4,4'-Oxydiphthalic anhydride

118-45-6

1823-59-2

The general procedure for the synthesis of 4,4'-oxybisphthalic anhydride from 4-chlorophthalic anhydride is as follows: 1. 4-chlorophthalic anhydride (16 g, 87.7 mmol) was added to a 150 ml three-necked flask fitted with a distillation head, which was pre-filled with about 100 ml of distilled o-dichlorobenzene containing less than 5 ppm of water. 2. The mixture was heated to reflux for 0.5 h under nitrogen protection, followed by distillation to remove about 80 ml of o-dichlorobenzene. 3. To another flask was added powdered potassium carbonate (6.06 g, 43.8 mmol) and 50 ml of anhydrous o-dichlorobenzene. 4. The suspension was heated to reflux for 0.5 h under nitrogen protection and 40 ml of o-dichlorobenzene was distilled. 5. The 4-chlorophthalic anhydride solution prepared in step 1 was transferred to a flask containing potassium carbonate. 6. The mixture was stirred, hexaethylguanidine chloride (468 mg, 1.77 mmol, as an 18% solution in o-dichlorobenzene containing less than 15 ppm of water) was added and refluxing was continued, observing a gradual change in color of the solution to yellow. 7. The mixture was analyzed periodically and 93% yield of 4,4'-oxybisphthalic anhydride was achieved after 3 hours. 8. in a control experiment using the same molar percentage of tetraphenylphosphonium bromide and powdered potassium carbonate it took 13 hours to achieve the same yield. 9. Repeating the experiment, switching to granular potassium carbonate and adjusting the amount of hexaethylguanidine chloride to 2.0 mol% of 4-chlorophthalic anhydride, the product formation was stabilized after 3 hours in an overall yield of about 85% or better. Note: The above description and embodiments are for illustrative purposes only and should not be regarded as a limitation of the present invention. Various modifications, adaptations and substitutions may be made by those skilled in the art without departing from the spirit and scope of the present invention.