Patent ID: 7872148

Claim:
A process which comprises the steps of: reacting 1,2,3,4-cyclobutanetetracarboxylic acid-1,2:3,4-dianhydride represented by formula [1] wherein R 1 and R 2 each independently denotes a hydrogen atom, a halogen atom, a C 1-10 alkyl group, a C 1-10 halogenated alkyl group, a C 3-8 cycloalkyl group, a phenyl group, or a cyano group with a dialkyl sulfate represented by the formula [7] R 3 2 SO 4 [7] wherein R 3 denotes a C 1-10 alkyl group in the presence of a base catalyst, thereby producing cis, trans, cis-1,2,3,4-cyclobutane tetracarboxylic acid tetraester represented by the formula [3] wherein R 1 , R 2 , and R 3 are as defined above; converting the compound of the formula [3] into the compound of the formula [4] converting the compound of the formula [4] into the compound of the formula [5] and converting the compound of the formula [5] into the compound of the formula [6] thereby producing 1,2,3,4-cyclobutanetetracarboxylic acid-1,3:2,4-dianhydride.