A Dinickel Catalyzed Cyclopropanation without the Formation of a Metal Carbene Intermediate

Abstract

(NDI)Ni 2 catalysts (NDI = naphthyridine-diimine) promote cyclopropanation reactions of 1,3-dienes using (Me 3 Si)CHN 2 .Mechanistic studies reveal that ametal carbene intermediate is not part of the catalytic cycle.T he (NDI)Ni 2-(CHSiMe 3)complex was independently synthesized and found to be unreactive toward dienes.B ased on DFT models,w e propose an alternative mechanism that begins with aN i 2mediated coupling of (Me 3 Si)CHN 2 and the diene.N 2 extrusion followed by radical CÀCb ond formation generates the cyclopropane product. This model reproduces the experimentally observed regioselectivity and diastereoselectivity of the reaction.

Combined Experimental and Computational Study of Ruthenium N-Hydroxyphthalimidoyl Carbenes in Alkene Cyclopropanation Reactions

“…As far as we are aware, a few kinetic studies in two specific catalytic systems have been performed, , revealing that cyclopropanation can occur through both inner-sphere (IS) and outer-sphere (OS) mechanisms. Computational investigations have provided more detailed information on these pathways , and some exceptional alternatives . In the inner-sphere mechanism, a metallacyclobutane intermediate is formed upon a [2 + 2] cycloaddition between the carbene and the olefin ligands .…”

“…The outer-sphere mechanism, on the other hand, involves intermolecular reaction with the olefin either in a single step or via radical intermediates . More recent computational work has focused on catalysts that promote the outer-sphere mechanism, employing bulky ligands or dimeric metal species. , Mechanistic studies on simpler catalysts of the Ru-Pheox type are, however, still rather scarce . While previously studied copper and rhodium catalysts have only one or two coordination sites available, the situation is greatly complicated in the case of Ru-Pheox ( 2 ) due to its octahedral C 1 -symmetric environment with four inequivalent positions that could lead to different intermediates (see Scheme A).…”

Combining metal–metal cooperativity, metal–ligand cooperativity and chemical non-innocence in diiron carbonyl complexes

“…Most prominently, the group of Uyeda has demonstrated how dinickel complexes of a redox non-innocent 1,8-naphthyridinediimine-based ligand can catalyze chemical transformations with superior activity and selectivity or distinct reactivity from what is possible with mononuclear analogues. 14 This demonstrates the potential of ligand systems that can both accommodate two metal atoms in close proximity and display redox non-innocence ( Fig. 1 , top).…”

Lewis-Acid-Promoted Ligand-Controlled Regiodivergent Cycloaddition of Pd-Oxyallyl with 1,3-Dienes: Reaction Development and Origins of Selectivities

“…The π-allyl-Pd moiety then accepted intramolecular allylic attack from the enolate moiety to form carbocyclic products. In addition, we suspected that careful tuning of the structural properties of the palladium ligand might favor either 1,5- or 1,7-C–C bond formation, thus allowing us to accomplish regiodivergent cycloaddition reactions of Pd-oxyallyl species with 1,3-dienes (Scheme c). − …”