Esters and orthoesters as alkylating agents at high temperature. Applications to continuous-flow processes
At high temperature (180–200 °C) esters, orthoesters, carbonates and orthocarbonates have been found to alkylate acidic compounds via a BAl2, mechanism. Phenol gives anisole with methyl acetate in the presence of potassium carbonate. Thiols and other CH-acidic compounds are also alkylated under such conditions.
The results obtained under batch conditions can be repeated under continuous-flow conditions, if the base which promotes the reaction can be used in catalytic amount. Continuous-flow alkylation of thiophenol by methyl acetate on a sodium acetate-type fixed bed, and other alkylations by orthoesters or orthocarbonates on a potassium carbonate catalytic bed, have been achieved.