Butene diol and acetic anhydride reaction mechanism

The esterification reaction is for the alcohol, and the negative electrical density is highly nucleophilic.The electron optic effect of the first esterification after the second esterification activity is reduced

Please help me to explain that the reason urgently needs to understand.

If it is a problem that I want to solve the acylation reaction, I don't know how the reaction you specifically do, the acetic anhydride is excessive, and there is a pyridine solvent, this double acetylation should have no difficulty, and then don'tThere is no problem with the DMAP catalysis.If your feed and operation have no problem, it is not good to explain your strangeness from the mechanism, or it is from the perspective of electron-induced effect, or after a acetyl, the double button forms a smooth structure.One of these configurations can easily form the hydrogen bonding effect of the ester group and the other side of the hydroxyl group, and reduce the reaction activity of the hydroxyl group.