Trimellitic anhydride → 4-(p-Isopropylbenzylidene)phthalide-6-carboxylic acid

Participants

Reaction Steps

Benzene-1,2,4-tricarboxylic anhydride and p-isopropylphenylacetic acid are reacted together as described in Example IA to give a mixture of benzylidenephthalide carboxylic acids. Fractional crystallization of this mixture from aqueous ethanol yields 2-(p-ispropylbenzylidene)phthalide-5-carboxylic acid as the less soluble isomer, and 4-(p-isopropylbenzylidene)phthalide-6-carboxylic acid as the more soluble isomer. By following the rest of the procedure set forth in part A of this example, 2-carboxy-7-isopropyl-10,11-dihydro-5-oxo-5H-dibenzo[a,d]cycloheptene was obtained with a m.p. of 178°-182° C.

Provenance & Evidence