Substituted hydroxyhydrocinnamate esters of the formula (I)
##STR1##
where R is alkyl, n is 0 to 2, m is 1 to 4 and A is alkyl, interrupted or
uninterrupted alkylene, alkanetriyl or pentaerythrityl, are prepared by
continuous transesterification of the corresponding lower alkyl mono-ester
with an alkanol or polyol of the formula A-(OH).sub.m. This novel process
comprises continuously introducing into and reacting the reactants in a
heated distillation column reactor having a reaction zone which contains a
solid, heterogeneous transesterification catalyst to form the compound of
formula (I) and the corresponding lower alkanol; separating the products
so formed based on their difference in volatility; and continuously
removing said products from the distillation column at a steady rate,
thereby preventing the reaction mixture from reaching chemical
equilibrium. The continuous reaction results in improved product
throughput and product quality and has a lower residence time, as compared
to known batch-type processes.