Preparation of substituted phthalic anhydrides

Details Preparation of substituted phthalic anhydrides Preparation of substituted phthalic anhydrides

1984-10-22

1985-12-24

Raymond, Richard L.

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

549 54, C07D30789

Patent

active

045607729

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.

REFERENCES:
patent: 2264429 (1941-12-01), Bergmann et al.
patent: 2391226 (1945-12-01), Clifford et al.
patent: 4302396 (1981-11-01), Tsujimoto et al.
Newman et al, JACS, vol. 63 (1941) pp. 1542-1544.
Craig, JACS, vol. 72 (1950) pp. 3732-3733.
Izv. Akad. Nauk. SSSR, Ser. Khim., 6 (1973) p. 1315, English translation, p. 1271.

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