To provide a compound which is stable in an alkali hydrolysis condition, can rapidly regnerate an acidic proton-bearing compound or its dissociation product, when a nuclophilic group is introduced to a specific position in the molecule, and is effective as a blocking agent for the acidic proton-bearing compound.

A naphthol compound of general formula (I) [A is the residue of the acidic proton-bearing compound (AH) having a pKa of 0 to 14; R1 is an aliphatic group, an aryl group or a heterocyclic group; R2 is a substituent; (n) is an integer of 0 to 5; X is H, a halogen atom, R11, R11O, R11S, R11OCOO, R12COO, R12(R13)NCOO, R12CON(R13), NO, NO2 or N=N-R11; Y is oxygen atom or sulfur atom; R11 is an aliphatic group, an aryl group or a heterocyclic group; R12 and R13 are each H, an aliphatic group, an aryl group or a heterocyclic group].