Patent ID: 8569500
Filing Date: 2013-10-29
Classification: C07C,C07D,C07F,C09B

Abstract:
1. A process for preparing a rylenetetracarboxylic dianhydride, or a salt thereof having formula Ib wherein R is phenoxy, phenylthio, pyridyloxy, pyrimidyloxy, pyridylthio or pyrimidyl-thio, each of which may optionally be mono- or polysubstituted by C m is 1 or 2; n is 4 when m=1; 4 or 6 when m=2, the process comprising a) subjecting a rylenetetracarboximide of general formula II wherein R, m and n are as defined above and R′ is hydrogen or a C to a hydrolysis under alkaline conditions in the presence of a polar organic solvent and removing the rylenetetracarboxylic dianhydride Ib from any rylenetetracarboxylic monoimide monoanhydride of formula Ia which is formed where R′, R, n and m have the same meanings as above, to form the rylenetetracarboxylic dianhydride, or the salt thereof having formula Ib or b) hydrolyzing the rylenetetracarboximide of general formula II under conditions that form the compound of formula Ib and substantially no rylenetetracarboxylic monoimide monoanhydride of the formula Ia.