LAUSR

The mechanism of the cyclopropanation of alkenes with diazocompounds catalyzed by ClFeIII–porphyrin, [ClFeII–porphyrin]−, and FeII–porphyrin has been investigated by density functional theory calculations. The obtained results indicate that the only viable catalyst is the FeII–porphyrin, whose catalytic cycle involves a stepwise multistate (singlet, triplet, and quintet spin states) mechanism. The triplet FeII–porphyrin interacts with diazomethane leading to the formation of the axial and bridged FeII–carbene complexes. The former type is favored at the singlet state, the latter is the most stable at higher states, and both conformations are accessible at the experimental conditions. The second key step of the reaction consists of the (2 + 1) cycloaddition of the axial FeII–carbene complex to yield the corresponding cyclopropane. Additionally, we have explored the possibility of catalyzing the reaction via a double incorporation of the carbene moiety into the metal coordinating sphere. The obtained result...