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Bond-weakening catalysis: conjugate aminations enabled by the soft homolysis of strong N-H bonds.

ABSTRACT: The ability of redox-active metal centers to weaken the bonds in associated ligands is well precedented, but has rarely been utilized as a mechanism of substrate activation in catalysis. Here we describe a catalytic bond-weakening protocol for conjugate amination wherein the strong N-H bonds in N-aryl amides (N-H bond dissociation free energies ?100 kcal/mol) are destabilized by ?33 kcal/mol upon by coordination to a reducing titanocene complex, enabling their abstraction by the weak H-atom acceptor TEMPO through a proton-coupled electron transfer process. Significantly, this soft homolysis mechanism provides a method to generate closed-shell, metalated nucleophiles under neutral conditions in the absence of a Brønsted base.

SUBMITTER: Tarantino KT

PROVIDER: S-EPMC4657442 | biostudies-literature | 2015 May

REPOSITORIES: biostudies-literature

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Bond-weakening catalysis: conjugate aminations enabled by the soft homolysis of strong N-H bonds.

Tarantino Kyle T KT Miller David C DC Callon Ted A TA Knowles Robert R RR

Journal of the American Chemical Society 20150513 20

The ability of redox-active metal centers to weaken the bonds in associated ligands is well precedented, but has rarely been utilized as a mechanism of substrate activation in catalysis. Here we describe a catalytic bond-weakening protocol for conjugate amination wherein the strong N-H bonds in N-aryl amides (N-H bond dissociation free energies ∼100 kcal/mol) are destabilized by ∼33 kcal/mol upon by coordination to a reducing titanocene complex, enabling their abstraction by the weak H-atom acce ...[more]

PMID: 25945955

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