The optimum condition for preparing o-hydroxybenzaldehyde by oxidating o-cresol in liquid oxygen is as follows: the mole ratio of methanol to o- cresol is 15, the amount of compounded catalysts of Cu(OAc)2 and Co (OAc)2 is 1% of o-cresol, stirring speed is 500 rotation per minute, reaction time and temperature are 10 hours and 80℃respectively, the mole ratio of sodium hydroxide to o-cresol is 3.

Starting from inexpensive phenylbutanol and o-hydroxybenzaldehyde,salmeterol was synthesized via a few steps,which is a unique long-acting selective β2-adrenoreceptor agonist.

The nucleophilic substitution reaction of chloromethylated polystyrene was performed using the sodium salt of p-hydroxybenzaldehyde as the nucleophilic substitution agent via phase-transfer catalysis,and polystyrene with aldehyde groups on its side chains was prepared.

Although good selectivity for p-hydroxybenzaldehyde has been achieved, the use of methanol as the solvent brings an explosion risk in operation and a large amount of NaOH in the solvent has to be neutralized, which are the main disadvantages.

This paper summarizes the recent development in synthesis of hydroxybenzaldehyde,and points out that hydroxybenzaldehyde by catalytic oxidation,chlorination-hydrolysis and indirect electrooxidation from cresol are three promising approaches.