Enantioselective Hydrophosphonylation of Aldehydes Using an Aluminum Binaphthyl Schiff Base Complex as a Catalyst

Abstract

An aluminum binaphthyl Schiff base complex was found to be an efficient catalyst for enantioselective hydrophosphonylation of aldehydes. High enantioselectivities were obtained in reactions of both aromatic and aliphatic aldehydes (up to 84% and 86% ee, respectively).

Key words

aluminum - asymmetric catalysis - binaphthyl Schiff bases - hydrophosphonylation - α-hydroxy phosphonate

References and Notes

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7

Complexes 2 were prepared according to the reported procedure (ref. 4).

9

Typical Procedure: Hydrophosphonylation of p -Chloro-benzaldehyde
Complex 2e (8.2 mg, 10 µmol) was placed in a flask under nitrogen and THF (0.5 mL) and dimethyl phosphite (10.1 µL, 0.11 mmol) were added. After stirring for 10 min at r.t., p-chlorobenzaldehyde (14.1 mg, 0.1 mmol) was added. After stirring for another 3 d, the reaction was quenched with 1 N HCl and extracted with EtOAc. The organic extract was dried over anhyd MgSO₄ and concentrated. Silica gel chromatography of the residue (hexane-EtOAc, 7:3 to 1:1) gave the desired product (19.5 mg, 78%) as an oil. The ee of the product was determined to be 84% by HPLC using chiral stationary phase column as described in the footnote to Table [1] .