Rhodium-catalyzed Addition of Aryl- and Alkenylsilanediols to Aldehydes

Abstract

Arylation and alkenylation of aromatic aldehydes with silanediols is shown to proceed by use of a catalytic amount of rhodium complex. Treatment of ethyl(4-methoxyphenyl)silanediol with benzaldehyde in the presence of 3 mol% of [Rh(OH)(cod)]₂ affords 4-methoxyphenyl(phenyl)methanol in 59% yield after stirring at 70 °C for 24 hours. On the other hand, diarylketone was also obtained at elevated temperature via β-hydride elimination from intermediary rhodium alkoxide.

Key words

silanediol - rhodium complex - arylation - alkenylation - aldehyde

References

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8

Experimental: To a mixture of ethyl(4-methoxyphenyl)silanediol(1) (119 mg, 0.6 mmol) and [Rh(OH)(cod)]₂ (4.1 mg, 0.009 mmol) in 2 mL of 1,4-dioxane under argon atomosphere was added 4-methoxybenzaldehyde (0.037 mL, 0.3 mmol). Stirring was continued at 100 °C for 24 h and the resulting mixture was concentrated and subjected to column chromatography on silica gel (hexane-ethyl acetate, 20:1-3:1) to afford 35 mg of bis(4-methoxyphenyl)methanol (47%) and 17 mg of 4,4"-dimethoxybenzophenone (23%). (R_f = 0.22 and 0.35, respectively with Hexane-EtOAc, 3:1).