title: Dimerization and comments on the reactivity of homophthalic anhydride.
abstract: 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)cisthermal decarboxylative elimination reaction of the lower melting one. The preferred pathway should betrans-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.
authors.affiliation: Department of Chemistry and Chemical Biology, Rutgers - The State University of New Jersey, 610 Taylor Rd., Piscataway, NJ 08854, USA.
authors.forename: Julia
authors.initials: J
authors.lastname: Hong
authors.affiliation: Department of Chemistry and Chemical Biology, Rutgers - The State University of New Jersey, 610 Taylor Rd., Piscataway, NJ 08854, USA.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Chemistry and Chemical Biology, Rutgers - The State University of New Jersey, 610 Taylor Rd., Piscataway, NJ 08854, USA.
authors.forename: Aaron
authors.initials: A
authors.lastname: Levin
authors.affiliation: Department of Chemistry and Chemical Biology, Rutgers - The State University of New Jersey, 610 Taylor Rd., Piscataway, NJ 08854, USA.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Emge
authors.affiliation: Department of Chemistry and Chemical Biology, Rutgers - The State University of New Jersey, 610 Taylor Rd., Piscataway, NJ 08854, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Floyd
authors.affiliation: Department of Chemistry and Chemical Biology, Rutgers - The State University of New Jersey, 610 Taylor Rd., Piscataway, NJ 08854, USA.
authors.forename: Spencer
authors.initials: S
authors.lastname: Knapp
keywords: Decarboxylation; Hydrogen bonding; Iminium reactivity; Mannich reaction; N-Methylimidazole