Cyclopropanation reactions catalysed by dendrimers possessing one metalloporphyrin active site at the core: linear and sigmoidal kinetic behaviour for different dendrimer generations

Experimental and computational studies on dendrimers possessing a Fe(porphyrin) catalytic core and polyether dendritic arms show that these macromolecules promote efficiently the (2+1) cycloaddition between a model alkene and diazomethane. The reaction is kinetically efficient and competitive with smaller catalysts. Lower generations of dendrimers exhibit a normal hyperbolic kinetic behaviour, whereas third- and fourth-generation dendrimers show a sigmoidal kinetic profile, compatible with cooperative effects most likely due to aggregation phenomena. This behaviour resembles that observed for Fe(porphyrin) containing biomolecules such as cytochromes and haemoglobin. [Display omitted]