Et₂Zn to a variety of alipahtic and aromatic aldehydes and ketones in THF in the presence of TMSCl as a scavenger. Optimization of the applied solvent allowed to avoid the TMSCl mediated addition using CeCl₃·(THF)₂ or Ce(i-PrO)₃ as catalysts. This represents the first application of lanthanide compounds for the addition of Et₂Zn to carbonyl compounds.

Key words

lanthanides - cerium - catalysis - diethylzinc - addition to carbonyls

1

Lanthanides in Organic Synthesis, part 5. For part 4, see
ref. 3b.

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1

Lanthanides in Organic Synthesis, part 5. For part 4, see
ref. 3b.

9

General Experimental Procedure: The reactions were carried out under argon atmosphere using Schlenk techniques. Substances, which are sensitive against moisture and oxidation were stored in a glove box. Reactions were typically performed on a 1.5 mmol scale. In a Schlenk tube 5 mL of solvent were added to the catalyst (usually
0.075 mmol, 0.05 equiv). Then, 3 mL of an 1 M solution of diethylzinc (3 mmol, 2 equiv) in the applied solvent were transferred to the reaction via canulla. To the reaction mixture 1.5 mL of a 1 M solution of aldehyde (1.5 mmol,
1 equiv) in the used solvent were then added slowly by using a syringe pump. When TMSCl was used as a scavenger
1.5 mL of a 1.5 M solution (2.25 mmol, 1.5 equiv) in the chosen solvent were added simultaneously using the same syringe pump. After careful addition of 25 mL of sat. aq NH₄Cl or 2 N HCl, respectively, the aqueous phase was extracted with ethylether (3 × 30 mL). The combined and dried (MgSO₄) organic layers were then liberated from the solvent and purified by flash chromatography eluting with EtOAc/petroleum ether.