THE FORMATION OF ANHYDRIDES IN THE MITSUNOBU REACTION

Treatment of benzoic acid with triphenylphosphine and diisopropyl azod icarboxylate in THF or acetonitrile, results in the formation of benzo ic anhydride. A significant solvent effect was observed for this react ion. Anhydride formation did not occur however with the more acidic p- nitrobenzoic acid. Relative rate and competition experiments suggest t hat the improved yields observed when p-nitrobenzoic acid is used inst ead of benzoic acid in the Mitsunobu esterification reaction are due t o competitive anhydride formation in the latter case. (C) 1997 Elsevie r Science Ltd.