Scandium(III) Fluoride as a Novel Catalyst for Hydroxymethylation of Dimethylsilyl Enolates in Aqueous Media

Abstract

Hydroxymethylation of dimethylsilyl (DMS) enolates using aqueous formaldehyde solution is catalyzed by scandium(III) fluoride (ScF₃) in aqueous media to give the corresponding β-hydroxy ketones in good to excellent yields. Whilst the DMS enolate reactions are facile the TMS enolates react sluggishly under the same conditions. ScF₃ has been shown to be a unique catalyst for this reaction.

Key words

scandium - scandium fluoride - catalysis - hydroxymethylation - aqueous media

References and Notes

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  Fujita, M.; Nagano, T.; Schneider, U.; Ogawa, C.; Kobayashi, S. unpublished results.

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6

A commercially available HCHO solution including 5-10% MeOH stabilizer was used.

9

Typical Procedure for Hydroxymethylation Reactions: To a solution of ScF₃ (0.03 mmol) in THF-H₂O (2.7 mL/0.22 mL) was added 36% aq solution of formaldehyde (1.5 mmol) and (Z)-dimethyl(1-phenylprop-1-enyloxy)silane (1ab, 0.3 mmol). The reaction mixture was stirred for 40 h at r.t. The mixture was then diluted with H₂O (10 mL), and the aqueous layer was extracted with CH₂Cl₂ (3 × 20 mL). The combined organic extracts were washed with brine, and dried over anhyd Na₂SO₄. After filtration, the solvent was removed in vacuo. The residue was purified by preparative TLC (elution with n-hexane-EtOAc = 3:2) to give 3-hydroxy-2-methyl-1-phenylpropane-1-ono (2a) in 89% yield.