Fe-Catalyzed Synthesis of 2-Benzoxazolone—An Important Fragment of Biologically Active Compounds

Abstract

2-Benzoxazolone, as well as its derivatives, are valuable structural fragments of a number of important biologically active substances. 2-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 the 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 the complexity of the hardware design for the reactors. We have developed the highly efficient oxidative cyclocarbonylation of 2-aminophenol to oxazolidin-2-one using FeCl3*6H2O and Fe(acac)3 as catalysts under relatively mild conditions (100–120 °C) in the presence of CCl4 and water. We assume that in situ-formed carbon dioxide is involved in a cyclization reaction with o-aminophenol to form the target 2-benzoxazole. The reaction takes 2–10 h to give 2-benzoxazolone a high yield.

Keywords

• 2-benzoxazolone
• oxazolidin-2-one
• iron catalysis
• heterocyclization
• oxidative carbonylation