Michael Additions in Aqueous Media: "On-Water" and "In-Water" Processes from a-Nitroketones and their Anions
Résumé
A variety of α,β-unsaturated aldehydes and ketones gave very high-yielding Michael addition reactions with α-nitrocycloalkanones in water, at room temperature without added catalyst. These can be considered as one of the very few "on-water" Michael reactions known in the literature, because they took place in suspension or emulsion and at increased speed relative to the same transformations performed in organic solvents. A related protocol that uses very dilute, aqueous solutions of potassium carbonate as the reaction media extended the scope of the method to cyclic enones and unsaturated esters, nitriles and sulfones and is likely to take place in the bulk of the aqueous phase, i.e., "in-water". Both preparative methods constitute environmentally benign and efficient alternatives to previously known procedures.