From Lossen Transposition to Solventless "medicinal Mechanochemistry"

An environmentally friendly mechanochemical strategy for the preparation of unsymmetrical ureas and 3,5-disubstituted hydantoins by using safe starting materials in place of hazardous and toxic isocyanates has been designed. For the first time, the Lossen rearrangement was successfully applied to prepare a collection of relevant structures in medicinal chemistry via a one-pot mechanochemical approach and without a single drop of organic solvent including during the workup. The procedure was effective for the preparation of the Active Pharmaceutical Ingredient (API) ethotoin.