Catalytic oxygenation of organic substrates: Toward greener ways for incorporating oxygen

• Homogeneous catalytic oxidation systems based on transition metals are reviewed.
• The use of the green oxidants, H2O2 and N2O as benign oxygen sources is presented.
• Efficiency and selectivity of the oxidation systems is discussed.
• Mechanisms and possible activation pathways are analyzed.

The incorporation of oxygen to organic substrates has been matter of great interest in chemistry. With the growing concern for the environment, this reaction has also been subject of investigation to bring out more environmentally friendly systems. The use of hydrogen peroxide or nitrous oxide as oxidants can become an alternative to more pollutant compounds and, even though these generate by-products, the latter are considered benign. Besides that, the transformation of environmentally harmful chemicals, such as N2O, into more benign products, is desirable.This review summarizes the advances from the past decade in the field of homogeneous oxygenation using transition metal catalysts and H2O2 or N2O as oxygen sources. For H2O2, emphasis has been done in the contributions on oxidative functionalization of alkanes using metals from the groups 7 and 8, and the oxidation of organosulfur compounds, focused on the systems with potential to perform oxidative desulfurization and those that mediate sulfoxidation. For N2O, the activation of the oxidant at metal centers is discussed, even if the complexes do not engage yet in catalytic systems, since the coordination compounds obtained could potentially perform as catalysts in several oxygen atom transfer reactions. The main activation pathways of the oxidants, as well as the efficiency and selectivity of the systems is discussed.

This review summarizes the advances from the past decade in the field of homogeneous oxygenation using transition metal catalysts and H2O2 or N2O as oxygen sources. It is not our intent to provide a comprehensive summary of all the work described in the literature but to highlight several interesting transition metal-based catalytic systems that activate H2O2 or N2O. The use of H2O2 on the catalytic oxidative functionalization of alkanes using metals from the groups 7 and 8, and on the oxidation of organosulfur compounds, in particular oxidative desulfurization and sulfoxidation, are covered. The activation of N2O at metal centers is discussed, as well as the main reaction pathways of the oxidant, and the efficiency and selectivity of the catalytic systems involving N2O is discussed.Figure optionsDownload as PowerPoint slide