ABSTRACT
Dinickel naphthyridine-bis(oxazoline) catalysts promote enantioselective intermolecular [4 + 1]-cycloadditions of vinylidene equivalents and 1,3-dienes. The products of this reaction are methylenecyclopentenes, and the exocyclic alkene is generally obtained with high Z selectivity. E- and Z-dienes react in a stereoconvergent fashion, providing cycloadducts with the same sense of absolute stereochemistry and nearly identical ee values. This feature allows dienes that are commercially available as E/Z mixtures to be used as substrates for the cycloaddition. A DFT model for the origin of asymmetric induction is provided.
Subject(s)
Alkenes/chemistry , Coordination Complexes/chemistry , Naphthyridines/chemistry , Nickel/chemistry , Zinc/chemistry , Catalysis , Cycloaddition Reaction , Density Functional Theory , Models, Molecular , Molecular Structure , Oxazoles/chemistry , StereoisomerismABSTRACT
A family of low-valent Ni2, Co2, and Fe2 naphthyridine-diimine (NDI) complexes is presented. Ligand-based π* orbitals are sufficiently low-lying to fall within the metal 3d manifold, resulting in electronic structures that are highly delocalized across the conjugated [NDI]M2 system. This feature confers stability to metal-metal interactions during two-electron redox reactions, as demonstrated in a prototypical oxidative addition of allyl chloride.