well, I used it directly without addition of HCl ,and the acid contain OH group , and the product is highly soluble in water

Use the acid chloride to undergo acethylation, (equimolar ratio) in THF, directly without the need for neutralization of the HCl salt. Then continue reflux for 6 hr. Get red off the solvent, neutralize with sodium carbonate solution and extract you product by chloroform.

so you mean that the fusion temperatur is debend on the acid?

Maybe  you can  take the reaction with higher temperature .use the seal tube !