Mild acetalisation of mono and dicarbonyl compounds catalysed by titanium tetrachloride.Facile synthesis of #beta#-keto enol ethers

摘要

The use of TiCl_4,as a catalyst for the acetalisation, at room temperature,of carbonly compounds is reported.Cyclic ketones and cyclic 1,4-diketones easily afford dimethyl acetals,but cyclic 1,3-diketones give #beta#-keto enol ethers.Additionally,aryl ketones and acyclic ketones failed to react.#beta#-keto aldehydes can be monoprotected either as #beta#-keto enol ethers or #beta#-keto dimethyl acetals depending on the reaction time and catalyst amount.Some mechanistic features are accounted for.