Hydroquinone diester derivatives and the method for producing the same

A method for producing a hydroquinone diester derivative shown by the following formula (1) containing 0.001 to 1% by weight of a catechol diester derivative shown by the following formula (2):

• wherein R1 represents an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group, and each R2 is the same or different and represents an alkyl group, a cycloalkyl group, an aryl group, or a heterocyclic group,
• which method comprises
• (a) reacting a cyclohex-2-ene-1,4-dione derivative shown by the following formula (3):
• wherein R2 is the same as defined above with an acylating agent in the presence of a catalyst at 50 to 120° C.,
• (b) neutralizing the reaction mixture with a base,
• (c) adding a polar solvent comprising water or a mixture of water and water-miscible organic carboxylic acids to the neutralized reaction mixture for adjusting the solvent-system of the mixture to a solvent composition suitable for crystallization of the compound represented by the formula (1), and
• (d) lowering the temperature of the mixture to a temperature not higher than room temperature, without refluxing the mixture, to crystallize the reaction product of the formula (1), and wherein (c) the addition step and (d) the lowering-temperature step are respectively conducted as a single operation.