Dimerization and comments on the reactivity of homophthalic anhydride

作者：Hong Julia; Wang Zheng; Levin Aaron; Emge Thomas J; Floyd David M; Knapp Spencer^*

来源：Tetrahedron Letters, 2015, 56(23): 3001-3004.

DOI：10.1016/j.tet1et.2014.10.027

• Hydrogen bonding
• Iminium reactivity
• Mannich reaction
• Decarboxylation
• N-Methylimidazole

Homophthalic anhydride (HPA) dimerizes under the influence of base to provide, sequentially, the (3-4')C-acyl dimer, a pair of chiral diastereomeric bis(lactones), 3-(2-carboxybenzyl)isocoumarin-4-carboxylic acid, and finally, 3-(2-carboxybenzyl)isocoumarin. The structures of the bis(lactones) were misassigned in 1970 based on the (presumed) cis thermal decarboxylative elimination reaction of the lower melting one. The preferred pathway should be trans anti, however, and crystallographic analysis of one of the bis(lactones) reverses the earlier assignment. The formal cycloaddition reaction of HPA with imines occurs in preference to HPA dimerization; the mechanistic implications of this reactivity difference are discussed.

• 出版日期2015-6-3
• 单位rutgers