Bromine → 4-Methylphthalic anhydride

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[CH3:1][C:2]1[CH2:3][CH:4]2[C:9](=[O:10])[O:8][C:6](=[O:7])[CH:5]2[CH2:11][CH:12]=1.[S].BrBr>C(O)(=O)C>[CH3:1][C:2]1[CH:3]=[C:4]2[C:9](=[O:10])[O:8][C:6](=[O:7])[C:5]2=[CH:11][CH:12]=1

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실험 절차

Various processes are known for preparing substituted phthalic anhydrides. In two such processes 4-methyl-1,2,3,6-tetrahydrophthalic anhydride is dehydrogenated either by sulfur or by bromine in acetic acid. Yields of 4-methylphthalic anhydride of 59 percent to 87 percent are claimed for the former method, while the latter gives only a 16 percent yield [see Izv. Akad. Nauk. SSSR, Ser. Khim., 6, 1315 (1973) English translation, page 1271 and D. Craig, Journal of American Chemical Society, Vol. 72, page 3732, (1950)].