Baldwin-Type Rules for Metal-Controlled Intramolecular Migratory Insertions. A Computational Study of Ni, Pd, and Pt Case

Transition metal (Ni, Pd, Pt) promoted carbocyclizations of alkenes and alkynes have been computationally investigated to rationalize the easiness or difficulty of such processes depending on the size of the forming ring. Special emphasis has been placed on measuring the activation barriers and the exo versus endo selectivities of the processes. The study leads us to propose some qualitative rules for metal controlled ring closures, noting some discrepancies with the classical Baldwin’s rules for nonmetallic cyclizations. Also, some unexpected results were found, like the extremely low activation barriers for 3-exo-dig and 3-exo-trig closures, contrasting with the scarcity of such experimental procedures, which can be computationally interpreted by the reversibility and endergonicity of cyclopropane/cyclopropene ring formation in the presence of these metals. The consistency of the present rules has been further checked by introduction of selected structural variations in the substrates.