Preparation of substituted phthalic anhydrides
US4560772A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 22, 1984 |
| Grant date | Dec 24, 1985 |
| Priority date | — |
| Expiry date | Oct 22, 2004 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC07C51/567
- WIPO fieldOrganic fine chemistry
- WIPO sectorChemistry
Abstract
A process for preparing substituted phthalic anhydrides, example 4-methylphthalic, in which the Diels-Alder addition product of a conjugated diene, example isoprene, and maleic anhydride is reacted with sulfur in the presence of a catalyst. The catalyst is zinc oxide and 2-mercaptobenzothiazole. This reaction is carried out at elevated temperatures. A resulting thio derivative by-product can further be reacted with water at elevated temperatures in the presence of catalytic amounts of a base to form 4-methylphthalic anhydride. This base can be sodium hydroxide or N,N,N', N'-tetramethylguanidine. o-Dichlorobenzene can be added to prevent solids distillation during the process.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.