In Water or in the Presence of Water?

摘要

Water exhibits special properties as compared to commonly employed organic solvents. For instance, Breslow and co-workers reported acceleration of the Diels–Alder reaction “in water” with the reaction performed at very high dilution to dissolve the reactants,[1] while Sharpless and co-workers described “on water”conditions under which substantial rate acceleration was observed when the organic reactants were insoluble in the aqueous phase.[2] Regardless of whether the reactants are soluble or not in water, reactions using this solvent have attracted great attention from a synthetic point of view because water is environmentally friendly and safe, and the problems of pollution that arise with organic solvents can be avoided.