Phthalic Anhydride → 1,4-Phthalazinedione

Participants

Reaction Steps

When R7 and R8 are cyclopentylene or cyclohexylene, the dichloro intermediate is conveniently prepared from a 4,5,6,7-tetrahydro-4,7-(methano or ethano)isobenzofuran-1,3-dione. Diels and Alder, Ann., 478, 149 (1930); Ann., 490, 236 (1931). The dione compound is reacted with excess hydrazine hydrate in an exothermic reaction to produce the corresponding hexahydro-5,8-(methano or ethano)phthalazine-1,4-dione. Additional heating at 100°-170° C. for 10-30 minutes may be useful to complete the reaction. The phthalazine-1,4-dione is then reacted with excess phosphorus oxychloride heated at reflux for about 2-4 hours, cooled and the product hydrolyzed by careful addition of ice and water to produce the dichloro intermediate.

Provenance & Evidence