Abstract
A new practical method for ketalization or oxy-Michael/ketalization was developed using the high-pressure-promoted condensation of ketones or α,β-unsaturated ketones with alcohols in the presence of trialkyl orthoformates as water scavengers.
Key words
ketalization - ketones - enones - trialkyl orthoformates - high-pressure reaction
References
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General procedure
A mixture of ketone and trimethyl orthoformate (2 equiv) in MeOH was placed in a Teflon reaction vessel (2.0 mL volume), and the mixture was allowed to react at 0.8 GPa at the appropriate temperature and for the specified time (Table
[1]
). After the mixture was cooled and the pressure was released, the mixture was concentrated in vacuo. The crude product was purified quickly by column chromatography on alumina (elution with hexane-Et2O) to afford the pure product in good to excellent yields.
8 The use of a stoichiometric amount of this reagent resulted in incomplete conversion.
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14 These reactions were best performed in CH2Cl2 using trimethyl orthoformate (2 equiv) and MeOH (2 equiv).
The acid- or base-catalyzed conjugate addition reaction of alcohols to enones under high pressure is known:
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See also:
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