Preparation of 2,3,3′,4′ -biphenyltetracarboxylic acid tetraester
View Patent ↗2,3,3′,4′-Biphenyltetracarboxylic acid tetraester is predominantly produced by a process in which a phthalic acid diester is subjected to oxidative-coupling reaction in the presence of molecular oxygen and a catalyst comprising a rhodium-containing compound.
1. A process for preparing 2,3,3′,4′-biphenyl-tetracarboxylic acid tetraester which comprises subjecting a phthalic acid diester to oxidative-coupling reaction in the presence of molecular oxygen and a catalyst comprising a rhodium-containing compound represented by the following formula:
in which each R 1 and R 2 independently represents an alkyl group or an aryl group, X represents a halogen atom, and n is an integer of 1 to 3.
2. The process of claim 1 , wherein the catalyst further comprises a copper-containing compound.
3. The process of claim 2 , wherein the copper-containing compound is copper acetate.
4. The process of claim 2 , wherein the copper-containing compound is [1,3-bis(2,6-diisopropylphenyl)-imidazolium]copper(I) chloride.
5. The process of claim 1 , wherein the rhodium-containing compound is a rhodium acetylacetonato complex.
6. The process of claim 1 , wherein the catalyst further comprises β-diketone.
7. The process of claim 6 , wherein the catalyst further comprises a copper-containing compound.
8. The process of claim 1 , wherein the rhodium-containing compound is a rhodium 1,5-cyclooctadiene complex.