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US 6,888,009 B2Granted
Method for the preparation of 5-carboxyphthalide
AssigneeH. Lundbeck A/S
InventorsHans Petersen, Poul Dahlberg Nielsen
Life of this patent
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Abstract
5-carboxyphthalide is obtained with very high purity and in high yields by a convenient process comprising reaction of terephthalic acid with paraformaldehyde HO(CH2)nH in oleum.
Claims16
A process for the preparation of 5-carboxyphthalide of formula A
- which comprises forming a mixture by adding formaldehyde and terephthalic acid of formula I
- to fuming sulfuric acid containing at least 18% of SO3, heating the mixture at 50-148° C. and isolating the 5-carboxyphthalide thus obtained.
Dependencies are inferred from the claim text.