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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) 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.

SUBMITTER: Hong J

PROVIDER: S-EPMC4481714 | biostudies-literature | 2015 Jun

REPOSITORIES: biostudies-literature

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Dimerization and comments on the reactivity of homophthalic anhydride.

Hong Julia J Wang Zheng Z Levin Aaron A Emge Thomas J TJ Floyd David M DM Knapp Spencer S

Tetrahedron letters 20150601 23

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) <i>cis</i> thermal decarboxylative elimination reaction of the lower melting one. The preferred pathway should be <i>trans-anti</i>, however, and crystallo ...[more]

PMID: 26124537

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