CeCl₃-Catalyzed Reduction of Methyl Esters of Carboxylic Acids to Corresponding Alcohols with Sodium Borohydride

Abstract

A wide range of methyl esters, including esters of aromatic carboxylic acids, alkenyl carboxylic acids, aliphatic carboxylic acids, and protected amino acids, were reduced to the corresponding alcohols with NaBH₄ in ethanol in the presence of a catalytic amount of CeCl₃. The reaction was completed within 24 h at ambient temperature and showed high functional group compatibility and chemoselectivity. With esters containing nitro, methoxyl, halogen, alkenyl, and protected amino functionalities, only the ester group was reduced. The alcohols were isolated after evaporation of the solvent and routine aqueous workup in good yields (75–95%).

Keywords:

• Catalytic reduction
• CeCl₃
• NaBH₄

Notes

^a Reaction conditions: methyl p-nitrobenzoate (1 mmol), NaBH₄ (2 mmol), metallic salts (1 mol%), solvent (5 mL), at room temperature (20–30 °C).

^b Based on HPLC analysis with cinnamyl alcohol as an internal standard.

^a Reaction conditions: ester (1 mmol), NaBH₄ (2 mmol), CeCl₃ · 7H₂O (1 mol%), EtOH (5 mL), 20–30 °C, 24 h.

^b Isolated yields.