[watizit97]

Hello.

I am just wondering whether it is possible to combine the hydroxy group of 4-Hydroxy-1-naphthalenesulfonic acid sodium salt to another compound with -COOH group via esterification?

[wildfyr]

Certainly, should be conventional phebyl ester synthesis.

[hollytara]

The tricky part is likely solubility.  You could use an acid chloride to react with the hydroxyl, but the salt may have limited solubility in the solvents we typically use for reactions of acid chloride + alcohol - you may have to use something more polar like DMF, NMP or DMSO. The salt it is more soluble in water, but esterification is hard to do in water, but it has been done - see Org Lett. 2012 Sep 21; 14(18): 4910–4913.

[rolnor]

You can get a mixed sulphonic-carboxyl anhydrid but it will be easy to hydrolyse in the workup if you add MeOH after the esterification is finnished. You could make a Bu4N+-salt of the startingmaterial if solubility is poor.

[kriggy]

DMF can cause problems when combined with acid chlorides via formation of vilsmayer reagent and futher side reactions. Why dont you use classic esterification conditions using dcc and DMAP in acetonitrile or other solvents? Also, if the salt is not soluble, the reaction can be done in suspension (did that in few cases when my acid chloride was not soluble enough)