Fe-catalyzed synthesis of 2-benzoxazolone - an important fragment of biologically active compounds

2-Benzoxazolone, as well as its derivatives, are valuable structural fragments of a number of important biologically active substances. Benzoxazolone derivatives are promising as antitumor, antimicrobial, antiretroviral, anticonvulsant, tranquilizing and insecticidal agents. 2-Benzoxazolone is usually produced by the condensation of o-aminophenol with urea, phosgene, and other carbonic acid derivatives. There are also methods for the synthesis of 2-benzoxazolone from salicylamide with trichloroisocyanuric acid as a chlorinating agent, from hydroxybenzoic acid using ammonium azide and Vilsmeier complex. The disadvantages of these methods are: the high cost of the initial reagents, the need to use aggressive and
toxic reagents (phosgene, ammonium azide) and complexity of hardware design for reactors. We have developed highly efficient oxidative cyclocarbonylation of 2-aminophenol to oxazolidin-2-one using FeCl_3^*6H₂O and Fe(acac)₃ as catalysts under relatively mild conditions (100–120 °C, atmospheric pressure) in the presence of CCl₄ and water. We assume that in situ formed carbon dioxide is involved into a cyclization reaction with o-aminophenol to form the target benzoxazole. The reaction takes 3-10 hours to give 2-benzoxazolone in high yield.