“On Water”: Unique Reactivity of Organic Compounds in Aqueous Suspension

Water, the medium of choice: Many reactions, such as Claisen rearrangements (see scheme), are dramatically accelerated when performed in aqueous suspension (“on water”) relative to organic solvents or even neat conditions. Low miscibility of organic compounds with water is not detrimental: in fact, it facilitates the isolation of products. Water is a desirable solvent for chemical reactions for reasons of cost, safety, and environmental concerns, and the study of organic reactions in aqueous solvents has an intriguing history.1 Most notably, certain pericyclic reactions such as Diels–Alder cycloadditions2 and Claisen rearrangements3 of hydrophobic compounds have been found to be accelerated in dilute aqueous…

• NS
  National Science Foundation
• WM
  W. M. Keck Foundation
• NI
  National Institutes of Health
• NI
  National Institute of General Medical Sciences
• DO
  Division of Chemistry