Prepn. of para-hydroxy:phenylacetic acid - by catalytic hydrogenation of racemic para-hydroxy:mandelic acid

摘要

p-Hydroxy phenylacetic acid (I) is prepd. by the hydrogenation of racemic p-hydroxymandelic acid (II): (I) is a known intermediate for pharmaceuticals, esp. beta-blockers, and for phytosanitary products. The process is easier to carry out on an industrial scale than known methods of preparing (I). The reaction is pref. carried out in a water-miscible organic solvent and in the presence of a strong acid. Acetic acid is the pref. solvent, and a protonic acid, esp. HCl, HBr, H2SO4 is usually added. A catalyst Pd on an inert support is usually also present; this may be prepd. by the redn. of Pd++, as its chloride or hydroxide, in the presence of a suspension of the support. Hydrogenation may be effected at atmospheric or elevated pressure.