Iron Photocatalysis for C─H Functionalizations

Photo-assisted, iron-catalyzed C─H functionalizations represent nowadays a sustainable tool to develop unprecedented transformations, unviable by common catalytic organometallic approaches promoted by transition metals. In fact, the use of this new technology allows for more efficient synthetic transformations by increasing the chemo-, regio- and site-selectivity of the catalysis while reducing the formation of by-products and shortening reaction times. Further, the replacement of precious transition-metals with iron catalysts is highly desiderable for the development of environmentally-friendly synthetic methods. Within this review, we aim to summarize the latest achievements combining the most abundant and safe transition metal in “outer-sphere” C─H functionalization reactions mediated by light for the formation of new C─C and C─Het bonds, including challenging C─N, C─P, C─B and C─S bonds. Particular attention has been directed toward the description of mechanistic aspects of the iron catalysis and the application of the synthetic methods for late-stage C─H functionalizations of polymers, marketed drugs, biologically-active compounds and materials.